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Abstract

This review attempts to provide some sense of our current knowledge of water including overall patterns of intake and some factors linked with intake, the complex mechanisms behind water homeostasis, the effects of variation in water intake on health and energy intake, weight, and human performance and functioning. Water represents a critical nutrient whose absence will be lethal within days. Water's importance for prevention of nutrition-related noncommunicable diseases has emerged more recently because of the shift toward large proportions of fluids coming from caloric beverages. Nevertheless, there are major gaps in knowledge related to measurement of total fluid intake, hydration status at the population level, and few longer-term systematic interventions and no published random-controlled longer-term trials. We suggest some ways to examine water requirements as a means to encouraging more dialogue on this important topic.

Keywords: water, hydration, water intake, water measurement, recommended daily intake, water adequacy

I. INTRODUCTION

Water is essential for life. From the time that primeval species ventured from the oceans to live on land, a major key to survival has been prevention of dehydration. The critical adaptations cross an array of species, including man. Without water, humans can survive only for days. Water comprises from 75% body weight in infants to 55% in elderly and is essential for cellular homeostasis and life. Nevertheless there are many unanswered questions about this most essential component of our body and our diet. This review attempts to provide some sense of our current knowledge of water including overall patterns of intake and some factors linked with intake, the complex mechanisms behind water homeostasis, the effects of variation in water intake on health and energy intake, weight, and human performance and functioning.

Recent statements on water requirements have been based on retrospective recall of water intake from food and beverages among healthy non-institutionalized individuals. We provide examples of water intake assessment in populations to clarify the need for experimental studies. Beyond these circumstances of dehydration, we do not truly understand how hydration affects health and well-being, even the impact of water intakes on chronic diseases. Recently, Jéquier and Constant addressed this question based on the human physiology. We need to know more about the extent that water intake might be important for disease prevention and health promotion.

As we note later, few countries have developed water requirements and those that do base them on weak population-level measures of water intake and urine osmolality., The European Food Safety Authority (EFSA) has been recently asked to revise existing recommended intakes of essential substances with a physiological effect including water since this nutrient is essential for life and health.

The US Dietary Recommendations for water are based on median water intakes with no use of measurements of dehydration status of the population to assist. One-time collection of blood samples for the analysis of serum osmolality has been used by NHANES. At the population level we have no accepted method of assessing hydration status and one measure some scholars use, hypertonicity, is not even linked with hydration in the same direction for all age groups. Urine indices are used often but reflect recent volume of fluid consumed rather than a state of hydration. Many scholars use urine osmolality to measure recent hydration status. ⁻ Deuterium dilution techniques (isotopic dilution with D2O or deuterium oxide) allows measurement of total body water but not water balance status. Currently we feel there are no adequate biomarkers to measure hydration status at the population level.

When we speak of water we are essentially focusing first and foremost on all types of water, be they soft or hard, spring or well, carbonated or distilled water. Furthermore we get water not only directly as a beverage but from food and to a very small extent also from oxidation of macronutrients (metabolic water). The proportion of water that comes from beverages and food varies with the proportion of fruits and vegetables in the diet. We present the ranges of water in various foods (). In the United States it is estimated that about 22% of water comes from our food intake while it would be much higher in European countries, particularly a country like Greece with its higher intake of fruits and vegetables or South Korea., , The only in-depth study of water use and water intrinsic to food in the US found a 20.7% contribution from food water;, however as we show later, this research was dependent on poor overall assessment of water intake.

Table 1

90-99%

Fat-free milk, cantaloupe, strawberries, watermelon, lettuce, cabbage, celery, spinach, pickles, squash (cooked)

80-89%

Fruit juice, yogurt, apples, grapes, oranges, carrots, broccoli (cooked), pears, pineapple

70-79%

Bananas, avocados, cottage cheese, ricotta cheese, potato (baked), corn (cooked), shrimp

60-69%

Pasta, legumes, salmon, ice cream, chicken breast

50-59%

Ground beef, hot dogs, feta cheese, tenderloin steak (cooked)

30-39%

Cheddar cheese, bagels, bread

20-29%

Pepperoni sausage, cake, biscuits

10-19%

Butter, margarine, raisins

1-9%

Walnuts, peanuts (dry roasted), chocolate chip cookies, crackers, cereals, pretzels, taco shells, peanut butter

This review considers water requirements in the context of recent efforts to assess water intake in US populations. Relationship of water and calorie intake is explored both for insights into the possible displacement of calories from sweetened beverages by water and also to examine the possibility that water requirements would be better expressed in relation to calorie/energy requirements with the dependence of the latter on age, size, gender, and physical activity level. We review current understanding of the exquisitely complex and sensitive system which protects land animals against dehydration and comment on the complications of acute and chronic dehydration in man against which a better expression of water requirements might complement the physiological control of thirst. Indeed, the fine intrinsic regulation of hydration and water intake in individuals mitigates against prevalent underhydration in populations and effects on function and disease.

Regulation of fluid intake

To prevent dehydration reptiles, birds, vertebrates, and all land animals have evolved an exquisitely sensitive network of physiological controls to maintain body water and fluid intake by thirst. Humans may drink for various reasons, particularly for hedonic ones but most of drinking is due to water deficiency which triggers the so called regulatory or physiological thirst. The mechanism of thirst is quite well understood today and the reason non-regulatory drinking is often encountered is related to the large capacity of kidneys to rapidly eliminate excesses of water or reduce urine secretion to temporarily economize on water. But this excretory process can only postpone the necessity for drinking or for stopping drinking an excess of water. Non regulatory drinking is often confusing, particularly in wealthy societies facing highly palatable drinks or fluids that contain other substance that the drinker seeks. The most common of them are sweeteners or alcohol to which water is served as a vehicle. Drinking these beverages isn't due to excessive thirst or hyperdipsia as it can be shown by offering pure water instead and finding out that the same drinker is in fact hypodipsic (Characterized by abnormally diminished thirst).

Fluid balance of the two compartments

Maintaining a constant water and mineral balance requires the coordination of sensitive detectors at different sites in the body linked by neural pathways with integrative centers in the brain that process this information. These centers are also sensitive to humoral factors (neurohormones) produced for the adjustment of diuresis, natriuresis and blood pressure (angiotensin mineralocorticoids, vasopressin, atrial natriuretic factor). Instructions from the integrative centers to the "executive organs" (kidney, sweat glands and salivary glands) and to the part of the brain responsible for corrective actions such as drinking are conveyed by certain nerves in addition to the above mentioned substances.

Most of the components of fluid balance are controlled by homeostatic mechanisms responding to the state of body water. These mechanisms are sensitive and precise, and are activated with deficits or excesses of water amounting to only a few hundred milliliters. A water deficit produces an increase in the ionic concentration of the extracellular compartment, which takes water from the intracellular compartment causing cells to shrink. This shrinkage is detected by two types of brain sensors, one controlling drinking and the other controlling the excretion of urine by sending a message to the kidneys mainly via the antidiuretic hormone vasopressin to produce a smaller volume of more concentrated urine. When the body contains an excess of water, the reverse processes occur: the lower ionic concentration of body fluids allows more water to reach the intracellular compartment. The cells imbibe, drinking is inhibited and the kidneys excrete more water.

The kidneys thus play a key role in regulating fluid balance. As discussed later, the kidneys function more efficiently in the presence of an abundant water supply. If the kidneys economize on water, producing a more concentrated urine, these is a greater cost in energy and more wear on their tissues. This is especially likely to occur when the kidneys are under stress, for example when the diet contains excessive amounts of salt or toxic substances that need to be eliminated. Consequently, drinking enough water helps protect this vital organ.

Regulatory drinking

Most drinking obeys signals of water deficit. Apart from urinary excretion, the other main fluid regulatory process is drinking, mediated through the sensation of thirst. There are two distinct mechanisms of physiological thirst: the intracellular and the extracellular mechanisms. When water alone is lost, ionic concentration increases. As a result, the intracellular space yields some of its water to the extracellular compartment. One again, the resulting shrinkage of cells is detected by brain receptors that send hormonal messages to induce drinking. This association with receptors that govern extracellular volume is therefore accompanied by an enhancement of salt appetite. Thus, people who have been sweating copiously prefer drinks that are relatively rich in Na+ salts rather than pure water. As previously mentioned, it is always important to supplement drinks with additional salt when excessive sweating is experienced.

The brain's decision to start or stop drinking and to choose the appropriate drink is made before the ingested fluid can reach the intra- and extracellular compartments. The taste buds in the mouth send messages to the brain about the nature, and especially the salt of the ingested fluid, and neuronal responses are triggered as if the incoming water had already reached the bloodstream. These are the so-called anticipatory reflexes: they cannot be entirely "cephalic reflexes" because they arise from the gut as well as the mouth.

The anterior hypothalamus and pre-optic area are equipped with osmo-receptors related to drinking. Neurons in these regions show enhanced firing when the inner milieu gets hyperosmotic. Their firing decreases when water is loaded in the carotid artery that irrigates the neurons. It is remarkable that the same decrease in firing in the same neurons takes place when the water load is applied on the tongue instead of being injected in the carotid artery. This anticipatory drop in firing is due to a mediation neural pathways departing from the mouth and by converging on to the neurons which simultaneously sense of the inner milieu (blood).

Non-regulatory drinking

Although everyone experiences thirst from time to time, it plays little day-to-day role in the control of water intake in healthy people living in temperate climates. We generally consume fluids not to quench our thirst, but as components of everyday foods (e.g. soup, milk), as beverages used as mild stimulants (tea, coffee) and for pure pleasure. As common example is alcohol consumption which can increase individual pleasure and stimulate social interaction. Drinks are also consumed for their energy content, as in soft drinks and milk, and are used in warm weather for cooling and in cold weather for warming. Such drinking seems also to be mediated through the taste buds, which communicate with the brain in a kind of "reward system" the mechanisms of which are just beginning to be understood. This bias in the way human beings rehydrate themselves may be advantageous because it allows water losses to be replaced before thirst-producing dehydration takes place. Unfortunately, this bias also carries some disadvantages. Drinking fluids other than water can contribute to an intake of caloric nutrients in excess of requirements, or in alcohol consumption that in some people may insidiously bring about dependence. For example, total fluid intake increased from 79 fluid ounces in 1989 to 100 fluid ounces in 2002 among US adults, all from caloric beverages.

Effects of aging on fluid intake regulation

The thirst and fluid ingestion responses of older persons to a number of stimuli have been compared to those seen in younger persons. Following water deprivation older persons are less thirsty and drink less fluid compared to younger persons., The decrease in fluid consumption is predominantly due to a decrease in thirst as the relationship between thirst and fluid intake is the same in young and old persons. Older persons drink insufficient water following fluid deprivation to replenish their body water deficit. When dehydrated older persons are offered a highly palatable selection of drinks, this also failed to result in an increased fluid intake. The effects of increased thirst in response to an osmotic load have yielded variable responses with one group reporting reduced osmotic thirst in older individuals and one failing to find a difference. In a third study, young individuals ingested almost twice as much fluid as old persons, despite the older subjects having a much higher serum osmolality.

Overall these studies support small changes in the regulation of thirst and fluid intake with aging. Defects in both osmoreceptors and baroreceptors appear to exist as well as changes in the central regulatory mechanisms mediated by opioid receptors. Because of their low water reserves, it may be prudent for the elderly to learn to drink regularly when not thirsty and to moderately increase their salt intake when they sweat. Better education on these principles may help prevent sudden hypotension and stroke or abnormal fatigue can lead to a vicious circle and eventually hospitalization.

Thermoregulation

Hydration status is critical to the body's process of temperature control. Body water loss through sweat is an important cooling mechanism in hot climates and in physical activity. Sweat production is dependent upon environmental temperature and humidity, activity levels, and type of clothing worn. Water losses via skin (both insensible perspiration and sweating) can range from 0.3 L/h in sedentary conditions to 2.0 L/h in high activity in the heat and intake requirements range from 2.5 to just over 3 L/d in adults under normal conditions, and can reach 6 L/d with high extremes of heat and activity., Evaporation of sweat from the body results in cooling of the skin. However, if sweat loss is not compensated for with fluid intake, especially during vigorous physical activity, a hypohydrated state can occur with concomitant increases in core body temperature. Hypohydration from sweating results in a loss in electrolytes, as well as a reduction in plasma volume, and can lead to increased plasma osmolality. During this state of reduced plasma volume and increased plasma osmolality, sweat output becomes insufficient to offset increases in core temperature. When fluids are given to maintain euhydration, sweating remains an effective compensation for increased core temperatures. With repeated exposure to hot environments, the body adapts to heat stress, and cardiac output and stroke volume return to normal, sodium loss is conserved, and the risk for heat-stress related illness is reduced. Increasing water intake during this process of heat acclimatization will not shorten the time needed to adapt to the heat, but mild dehydration during this time may be of concern and is associated with elevations in cortisol, increased sweating, and electrolyte imbalances.

Children and the elderly have differing responses to ambient temperature and different thermoregulatory concerns than healthy adults. Children in warm climates may be more susceptible to heat illness than adults due to greater surface area to body mass ratio, lower rate of sweating, and slower rate of acclimatization to the heat., Children may respond to hypohydration during activity with a higher relative increase in core temperature than adults do, and sweat less, thus losing some of the benefits of evaporative cooling. However, it has been argued that children can dissipate a greater proportion of body heat via dry heat loss, and the concomitant lack of sweating provides a beneficial means of conserving water under heat stress. Elders, in response to cold stress, show impairments in thermoregulatory vasoconstriction and body water is shunted from plasma into the interstitial and intracellular compartments., With respect to heat stress, water lost through sweating decreases water content of plasma, and the elderly are less able to compensate for increased blood viscosity. Not only do they have a physiological hypodipsia, but this can be exaggerated by central nervous system disease and by dementia . In addition, illness and limitations in activities of daily living can further limit fluid intake. Coupled with reduced fluid intake, with advancing age there is a decrease in total body water. Older individuals have impaired renal fluid conservation mechanisms and, as noted above, have impaired responses to heat and cold stress , . All of these factors contribute to an increased risk of hypohydration and dehydration in the elderly.

II. PHYSIOLOGICAL EFFECTS OF DEHYDRATION

In this section, the role of water in health is generally characterized in terms of deviations from an ideal hydrated state, generally in comparison to dehydration. The concept of dehydration encompasses both the process of losing body water and also the state of dehydration. Much of the research on water and physical or mental functioning compares a euhydrated state, usually achieved by provision of water sufficient to overcome water loss, to a dehydrated state, which is achieved via withholding of fluids over time and during periods of heat stress or high activity. In general, provision of water is beneficial in those with a water deficit, but little research supports the notion that additional water in adequately hydrated individuals confers any benefit.

Physical performance

The role of water and hydration in physical activity, particularly in athletes and in the military, has been of considerable interest and is well-described in the scientific literature. ⁻ During challenging athletic events, it is not uncommon for athletes to lose 6-10% of body weight in sweat loss, thus leading to dehydration if fluids have not been replenished. However, decrements in physical performance in athletes have been observed under much lower levels of dehydration, as little as 2%. Under relatively mild levels of dehydration, individuals engaging in rigorous physical activity will experience decrements in performance related to reduced endurance, increased fatigue, altered thermoregulatory capability, reduced motivation, and increased perceived effort., Rehydration can reverse these deficits, and also reduce oxidative stress induced by exercise and dehydration. Hypohydration appears to have a more significant impact on high-intensity and endurance activity such as tennis and long-distance running than on anaerobic activities such as weight lifting or on shorter-duration activities, such as rowing.

During exercise, individuals may not hydrate adequately when allowed to drink according to thirst. After periods of physical exertion, voluntary fluid intake may be inadequate to offset fluid deficits. Thus, mild to moderate dehydration can therefore persist for some hours after the conclusion of physical activity. Research in athletes suggests that, principally at the beginning of the season, they are at particular risk for dehydration due to lack of acclimatization to weather conditions or suddenly increased activity levels., A number of studies show that performance in temperate and hot climates is affected to a greater degree than performance in cold temperatures., , Exercise in hot conditions with inadequate fluid replacement is associated with hyperthermia, reduced stroke volume and cardiac output, decreases in blood pressure, and reduced blood flow to muscle.

During exercise, children may be at greater risk for voluntary dehydration. Children may not recognize the need to replace lost fluids, and both children as well as coaches need specific guidelines for fluid intake. Additionally, children may require longer acclimation to increases in environmental temperature than do adults., Recommendations are for child athletes or children in hot climates to begin athletic activities in a well-hydrated state and to drink fluids over and above the thirst threshold.

Cognitive performance

Water, or its lack (dehydration), can influence cognition. Mild levels of dehydration can produce disruptions in mood and cognitive functioning. This may be of special concern in the very young, very old, those in hot climates, and those engaging in vigorous exercise. Mild dehydration produces alterations in a number of important aspects of cognitive function such as concentration, alertness and short-term memory in children (10-12 y), young adults (18-25y) ⁻ and in the oldest adults, 50-82y. As with physical functioning, mild to moderate levels of dehydration can impair performance on tasks such as short-term memory, perceptual discrimination, arithmetic ability, visuomotor tracking, and psychomotor skills. ⁻ However, mild dehydration does not appear to alter cognitive functioning in a consistent manner., , , In some cases, cognitive performance was not significantly affected in ranges from 2-2.6% dehydration., Comparing across studies, performance on similar cognitive tests was divergent under dehydration conditions., In studies conducted by Cian and colleagues,, participants were dehydrated to approximately 2.8% either through heat exposure or treadmill exercise. In both studies, performance was impaired on tasks examining visual perception, short-term memory, and psychomotor ability. In a series of studies using exercise in conjunction with water restriction as a means of producing dehydration, D'Anci and colleagues observed only mild decrements in cognitive performance in healthy young men and women athletes. In these experiments, the only consistent effect of mild dehydration was significant elevations of subjective mood score, including fatigue, confusion, anger, and vigor. Finally, in a study using water deprivation alone over a 24-h period, no significant decreases in cognitive performance were seen with 2.6% dehydration . It is possible therefore, that heat-stress may play a critical role in the effects of dehydration on cognitive performance.

Reintroduction of fluids under conditions of mild dehydration can reasonably be expected to reverse dehydration-induced cognitive deficits. Few studies have examined how fluid reintroduction may alleviate dehydration's negative effects on cognitive performance and mood. One study examined how water ingestion affected arousal and cognitive performance in young people following a period of 12-h water restriction. While cognitive performance was not affected by either water restriction or water consumption, water ingestion affected self-reported arousal. Participants reported increased alertness as a function of water intake. Rogers and coworkers observed a similar increase in alertness following water ingestion in both high- and low-thirst participants. Water ingestion, however, had opposite effects on cognitive performance as a function of thirst. High-thirst participants' performance on a cognitively demanding task improved following water ingestion, but low-thirst participants' performance declined. In summary, hydration status consistently affected self-reported alertness, but effects on cognition were less consistent.

Several recent studies have examined the utility of providing water to school children on attentiveness and cognitive functioning in children. ⁻ In these experiments, children were not fluid restricted prior to cognitive testing, but were allowed to drink as usual. Children were then provided with a drink or no drink 20-45 minutes before the cognitive test sessions. In the absence of fluid restriction and without physiological measures of hydration status, the children in these studies should not be classified as dehydrated. Subjective measures of thirst were reduced in children given water, and voluntary water intake in children varied from 57 ml to 250 ml. In these studies, as in the studies in adults, the findings were divergent and relatively modest. In the research led by Edmonds and colleagues,, children in the groups given water showed improvements in visual attention. However, effects on visual memory were less consistent, with one study showing no effects of drinking water on a spot-the-difference task in 6-7 year old children and the other showing a significant improvement in a similar task in 7-9 year old children In the research described by Benton and Burgess, memory performance was improved by provision of water but sustained attention was not altered with provision of water in the same children.

Taken together these studies indicate that low to moderate dehydration may alter cognitive performance. Rather than indicating that the effects of hydration or water ingestion on cognition are contradictory, many of the studies differ significantly in methodology and in measurement of cognitive behaviors. These variances in methodology underscore the importance of consistency when examining relatively subtle chances in overall cognitive performance. However, in those studies in which dehydration were induced, most combined heat and exercise, thus it is difficult to disentangle the effects of dehydration on cognitive performance in temperate conditions, from the effects of heat and exercise. Additionally, relatively little is known about the mechanism of mild dehydration's effects on mental performance. It has been proposed that mild dehydration acts as a physiological stressor which competes with and draws attention from cognitive processes. However, research on this hypothesis is limited and merits further exploration.

Dehydration and delirium

Dehydration is a risk factor for delirium and delirium presenting as dementia in the elderly and in the very ill. ⁻ Recent work shows that dehydration is one of several predisposing factors in observed confusion in long-term care residents, although in this study daily water intake was used as a proxy measure for dehydration rather than other, more direct clinical assessments such as urine or plasma osmolality. Older people have been reported as having reduced thirst and hypodypsia relative to younger people. In addition, fluid intake and maintenance of water balance can be complicated by factors such as disease, dementia, incontinence, renal insufficiency, restricted mobility, and drug side effects. In response to primary dehydration, older people have less thirst sensation and reduced fluid intakes in comparison to younger people. However, in response to heat stress, while older people still display a reduced thirst threshold, they do ingest comparable amounts of fluid as younger people.

Gastrointestinal function

Fluids in the diet are generally absorbed in the proximal small intestine, and absorption rate is determined by the rate of gastric emptying to the small intestine. Therefore, the total volume of fluid consumed will eventually be reflected in water balance, but the rate at which rehydration occurs is dependent upon factors which affect the rate of delivery of fluids to the intestinal mucosa. Gastric emptying rate is generally accelerated by the total volume consumed and slowed by higher energy density and osmolality. In addition to water consumed in food (1 L/d) and beverages (~2-3 L/d), digestive secretions account for a far greater portion of water that passes through and is absorbed by the gastrointestinal tract (~8 L/d). The majority of this water is absorbed by the small intestine, with a capacity of up to 15 L/d with the colon absorbing some 5 L/d.

Constipation, characterized by slow gastrointestinal transit, small, hard stools, and difficulty in passing stool, has a number of causes including medication use, inadequate fiber intake, poor diet, and illness. Inadequate fluid consumption is touted as a common culprit in constipation, and increasing fluid intake is a frequently recommended treatment. Evidence suggests, however, that increasing fluids is only of usefulness in individuals in a hypohydrated state, and is of little utility in euhydrated individuals. In young children with chronic constipation, increasing daily water intake by 50% did not affect constipation scores. For Japanese women with low fiber intake, concomitant low water intake in the diet is associated with increased prevalence of constipation. In older individuals, low fluid intake is a predictor for increased levels of acute constipation, with those consuming the least amount of fluid having over twice the frequency of constipation episodes than those consuming the most fluid. In one trial, researchers compared the utility of carbonated mineral water in reducing functional dyspepsia and constipation scores to tap water in individuals with functional dyspepsia. When comparing carbonated mineral water to tap water, participants reported improvements in subjective gastric symptoms, but there were no significant improvements in gastric or intestinal function. The authors indicate that it is not possible to determine to what degree the mineral content of the two waters contributed to perceived symptom relief, as the mineral water contained greater levels of magnesium and calcium than the tap water. The available evidence suggests that increased fluid intake should only be indicated in individuals in a hypohydrated state.,

Significant water loss can occur through the gastrointestinal tract, and this can be of great concern in the very young. In developing countries, diarrheal diseases are a leading cause of death in children resulting in approximately 1.5-2.5 million deaths per year. Diarrheal illness results not only in a reduction in body water, but also in potentially lethal electrolyte imbalances. Mortality in such cases can many times be prevented with appropriate oral rehydration therapy, by which simple dilute solutions of salt and sugar in water can replace fluid lost by diarrhea. Many consider application of oral rehydration therapy to be one of the signal public health developments of the last century.

Kidney function

As noted above, the kidney is crucial in regulating water balance and blood pressure as well as removing waste from the body. Water metabolism by the kidney can be classified into regulated and obligate. Water regulation is hormonally mediated, with the goal of maintaining a tight range of plasma osmolality between 275 to 290 mOsm/kg. Increases in plasma osmolality, and activation of osmoreceptors (intracellular) and baroreceptors (extracellular) stimulate hypothalamic release of arginine vasopressin (AVP). AVP acts at the kidney to decrease urine volume and promote retention of water, and the urine becomes hypertonic. With decreased plasma osmolality, vasopressin release is inhibited, and the kidney increases hypotonic urinary output.

In addition to regulating fluid balance, the kidneys require water for the filtration of waste from the blood stream and excretion via urine. Water excretion via the kidney removes solutes from the blood, and a minimum obligate urine volume is required to remove the solute load with a maximum output volume of 1 L/h. This obligate volume is not fixed, but is dependent upon the amount of metabolic solutes to be excreted and levels of AVP. Depending on the need for water conservation, basal urine osmolality ranges from 40 mOsm/kg up to a maximum of 1400 mOsm/kg. The ability to both concentrate and dilute urine decreases with age, with a lower value of 92 mOsm/kg and an upper range falling between 500-700 mOsm/kg for individuals over 70. ⁻ Under typical conditions, in an average adult, urine volume of 1.5 to 2.0 L/d would be sufficient to clear a solute load of 900 to 1200 mOsm/d. During water conservation and the presence of AVP, this obligate volume can decrease to 0.75-1.0 L/d and during maximal diuresis can require up to 20 L/d to remove the same solute load., , In cases of water loading, if the volume of water ingested cannot be compensated for with urine output, having overloaded the kidney's maximal output rate, an individual can enter a hyponatremic state as described above.

Heart function and hemodynamic response

Blood volume, blood pressure, and heart rate are closely linked. Blood volume is normally tightly regulated by matching water intake and water output, as described in the section on kidney function. In healthy individuals, slight changes in heart rate and vasoconstriction act to balance the effect of normal fluctuations in blood volume on blood pressure. Decreases in blood volume can occur, through blood loss (or blood donation), or loss of body water through sweat, as seen with exercise. Blood volume is distributed differently relative to the position of the heart whether supine or upright, and moving from one position to the other can lead to increased heart rate, a fall in blood pressure and, in some cases, lead to syncope. This postural hypotension (or orthostatic hypotension) can be mediated by drinking 300-500 ml of water., Water intake acutely reduces heart rate and increases blood pressure in both normotensive and hypertensive individuals. These effects of water intake on the pressor effect and heart rate occur within 15-20 minutes of drinking water and can last for up to 60 minutes. Water ingestion is also beneficial in preventing vasovagal reaction with syncope in blood donors at high risk for post-donation syncope. The effect of water drinking in these situations is thought to be due to effects on the sympathetic nervous system rather than to changes in blood volume., Interestingly, in rare cases, individuals may experience bradycardia and syncope after swallowing cold liquids. ⁻ While swallow syncope can be seen with other substances than water, swallow syncope further supports the notion that the result of water ingestion in the pressor effect has both a neural component as well as a cardiac component.

Headache

Water deprivation and dehydration can lead to the development of headache. Although this observation is largely unexplored in the medical literature, some observational studies indicate that water deprivation, in addition to impairing concentration and increasing irritability, can serve as a trigger for migraine and also prolong migraine., In those with water deprivation-induced headache, ingestion of water provided relief from headache in most individuals within 30 min to 3 h. It is proposed that water deprivation-induced headache is the result of intracranial dehydration and total plasma volume. Although provision of water may be useful in relieving dehydration related headache, the utility of increasing water intake for the prevention of headache is less well documented.

The folk wisdom that drinking water can stave off headaches has been relatively unchallenged, and has more traction in the popular press than in the medical literature. Recently, one study examined increased water intake and headache symptoms in headache patients. In this randomized trial, patients with a history of different types of headache, including migraine and tension headache, were either assigned to a placebo condition (a non-drug tablet) or the increased water condition. In the water condition, participants were instructed to consume an additional volume of 1.5 L water/day on top of what they already consumed in foods and fluids. Water intake did not affect number of headache episodes, but was modestly associated with reduction in headache intensity and reduced duration of headache. The data from this study suggest that water is limited as prophylaxis in headache sufferers, and the ability of water to reduce or prevent headache in a broader population remains unknown.

Skin

One of the more pervasive myths regarding water intake is the improvement of the skin or complexion. By improvement, it is generally understood that individuals are seeking to have a more "moisturized" look to the surface skin, or to minimize acne or other skin conditions. Numerous lay sources such as beauty and health magazines as well as the Internet suggest that drinking 8-10 glasses of water a day will "flush toxins from the skin" and "give a glowing complexion" despite a general lack of evidence, to support these proposals. The skin, however, is important in maintaining body water levels and preventing water loss into the environment.

The skin contains approximately 30% water, which contributes to plumpness, elasticity, and resiliency. The overlapping cellular structure of the stratum corneum and lipid content of the skin serves as "waterproofing" for the body. Loss of water through sweat is not indiscriminate across the total surface of the skin, but is carried out by eccrine sweat glands, which are evenly distributed over most of the body surface. Skin dryness is usually associated with exposure to dry air, prolonged contact with hot water and scrubbing with soap (both strip oils from the skin), medical conditions and medications. While more serious levels of dehydration can be reflected in reduced skin turgor,, with tenting of the skin as a flag for dehydration, overt skin turgor in individuals with adequate hydration is not altered. Water intake, particularly in individuals with low initial water intake, can improve skin thickness and density as measured by sonogram, and offsets transepidermal water loss, and can improve skin hydration. Adequate skin hydration, however, is not sufficient to prevent wrinkles or other signs of aging, which are related to genetics, and sun and environmental damage. Of more utility to individuals already consuming adequate fluids, the use of topical emollients will improve skin barrier function and improve the look and feel of dry skin.,

Hydration and chronic diseases

Many chronic diseases have multifactorial origins. In particular, differences in lifestyle and the impact of environment are known to be involved and constitute risk factors that are still being evaluated. Water is quantitatively the most important nutrient. In the past, scientific interest with regard to water metabolism was mainly directed toward the extremes of severe dehydration and water intoxication. There is evidence, however, that mild dehydration may also account for some morbidities., There is currently no consensus on a "gold standard" for hydration markers, particularly for mild dehydration. As a consequence, the effects of mild dehydration on the development of several disorders and diseases have not been well documented.

There is strong evidence showing that good hydration reduces the risk of urolithiasis (See for evidence categories). Less strong evidence links good hydration with reduced incidence of constipation, exercise asthma, hypertonic dehydration in the infant, and hyperglycemia in diabetic ketoacidosis. Good hydration is associated with a reduction in urinary tract infections, hypertension, fatal coronary heart disease, venous thromboembolism, and cerebral infarct but all these effects need to be confirmed by clinical trials. For other conditions such as bladder or colon cancer, evidence of a preventive effect of maintaining good hydration is not consistent (see ).

Table 2

Table 3

Diabetic Hyper glycemia and Ketoacidosis

Less strong

In diabetics, experimentally induced dehydration promotes development of hyperglycemia.
Higher serum osmolality at time of hospital admission was the most important predictor of death in children with diabetic ketoacidosis.

Cerebral Infarct (Stroke)

Weaker

Increased serum osmolality or hematocrit is associated with increased risk of stroke morbidity/mortality., Stroke patients with initial mid-range hematocrit have better discharge outcomes.

III. Water consumption and requirements and relationships to total energy intake

Water consumption, water requirements and energy intake are linked in fairly complex ways. This is partially because physical activity and energy expenditures affect the need for water but also because a large shift in beverage consumption over the past century or more has led to consumption of a significant proportion of our energy intake from caloric beverages. Nonregulatory beverage intake, as noted earlier, has assumed a much greater role for individuals. In this section we first review current patterns of water intake, then refer to a full meta-analysis of the effects of added water on energy intake. This includes adding water to the diet and water replacement for a range of caloric and diet beverages, including sugar-sweetened beverages, juice, milk, and diet beverages. The third component is a discussion of water requirements and suggestions for considering the use of ml water/kcal energy intake as a metric.

A. Patterns and trends of water consumption

Measurement of total fluid water consumption in free-living individuals is fairly new in focus. As a result, the state of the science is poorly developed, data are most likely fairly incomplete, and adequate validation of the measurement techniques used are not available. We first present varying patterns and trends of water intake for the United States over the past three decades and review briefly the work on water intake in Europe.

We have really no information to allow us to assume that consumption of water alone or beverage containing water affects hydration differentially., Some epidemiological data suggests water might have differential metabolic effects when consumed as water alone rather than water contained in caffeinated or flavored or sweetened beverages but these data are at best suggestive of an issue deserving of exploration., We do show below from the research of Ershow that beverages not consisting of solely water do contain less than 100% water.

One study in the United States has attempted to examine all the sources of water in our diet., These data are cited in as the Ershow study and were based on National Food Consumption Survey food and fluid intake data from 1977-78. These data are presented in for children 2-18 (Panel A) and for adults 19 and older (Panel B). Ershow and colleagues spent a great deal of time working out ways to convert USDA dietary data into water intake, including water absorbed during the cooking process, water in food, and all sources of drinking water.,

Table 4

Panel A. The Amount of Beverages Consumed in Milliliters per Capita for Children Panel B. The Amount of Beverages Consumed in Milliliters per Capita for Adults

These created a number of categories and used a range of factors measured in other studies to estimate the water categories. The water that is found in food, based on food composition table data, was 393ml for children. The water that was added as a result of cooking (e.g., rice) was 95 ml. That consumed as a beverage directly as water was 624 ml. The water found in other fluids as noted comprised the remainder of the ml with the most water coming from whole fat milk and juices (506 ml). There is a small discrepancy between the Ershow total fluid intake measures for these children and that of the normal USDA figure. That is because USDA does not remove milk fats and solids, fiber and other food constituents found in beverages, particularly, juice and milk.

A key point to be seen in these nationally representative US data is enormous variability in the amount of water consumed between survey waves (see which highlights that large variation in water intake measured in these surveys). Although adult and child water intake moved up and down at the same time, for reasons we cannot explain, the variation is greater among children than adults. This is partly that the questions asked have varied and there has not been detailed probing for water intake as the focus has been on obtaining measures of macro-and micronutrients. Dietary survey methods in the past have focused on obtaining foods and beverages containing nutrient and nonnutritive sweeteners but not on water. Related are the huge differences between the NHANES 1988-1994 and 1999 and later surveys and the USDA surveys. In addition even the NHANES1999-2002 and the 2003-6 surveys differ greatly. This represents a shift in mode of questioning to inclusion of water intake as part of a standard 24-hour recall rather than as standalone questions. Water was not even measured in 1965, and the way the questions have been asked and the limitation on probes for water intake are very clear from a review of the questionnaires plus these data. Essentially in the past people were asked how much water they consumed in a day and now they are asked these questions as part of a 24-hour recall survey. However, unlike other caloric and diet beverages, there are limited probes for water. These must be viewed as crude approximations of total water intake without any strong research to show if they are over- or underestimated. We know from our own research with several studies of water and two on-going random controlled trials that probes that include consideration of all beverages including water as a separate item provide more complete data.

Water consumption data for Europe are collected far more selectively than even the crude water intake questions from NHANES. The recent EFSA report provides measures of water consumption from a range of studies in Europe., , , Essentially what these studies show is that total water intake is lower across Europe than the United States. As with the United States data, none are based on long-term carefully measured or even repeated 24-hour recall measures of water intake from food and beverages. In unpublished work Popkin and Jebb are examining water intake in UK adults in 1986-87 and 2001-2. Their intake increased by 226 ml/d over this time period but still is only 1787 ml/d in the latter period, far below the US figure for 2005-6 of 2793 or earlier figures for comparably aged adults.

There are a few studies in the US and Europe that utilize 24-hour urine and serum osmolality measures to determine total water turnover and this measure of hydration status. These studies suggest that US adults consume over 2100 ml of water per day while those from Europe consume less than a half liter or more., Data on total urine collection would appear to be another useful measure for examining total water intake. Of course few studies aside from the Donald adolescent cohort in Germany have collected such data on population levels for large samples.

B. The effects of water consumption on overall energy intake

There is an extensive literature that focuses on the impact of sugar-sweetened beverages on weight and risk of obesity, diabetes and heart disease; however the perspective of providing more water and its impact on health has not been examined. The water literature does not address portion sizes but rather focuses mainly on water ad libitum or in selected portions compared with other caloric beverages. Elsewhere we have prepared a detailed meta-analysis of the effects of water intake alone (adding additional water), replacing sugar-sweetened beverages, juice, milk and diet beverages.

In general, the results of this review suggest that water, when replacing sugar-sweetened beverages, juice and milk is linked with reduced energy intake. This comes mainly from the clinical feeding studies but also from one very good random controlled school intervention and several other epidemiological and intervention studies. Aside from portion sizes, there are issues of timing of the beverage intake and meals (delay time from the beverage to the meal) and types of caloric sweeteners that remain to be considered. However when beverages are consumed in a normal free-living situations where 5-8 eating occasions are the norm, the delay time from the beverage to the meal may matter less. ⁻

The literature on children is extremely limited as it relates to water intake. However, the excellent German school intervention with water would suggest the effects of water on overall energy intake of children might be comparable to that of adults. In this German study children were educated on the value of water and provided in school with special filtered drinking fountains and water bottles. The intervention school children increased by 1.1 glasses/day (P<0.001) and reduced their risk of overweight by 31% (OR=0.69, P=0.40).

C. Water requirements: Evaluation of the adequacy of water intake

Classically, water data are examined in terms of milliliters (or some other measure of water volume consumed per capita per day by age group). This measure does not link fluid and caloric intake. Disassociation of fluid and calorie intake difficult for clinicians dealing with an older person who has reduced caloric intake. This ml water measure assumes some mean body size (or surface area) and a mean level of physical activity - both determinants of not only energy expenditure, but also of water balance. Children are dependent on adults for access to water and studies suggest that a larger surface area to volume ratio makes them susceptible to changes in skin temperatures, linked with ambient temperature shifts. One option utilized by some scholars is to explore in ml/kcal of food and beverage intake as was done in the 1989 US RDAs., This is an option interpretable for clinicians and does incorporate in some sense body size or surface area and activity. It has one disadvantage, namely that water as consumed with caloric beverages, affects both the numerator and denominator; however we do not know a measure that could be independent of this direct effect on body weight and/or total caloric intake.

Despite its critical importance in health and nutrition, as noted earlier, the array of available research that serves as a basis for determining requirements for water or fluid intake, or even rational recommendations for populations, is limited compared to most other nutrients. While this deficit may be partly explained by the highly sensitive set of neurophysiological adaptations and adjustments that occur over a large range of fluid intake to protect body hydration and osmolarity, this deficit remains a challenge for the nutrition and public health community. The latest official effort at recommending water intake for different subpopulations was a part of the Dietary Reference Intake process of the Institute of Medicine of the National Academy of Science's Report on Dietary Reference Intakes on Water and Electrolytes as reported in 2005. As a graphic acknowledgement of the limited database upon which to express Estimated Average Requirements for water for different population groups, the Committee and the Institute of Medicine were forced to state "While it might appear useful to estimate an average requirement (an EAR) for water, an EAR based on data is not possible". Given the extreme variability in water needs that are not solely based on differences in metabolism, but also on environmental conditions and activities, there is not a single level of water intake that would assure adequate hydration and optimum health for half of all apparently healthy persons in all environmental conditions. Thus, an Adequate Intake (AI) is established in place of an EAR for water.

The AI for different population groups was set as the median water intake in populations from the National Health and Nutrition Examination Survey, whose intake levels varied greatly based on the survey years (e.g., NHANES 1988-94 vs NHANES 1999-2002) and also were much higher than the USDA surveys (e.g., 1989-91, 1994-98, or 2005-6). If the AI for adults as expressed in is taken as a recommended intake, we question the wisdom of the conversion of an AI into recommended water or fluid intake. The first problem is the almost certain inaccuracy of the fluid intake information from the national surveys, even though that problem may also exist for other nutrients. More importantly, from the standpoint of translating an AI into recommended fluid intake for individuals or populations, is the decision in setting the AI to add an additional roughly 20% of water intake, which is derived from some foods in addition to water and beverages. While this may be a legitimate effort to express total water intake as a basis for setting the AI, the recommendations that derive from this IOM report would better be directed at recommendations for water and other fluid intake on the assumption that the water content of foods would be a "passive" addition to total water intake. In this case, the observations of the DRI committee that water intake needs to meet needs imposed by not only metabolism and environmental conditions, but also body size, gender and physical activity. Those are the well studied factors which allow a rather precise measurement and determination of energy intake requirements. It is only logical that those same factors might underlie recommendations to meet water intake needs in the same populations and individuals, and therefore that consideration be given and data gathering be done by experimental and population research, to the possibility that water intake needs would best be expressed relative to the calorie requirements, as is done regularly in the clinical setting.

Table 5

Sex

Age

Kcals/d Estimated Energy Requirement

Al for fluid intake (ml/d)

Ratio AI ml/d: EER Kcal/d

It is important to note that only a few countries even include water on the list of nutrients. The European Food Safety Authority is developing a European wide standard. At present only the United States and Germany provide Adequate intake (AI) values but no other country does that.,

Another way of considering an approach to the estimation of water requirements beyond the limited usefulness of the AI or estimated mean intake is to express water intake requirements in relation to energy requirements in ml/kcal. An argument for this approach includes the observation that energy requirements are strongly evidence-based in each age and gender group on extensive research which takes into account body size, and activity level which are crucial determinants of energy expenditure which must be met by dietary energy intake. Such measures of expenditure have used highly accurate methods such as doubly-labeled water and thus EERs (Estimated Energy Requirements) have been set based on solid data rather than the compromise inherent in the AIs for water. Those same determinants of energy expenditure and recommended intake are also applicable to water utilization and balance and this provides an argument for pegging water/fluid intake recommendations to the better studied energy recommendations. The extent to which water intake and requirements are determined by energy intake and expenditure is understudied but in the clinical setting it has long been practice to supply 1 ml per kcal administered by tube to patients unable to take in food or fluids. Factors such as fever or other drivers of increased metabolism affect both energy expenditure and fluid loss and are thus linked in clinical practice. This concept may well deserve consideration in the setting of population intake goals.

Finally, for decades there has been discussion of expressing nutrient requirements per 1000 kcal so that a single number would apply reasonable across the spectrum of age groups. This idea, which has never been adopted by the Institute of Medicine (IOM) and National Academy of Science, may lend itself to an improved expression of water/fluid intake requirements which must replace the AIs eventually. presents the IOM water requirements and then develops a ratio of ml/kcal based on them. The European Food Safety Agency refers positively to the possibility of expressing water intake recommendations in ml/kcal as a function of energy requirements. Outliers in the adult male categories which reach ratios as high as 1.5 may well be based on American AI data which are above those in the more moderate and likely more accurate European recommendations.

Exploring the topic of utilizing ml/kcal as the way to examine water intake and water gaps, we take the full set of water intake AIs for each age-gender grouping and examine total intake in . They suggest a high level of fluid deficiency. Since a large proportion of fluids in the US are based on caloric beverages and this proportion has changed markedly over the past 30 years, fluid intake increases both the numerator and denominator of this ml/kcal relationship. Nevertheless even using 1 ml/kcal as the AI would leave a gap for all children and adolescents. We then utilize the NHANES physical activity data translated into METS/day to categorize all individuals by physical activity level and thus varying caloric requirements. Using these measures show a fairly large fluid gap, particularly for adult males as well as children.

Table 6

IV. DISCUSSION

This review has pointed out a number of issues related to water, hydration and health. As undoubtedly the most important nutrient and the only one whose absence will be lethal within days, understanding of water measurement and requirements are very important. The effects of water on daily performance and short and long-term health are quite clear. There are few negative effects of water intake and the evidence of positive effects is quite clear from the literature.

Little work has been done to measure total fluid intake systematically and there is no understanding of measurement error and best methods of understanding fluid intake. The most definitive US and European documents on total water requirements as based on these extant intake data., We feel that absence of validation of methods for water consumption intake levels and patterns represents a major gap. Little exploration of even varying methods of probing to collect better water recall data have been conducted.

Of course, the other half of the issue is the need for understanding total hydration status. We have no acceptable biomarkers of hydration status at the population level. Controversy exists about current knowledge of hydration status among older Americans., This represents a topic understudied at the population level though certainly scholars are focused on attempting to create biomarkers for measurement of hydration status.

As we have noted, the importance of understanding the role of fluid intake on health has emerged as a more important topic partially because of the shift toward large proportions of fluids coming from caloric beverages. We summarized briefly a related systematic review of the clinical, epidemiological and intervention literature on the effects of added water on health. As a replacement for SSB's, juice, or whole milk there are clear effects in that energy intake is reduced by about 10-13% of total energy intake. However on these topics, there are only a few longer-term systematic interventions and no published random-controlled longer-term trials. There is very minimal evidence on the effects of just adding water to the diet and of replacing water with diet beverages.

Limitations to this review are many. One certainly is the omission of discussions of the issue of potential differences in the metabolic functioning of different types of beverages. There is little basis at this point for delving into this sparse literature. Another is omission of the potential effects of fructose (from all caloric sweeteners) when consumed in caloric beverages on abdominal fat and subsequently all the metabolic conditions directly linked with this (e.g., diabetes). ⁻ We do not review in any detail all the array of biomarkers being considered to measure hydration status as there is just no sense in the field today that there is a measurement that covers more than a very short time period except for 24-hour total urine collection.

We suggest some ways to examine water requirements as a means to encouraging more dialogue on this important topic. Given the importance of water to our health and of caloric beverages to our total energy intake and potential risks of nutrition-related non communicable diseases, understanding both the requirements for water related to energy requirements, and the differential effects of water vs. other caloric beverages remain important outstanding issues.

In the end, this review has attempted to provide some sense of the importance of water to our health, its role in relationship to the rapid increases of obesity and other related diseases, and our gaps in understanding measurement and requirements. Water is essential to our survival and to our civilizations' and we hope this critical role will sharpen our focus on water in human health.

Acknowledgments

Funding was provided by the Nestlé Waters, Issy-les-Moulineaux, France, 5ROI AGI0436 from the National Institute on Aging Physical Frailty Program, and NIH R01- CA109831 and R01-CA121152. We also wish to thank Ms. Frances L. Dancy for administrative assistance, Mr. Tom Swasey for graphics support, Dr. Melissa Daniels for assistance, and Florence Constant (Nestle's Water Research) for advice and references.

Contributor Information

Barry M. Popkin, Department of Nutrition, University of North Carolina, Chapel Hill, NC.

Kristen E. D'Anci, Department of Psychology, Tufts University, Medford, MA.

Irwin H. Rosenberg, Nutrition and Neurocognition Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA.

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5. Scientific Opinion of the Panel on Dietetic Products Nutrition and Allergies. Draft Dietary reference values for water. The EFSA Journal. 2008:2-49.

11. Bar-David Y, Landau D, Bar-David Z, Pilpel D, Philip M. Urine osmolality among elementary schoolchildren living in a hot climate: implications for dehydration. Ambulatory Child Health. 1998;4:393-397.

12. Fadda R, Rapinett G, Grathwohl D, Parisi M, Fanari R, Schmitt J. International Society for Developmental Psychobiology; 2008. Washington, DC: 2008. The benefits of drinking supplementary water at school on cognitive performance in children.

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This review attempts to provide some sense of our current knowledge of water including overall patterns of intake and some factors linked with intake, the complex mechanisms behind water homeostasis, the effects of variation in water intake on health ...

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This articles is about the truth and false facts about water. True or false: Drinking extra water will keep your skin moist.

False. Although dry skin is a symptom of dehydration, once you are well hydrated, drinking more water will not make your skin dewier. Eating enough good-for-you fat from fish, nuts and healthy oils is more likely to help with that. These fats are essential building blocks for the healthy skin cell walls that keep moisture in and are key to a glowing complexion.

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It's now the norm to carry around a water bottle as if it's a permanent extension of your arm, so it seems that most of us have bought in to the benefits of proper hydration. But is what you think about your drink more hype than fact? Take this quiz to find out, and hydrate smarter throughout the hot summer days ahead.

True or false: Coffee and tea count toward hydration.

True. Even though caffeine is a diuretic, which forces water to be excreted in urine, our bodies quickly compensate. So even caffeinated beverages such as coffee and tea have a net hydrating effect. Sure, plain water and decaf beverages will hydrate you more, but you can still count that iced coffee as a quencher as much as it is an afternoon pick-me-up.

True or false: Coconut water hydrates better than water.

False. This one is firmly in the hype category. In 2012, a major coconut water player, Vita Coco, settled a class-action lawsuit that accused the company of misrepresenting the health benefits of its products, including exaggerated claims of being "super-hydrating." The company stopped marketing its products that way, but the claim is still rampant on the Internet. That's not to say that coconut water isn't hydrating - it is, just no more so than plain water.

True or false: Drinking extra water will keep your skin moist.

False. Although dry skin is a symptom of dehydration, once you are well hydrated, drinking more water will not make your skin dewier. Eating enough good-for-you fat from fish, nuts and healthy oils is more likely to help with that. These fats are essential building blocks for the healthy skin cell walls that keep moisture in and are key to a glowing complexion.

True or false: The foods you eat can help you stay hydrated.

True. Moisture in solid foods typically accounts for about 20 percent of our water intake, and you can up that number by digging into plenty of water-rich foods, which include many of the in-season fruits and vegetables this time of year. Think lettuce, summer squash, tomatoes, cucumber, melon, grapes, stone fruit and so on. Put them in smoothies with milk or include them in chilled soups.

True or false: Drinking water may help you lose weight.

True. Although it's no magic bullet, there is evidence that getting enough water can help with weight-loss efforts in several ways. For one, it can affect metabolism. When we are well hydrated, our cells burn more calories than if we are dehydrated - not a huge amount more, but every little bit helps. One study published in Obesity in 2008 found that women on a weight-loss plan who increased their water intake to more than one liter (about four cups) a day lost about five pounds more over the course of a year than those who drank less. Then there is the issue of satiety. Water-rich foods such as fruits, vegetables, soups and yogurt provide a high level of satisfaction, and there is some evidence that drinking water before a meal can help you eat less at that meal. Of course, drinking water instead of beverages such as soft drinks is also an easy way to cut calories.

True or false: A sports drink is necessary if you are running, playing soccer or (insert favorite activity here) in the heat.

False. If you are an athlete working out intensely for more than an hour at a time, raise your hand. If your hand is not up, you do not need a sports drink during or after exercising. The fluid and electrolytes you lose through sweat are easily, and more healthfully, replaced with water and a piece of fruit. If the taste of flavored beverages inspires you to drink, try adding a splash of juice or chunks of fruit to season your water.

True or false: You need to drink before you get thirsty.

False. In most healthy adults, thirst is a reliable indicator of fluid needs - and a critical one, as how much you need to drink can vary widely depending on how active you are and how hot it is outside. Unless you are doing prolonged exercise in the heat or your thirst mechanism is compromised (as it may be in the elderly or in those with medical conditions), you don't need to aggressively push fluids to stay ahead of thirst. Just pay attention to how you feel and drink plenty whenever you are thirsty, and you will most likely stay well hydrated.

True or false: You should aim to drink eight eight-ounce glasses of water a day.

False. That widely quoted number has no scientific basis whatsoever. The amount of water you need for optimal hydration depends on many variables, including the climate you live in and how active you are. The Dietary Reference Intakes from the National Academies of Sciences, Engineering and Medicine's Health and Medicine Division pinpoint 13 cups of total beverages for men and nine cups for women as the average adequate intake for proper hydration in temperate climates - emphasis on total beverages. That number assumes you are getting about 20 percent of your fluid from food, and it means that anything you drink counts toward hydration, including milk, juice, soft drinks and even coffee and tea. Those numbers are based on the average intakes of well-hydrated people, so you could need more or less. Let your thirst be your guide.

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It's now the norm to carry around a water bottle as if it's a permanent extension of your arm, so it seems that most of us have bought in to the benefits of proper hydration. But is what you think about your drink more hype than fact?

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Eggs are packed full of essential nutrients for growth including vitamin D, important B vitamins such as riboflavin and B12, and minerals such as iodine and selenium. There is good evidence that eggs can help to keep you feeling fuller for longer too.

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Surrey nutritionist creates six recipes that cost £1 or less per head

US research finds eggs is more filling breakfast than cereal or porridge

Poached egg on avocado bagel costs 63p a head and takes 10 mins

Make scrambled eggs in a mug for 91p a serving in under 12 mins

It's often called the most important meal of the day, but so many of us just skip breakfast altogether.

But now a nutritionist has created six speedy egg recipes that take less than 12 minutes to make - and even better, they all cost about £1 or less per head.

Dr Juliet Gray created the recipes for parents short on cash and time as the kids go back to school after research from the US found that eggs provide a more filling breakfast for children than cereal or porridge.

Scroll down for recipes

Her healthy breakfasts include egg in a mug at 42p a serving, and poached egg on an avocado bagel for 63p a head.

She came up with the idea after a study released in January of 40 children, aged 8-10 was conducted by the University of Pennsylvania.

It found that children who ate eggs for breakfast ate less at lunchtime compared with those who ate a meal based on either breakfast cereal or oatmeal (porridge

The Surrey nutritionist said: 'Eggs are packed full of essential nutrients for growth including vitamin D, important B vitamins such as riboflavin and B12, and minerals such as iodine and selenium. There is good evidence that eggs can help to keep you feeling fuller for longer too.'

Here, she shares the six recipes for you to try.

EGG IN A HOLE WITH TOMATO AND FETA

Swap traditional eggs on toast for 279-calorie eggs in a hole at 91p a serving - a runny fried egg served in the centre of wholemeal bread, topped with tomato, red peppers, cucumber and feta.

Save time in the morning and prep the salad the night before. Store in a bowl in the fridge until ready to use.

This is breakfast at the touch of a button with this colourful 332-calorie eggy scramble with peas, sweetcorn and cherry tomatoes served with brown pitta bread at 42p a head.

For a portable breakfast, split the pitta pocket and scoop in the egg.

An 'on the go' 335-calorie feast of wholemeal wrap packed with egg, red peppers, cucumber and spinach for 59p a serving.

Ideal for kids to eat on the way to school, boil the eggs the night before so they're all ready to slice in the morning.

MIXED BERRY FAIRY TOAST

Add a hint of magic to your child's breakfast with delicious honey and egg soaked wholemeal bread topped with berries and creamy Greek yogurt.

This version of French toast is only 261 calories for two and costs just 56p a serving.

PEA, HAM AND TOMATO OMELETTE

It's hard to go wrong with a classic omelette, filled with ham and veggies to help your family get their five-a-day.

It's 445 calories but full of protein to make you last until lunchtime, and costs just £1.08 a serving.

POACHED EGG ON AVOCADO BAGEL

A classic combination of smashed avocado with a tasty poached egg, all on top of a crunchy seeded bagel.

It costs just 63p a serving and has 271 calories.

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How to cook six healthy egg-based breakfasts for under £5

# data[].attributes.attachment_link.description
Surrey nutritionist creates six recipes that cost £1 or less per head US research finds eggs is more filling breakfast than cereal or porridge Poached egg on avocado bagel costs 63p a head and takes 10 mins Make scrambled eggs in a mug for 91p a serving in under 12 mins It's often called the most important meal of the day, but so many of us just skip breakfast altogether.

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As children, we were all reminded to drink milk to grow strong bones or to eat bananas to prevent cramping up on the soccer field. What our parents did not tell us, however, was that a variety of important minerals are crucial to our wellbeing.

Minerals are elements created in the earth that humans and animals cannot produce within their bodies. Despite our inability to synthesize these substances, they are critical to our everyday bodily function. We should get most of the minerals we need from plant and animal food sources, but sometimes we just can't consume enough from our food. If one's body does not have enough of certain minerals for prolonged amounts of time, he or she can develop a deficiency that can cause health problems. Luckily, many minerals can be taken as supplements and promote health in several different ways. Here are five important minerals that shoppers may be deficient in and the potential effects on their health.

Calcium
Calcium is the most abundant mineral in the body. It is best known for its crucial role in the development of bones and teeth, where 99% of the body's calcium is found, but it also ensures that the heart, nerves, muscles and other systems work correctly. Calcium is so important to life, in fact, that the body will demineralize and reabsorb calcium from the skeleton to combat a calcium deficiency. Continuously low levels of calcium can prevent optimal bone mass in youth and can accelerate bone loss and osteoporosis with age (1, 2).

Maintaining healthy calcium levels not only provides general health benefits, but it also has shown promise in preventing and alleviating the symptoms of certain conditions. By consuming the recommended daily allowance (RDA) of 1,000-1,200 mg per day, individuals have a lesser chance of developing osteoporosis, a condition in which the bones weaken. Those suffering from osteoporosis have an increased chance of hip fracture, one of the most serious consequences of the bone disease. Almost one-third of individuals who sustain hip fractures are in nursing homes within the year, and one in four die within that time. Hypertension is another condition that scientists have studied extensively in connection to calcium. Research has found that systolic blood pressure decreased by 0.34 mmHg and diastolic by 0.15 mmHg for each 100 mg/day increase in calcium intake.

Healthy levels of calcium are also associated with lower rates of rickets, kidney stones, premenstrual syndrome symptoms and also shows promise against colorectal cancer (1, 2).
Calcium absorption can be hindered by age, metabolic conditions, and medications, as well as the heavy consumption of alcohol and cigarettes.

It is important for shoppers to understand that several nutrients are required for proper calcium absorption and usage in the body. Protein, vitamin D, vitamin K2 and magnesium all play important roles on this front. Moreover, high-sodium and phosphorus-rich foods increase the loss of calcium in the urine (2).

Iron
With 80% of the world's population not getting enough iron, iron deficiency is the most common nutritional disorder in the world (3-4). Iron is critical to the metabolism; 92% of the body's iron is found in hemoglobin, red blood cells that carry oxygenated blood from the lungs to all other organs. It is also involved in the production of adenosine triphosphate (ATP), the body's energy source, as well as a component of hundreds of proteins and enzymes, many of which protect cells against potentially dangerous reactive oxygen species (3-4).

Low iron levels can lead to anemia, the most common symptoms of which are weakness and fatigue due to cells' lack of oxygen. Deficiency also leads to increased lactic acid production, which contributes to decreased exercise capacity and athletic performance. Iron is also crucial to healthy immune function with responsibilities ranging from spreading T cells and creating reactive oxygen species to fight pathogens. In children, iron deficiency is linked to impaired cognitive development, low school performance, and behavioral issues, as well as lower attention, arousal, and even attention deficient-hyperactivity disorder (3-4).

Those at the highest risk of an iron deficiency are children six months to four years old, adolescents, pregnant women, vegetarians, those who exercise intensely, individuals who suffer from certain diseases or conditions, and anyone who chronically loses blood. The RDA for iron is 8 mg per day for all adults over 51 and men 19-50. However women in their child-bearing years should consume 18 mg per day. Because excess iron cannot be excreted by the body as other substances are, iron supplements should not be taken unless diagnosed as deficient (3-4).

When advising shoppers about which iron form to pick, look for those that are easy to absorb and will not cause digestive discomfort. Ferrous salts (sulfate, fumarate, gluconate, lactate, glycine, succinate, citrate and sulfate) are said to be more bioavailable than ferric salts (ferric ammonium citrate). Carbonyl iron, iron amino acid chelates and polysaccharide-iron forms may have fewer GI side effects. In addition, several liquid forms are on the market that are said to offer better absorption.

Magnesium
Magnesium is critical to the formation of hundreds of enzymes and is involved in several different bodily processes, including ATP formation, DNA and RNA synthesis, ion transport and cell signaling. Magnesium is also involved in building the structures of bone, cell membrane and chromosomes and helps regulate the levels of calcium, copper, potassium and other nutrients in the body. This mineral, 60% of which is found in the skeleton and another 27% in muscle, is involved in over 300 metabolic reactions (5-6).

Magnesium deficiency has been linked to certain medical conditions, but supplementation has shown promise in alleviating the symptoms of many of these conditions. Low magnesium levels have been shown to increase the risk of developing asthma, but when inhaled through a nebulizer, it can enhance the effects of asthma medicine. Some research has also found that magnesium can alleviate symptoms of hypertension. In a cohort of 28,349 women followed for 9.3 years, the risk of developing hypertension was 7% lower for those taking the highest amount of magnesium (434 mg) versus the lowest (256 mg) per day. Research studying the relationship between magnesium and type-2 diabetes also showed positive results, suggesting that raising one's magnesium intake by 100 mg a day can result in up to a 15% decrease in diabetes risk. This mineral is also key to supporting proper bone mineral density. In one large study conducted in Norway, one's level of magnesium intake was inversely correlated with hip fracture risk (5-6).

Symptoms of magnesium deficiency can include agitation and anxiety, sleep disorders, irritability, nausea and vomiting, abnormal heart rhythm, low blood pressure, muscle spasm and weakness and seizures (5-6).

Potassium
Potassium is the positively charged ion inside of cells, and all bodily functions depend on a specific balance of potassium concentration inside and outside of the cells. Sodium and magnesium are critical to keep proper levels of potassium in cells. Potassium levels are about 30 times more inside cells than outside them, while sodium levels are 10 times lower inside cells than outside them. The concentration differences between the two minerals create an electrochemical gradient called the membrane potential that is maintain by ion pumps. Because this balance is so crucial in nerve impulse transmission, muscle contraction, heart function and the function of all cells and systems of the body, 20-40% of an adult's resting energy expenditure goes to maintaining it (7-8).

Potassium supports bone health, but the greatest promise comes from studies about potassium's effect on high blood pressure, heart disease and stroke. In a study of over 43,000 men followed for eight years, those in the top fifth for potassium intake, consuming an average of 4,300 mg of potassium a day, were 62% less likely to have a stroke than those in the lowest fifth, taking an average of 2,400 mg per day (7-8).

The most common causes of hypokalemia are excessive loss of potassium, resulting from prolonged vomiting or diarrhea, kidney disease, metabolic absorption issues, anorexia, and congestive heart failure. Symptoms of a potassium deficiency are weakness, lack of energy, muscle cramps, intestinal paralysis and bloating, constipation, and abdominal pain, irregular heartbeat, and abnormal EKG. The RDA for adults over 19 is 4,700 mg a day, but as people get older, they run a higher risk of having too much potassium, as their kidneys become less efficient at eliminating excess (7-8).

Selenium
Although only found in the body in small amounts, selenium is an essential part of many amino acids and biological functions. Selenium acts primarily as an antioxidant, fighting damaging free radicals, but research continues to discover the metabolic capabilities of selenoproteins (selenium-dependent enzymes) (9-10).

Low levels of selenium have been linked to heart disease and worsening atherosclerosis which can lead to heart attack and a stroke. Selenium deficiency is also linked with a higher risk of cancer-related deaths and research has supported that selenium may lower the risk of prostate cancer specifically (though the supplement cannot be said to cure, treat or prevent disease). A meta-analysis of over 144,000 people found that increased selenium intake was associated with a 31% lower risk of developing cancer and a 40% lower chance of cancer-related death. The effect of selenium on the immune system is currently being studied as well. Research has shown that selenium ensures optimal function of B-cell antibodies and produces t-cell immunities. Trials have suggested that Selenium can prevent viral load progression and increase immune cell count in HIV/AIDS patients who show low selenium levels (9-10). Again, the supplement cannot be used to treat or prevent any disease.

The RDA for selenium is 55 micrograms per day, but one may have a deficiency if they excessively smoke or drink alcohol, take birth control pills, or have a disease that impairs nutrient absorption such as Crohn's. Prolonged selenium deficiency is linked to the development of fatal forms of cardiomyopathy (9-10).

Be sure to let shoppers know that mineral supplementation is a good option that should be discussed with physicians to promote general health. WF

References
1. University of Maryland Medical Center Complementary and Alternative Medicine Guide, "Calcium," http://umm.edu/health/medical/altmed/supplement/calcium, accessed May 20, 2016.
2. Oregon State University Micronutrient Information Center, "Calcium," http://lpi.oregonstate.edu/mic/minerals/calcium, accessed May 21, 2016.
3. University of Maryland Medical Center Complementary and Alternative Medicine Guide, "Iron," http://umm.edu/health/medical/altmed/supplement/iron, accessed May 20, 2016.
4. Oregon State University Micronutrient Information Center, "Iron," http://lpi.oregonstate.edu/mic/minerals/iron, accessed May 21, 2016.
5. University of Maryland Medical Center Complementary and Alternative Medicine Guide, "Magnesium," http://umm.edu/health/medical/altmed/supplement/magnesium, accessed May 20, 2016.
6. Oregon State University Micronutrient Information Center, "Magnesium," http://lpi.oregonstate.edu/mic/minerals/magnesium, accessed May 21, 2016.
7. University of Maryland Medical Center Complementary and Alternative Medicine Guide, "Potassium," http://umm.edu/health/medical/altmed/supplement/potassium, accessed May 20, 2016.
8. Oregon State University Micronutrient Information Center, "Potassium," http://lpi.oregonstate.edu/mic/minerals/potassium, accessed May 21, 2016.
9. University of Maryland Medical Center Complementary and Alternative Medicine Guide, "Selenium," http://umm.edu/health/medical/altmed/supplement/selenium, accessed May 20, 2016.
10. Oregon State University Micronutrient Information Center, "Selenium," http://lpi.oregonstate.edu/mic/minerals/selenium, accessed May 21, 2016.
Paige Lazar is a freelance writer based in Mendham, NJ. Published in WholeFoods Magazine September 2016

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Minerals for Health and Wellness | Whole Foods Magazine

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As children, we were all reminded to drink milk to grow strong bones or to eat bananas to prevent cramping up on the soccer field. What our parents did not tell us, however, was that a variety of important minerals are crucial to our wellbeing.

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We always hear about how important it is to eat a wide range of vitamins and minerals, but it's only until we're not getting enough do we truly realise the effects.

Feeling tired for no reason, having low energy, looking pale and always getting sick can all be signs of certain nutrient deficiencies. Not getting enough vitamins and minerals can have long-term impacts on our health, too.

"Eating a well balanced diet is essential to get all the vitamins and minerals our body needs to function effectively," dietitian Kaitlyn Bruschi told The Huffington Post Australia.

"These essential nutrients have a range of roles in the body -- everything from synthesising body tissues such as our bones and muscles, to transferring nerve signals throughout the body, as precursors for thousands of enzymes in the body, to removing or neutralising waste products from the body."

As not all vitamins and minerals are produced naturally in the body, dietitian and sports nutritionist Robbie Clark highlights the importance of getting them from whole foods.

"The body requires many different vitamins and minerals (micronutrients) that are crucial for growth, development and preventing chronic diseases," Clark told HuffPost Australia. "Not all are produced naturally in the body, so you have to get them from your diet.

"The amount of each nutrient you should consume depends on your age, stage of life, health (if you suffer a chronic health condition or not), pregnancy and breastfeeding, and the amount of physical activity you do and at what intensity and level."

If we don't eat enough vitamins and minerals, the potential risks of becoming, or being, nutrient deficient are far-reaching.

"Without these essential nutrients we can't grow or function properly," Bruschi said. "This is particularly important during the early years of life when we are developing rapidly. Deficiencies of nutrients during this period can be particularly detrimental."

According to Bruschi and Clark, nutrient deficiencies can manifest in a variety of ways, both physically and mentally.

We need to be eating a variety of foods daily to get everything our bodies need to keep us healthy and happy.

"When micronutrients are not consumed in adequate quantities, a variety of undesirable symptoms may develop," Clark told HuffPost Australia. "These can include problems with digestion, skin problems, stunted or defective bone growth, mood and mental health problems, and even dementia."

With many fad diets removing food groups such as grains (which provide B vitamins and iron), nutrient deficiencies are not a rare occurrence. The most accurate and safe way to check your nutrient levels is through your GP.

"A nutritional deficiency occurs when the body doesn't absorb the necessary amount of a nutrient," Clark explained. "It may also occur in people who are fussy eaters and don't have a lot of variety in their food choices, or in people who avoid certain food groups, whether it be for personal reasons or due to a specific health condition."

To ensure you're getting enough vitamins and minerals, Bruschi recommends eating a variety of foods daily and to not rely solely on nutrient supplements.

"Supplements are a great way to top up your nutrient intake if you are struggling with your diet or during periods where requirements are increased, such as pregnancy," Bruschi told HuffPost Australia.

"However, it is important to remember that this should be seen as a short-term solution and not an alternative to healthy eating.

"There is so much more in our food than just vitamins and minerals, which we are discovering every day. We need to be eating a variety of foods daily to get everything our bodies need to keep us healthy and happy."

According to Bruschi and Clark, these are some (but not all) of the common signs of nutrient deficiencies, and what we can eat more of to help.

Vitamin A

Vitamin A is involved in immune function, skin health, vision, reproduction and cellular communication.

Signs and symptoms of deficiency:

Foods high in vitamin A (beta-carotene):

Vitamin C

"Vitamin C is an antioxidant used to neutralise bad chemicals in the body," Bruschi said.

Unlike most animals, humans aren't able to synthesise vitamin C on our own, so it is essential to get it through diet.

Signs and symptoms of deficiency:

Dry skin

Coarse or splitting hair

Bleeding gums

Gingivitis

Poor wound healing

Poor immunity -- recurring colds and flu

Tooth loss

Anaemia

Nosebleeds

Bruising

Delayed wound healing

Muscle weakness

Fatigue

Foods high in vitamin C:

Vitamin D

Vitamin D plays a role in immune function and promotes bone growth. According to Bruschi, getting your daily dose of vitamin D is incredibly easy.

"Only about 10 minutes of sun exposure per day is enough to produce your daily vitamin D requirements," Bruschi said.

Signs and symptoms of deficiency:

Overweight or obese

Depression

Aching bones

Low bone mineral density

Osteoporosis -- porous and brittle bones

Osteomalacia -- softening of bone

Rickets (a severe bone-deforming disease) -- bowing of legs, bending of spine, toneless muscles

Muscle weakness

Low blood levels of vitamin D

Foods high in vitamin D:

Fatty fish -- tuna, mackerel, sardines, salmon and trout

Liver and other organ meats

Eggs (yolk)

Mushrooms (which have been exposed to sunlight)

Cheese

Fortified food products

Vitamin E

"Vitamin E is an antioxidant that protects the body's cells from damage, muscle weakness and neurological issues," Bruschi said.

Signs and symptoms of deficiency:

Eye problems such as retinopathy and cataracts

Skin problems such as acne, blisters, scar tissue, stretch marks

Mild anaemia

Fertility issues

Brain function abnormalities

Foods high in vitamin E:

Dark green leafy vegetables

Nuts and seeds

Avocado

Almonds

Shellfish

Plant-based vegetable oils

Broccoli

Kiwi fruit

Vitamin K

"Vitamin K helps with blood coagulation and prevents clotting issues," Bruschi said.

Signs and symptoms of deficiency:

Bruise easily

Bleed easily

Heavy menstrual periods

Blood in urine or stool

Osteoporosis

Low bone mineral density

Foods high in vitamin K:

Vitamin B12

This vitamin plays a key role in the normal functioning of the brain and nervous system, as well as the formation of red blood cells.

"Deficiencies typically present as anaemia but can also cause spinal cord degeneration and poor brain development," Bruschi explained.

Signs and symptoms of deficiency:

Foods high in vitamin B12:

Other B vitamins

Other B vitamins include B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6, B7 (biotin) and folate.

Signs and symptoms of deficiency:

Problems with vision

Fatigue

Adrenal insufficiency

Oedema (fluid retention)

Athlete's foot

Pale skin

Dandruff

"Due to its role in brain development and function, folate requirements jump substantially during pregnancy. Without sufficient folate, neural tube defects can occur in the baby," Bruschi told HuffPost Australia.

"In the general population deficiencies can present as anaemia due to problems with red blood cell production, or mental health or neurological issues."

Foods high in folate:

Leafy greens

Legumes

Whole grains -- oats, brown rice, rye, etc.

Oranges

Bananas

Fortified products such as cereals, fruit juices and most breads

Essential fatty acids (omega-3)

Omega-3 fatty acids play a crucial role in brain function, as well as normal growth and development.

Signs and symptoms of deficiency:

Foods high in omega-3:

Oily fish - sardines, mackerel, tuna, salmon, swordfish

Eggs (yolk)

Flaxseeds

Fish oil supplements

Chia seeds

Walnuts

Calcium

Your body needs calcium to keep your bones and teeth strong, and to support skeletal structure and function.

Signs and symptoms of deficiency:

Foods high in calcium:

Fish with edible bones e.g. anchovies, mackerel, sardines, salmon

Dairy products

Dark green leafy vegetables

Fortified soy products

Nuts and seeds

Broccoli

Almonds

Iron

Iron is required for the production of red blood cells and to optimise oxygen transfer throughout the body.

Signs and symptoms of deficiency:

Foods high in iron:

Magnesium

Magnesium helps to maintain normal nerve and muscle function, supports a healthy immune system and keeps bones strong.

Signs and symptoms of deficiency:

Foods high in magnesium:

Zinc

"Zinc deficiency can result in lethargy and mental health issues, reduced immune function, dermatitis and delayed wound healing, and delayed physical development and sexual maturation," Bruschi said.

Signs and symptoms of deficiency:

Foods high in zinc:

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Vitamin And Mineral Deficiency Signs And Symptoms

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We always hear about how important it is to eat a wide range of vitamins and minerals, but it's only until we're not getting enough do we truly realise the effects. Feeling tired for no reason, having low energy, looking pale and always getting sick can all be signs of certain nutrient deficiencies.

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American Headache Society revealed that screening for vitamin deficiencies may be the key to unlock a quieter, calmer brain. Those who suffered from frequent migraines were significantly more likely to have low levels of vitamin D, vitamin B2, folate, and co-enzyme Q10. Because each vitamin plays an integral role in producing energy in cells, researchers theorize that not getting enough needed vitamins could trigger a migraine, prompting the brain for help.

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Migraines symptoms strike like lightening in the heads of 38 million men, women, and children in America. The causes can be mysterious. But recent research presented at the 58th Annual Scientific Meeting of the American Headache Society revealed that screening for vitamin deficiencies may be the key to unlock a quieter, calmer brain.

Migraines can be debilitating. Every 10 seconds someone in the United States goes to the emergency room because of throbbing head pain, adding up to 1.2 million visits a day. When researchers tested 7,691 patients for vitamin deficiencies, they found those who suffered from frequent migraines were significantly more likely to have low levels of vitamin D, vitamin B2, folate, and co-enzyme Q10. Because each vitamin plays an integral role in producing energy in cells, researchers theorize that not getting enough needed vitamins could trigger a migraine, prompting the brain for help.

"Further studies are needed to elucidate whether vitamin supplementation is effective in migraine patients in general, and whether patients with mild deficiency are more likely to benefit from supplementation," said the study's lead author Dr. Suzanne Hagler, a research fellow at the Cincinnati Children's Hospital Medical Center, in a statement.
Migraine Overview | HealthGrove
Previously, a 2012 study linked magnesium deficiency to migraine. Those who suffer from migraines regularly have been found to have low levels of magnesium compared to those who don't experience any migraines or headaches at all. Since then, doctors have recommended combining magnesium with a multivitamin when migraine symptoms first appear. These new findings may add to the list of necessary vitamins.

It's difficult to consume all of the dietary vitamins necessary to keep their body running efficiently, which is why many people turn to vitamin supplements for help. However, it's best to try to weave in vitamin-rich food items in order to help stave off looming migraines.

According to The National Institutes of Health Office of Dietary Supplements, vitamin D helps the body absorb calcium and is plentiful in salmon, tuna, swordfish, and also cheese and eggs. But the best options to turn to are either milk or orange juice fortified with vitamin D.

When it comes to vitamin B2, soybeans, spinach, turkey, almonds, and yogurt are ideal foods to incorporate into the diet. Folate is also found in many dark green vegetables like broccoli and spinach, along with chickpeas, beans, and lentils. Co-enzyme Q10 can also be found in broccoli, dark leafy greens, but also nuts, fish, shellfish, pork, chicken, and beef. Lastly, for a boost of magnesium, eat almonds, sunflower and pumpkin seeds, bananas, cashews, and flaxseed, and drink milk.

To learn more about vitamins, turn to our cheat sheet to help guide you through safe supplementation. .

Source: Green A, Hagler SE, Obrien H, et al. Riboflavin, CoEnzyme Q10, Folate, and Vitamin D Deficiency in Pediatric, adolescent, and Young Adult Migraine Patients. 58th Annual Scientific Meeting of the American Headache Society. 2016.

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What Your Migraine Tells You About Your Diet

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Migraines symptoms strike like lightening in the heads of 38 million men, women, and children in America. The causes can be mysterious. But recent research presented at the 58th Annual Scientific Meeting of the American Headache Society revealed that screening for vitamin deficiencies may be the key to unlock a quieter, calmer brain.

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Some of the fastest processes in our body run their course in proteins activated by light. The protein rhodopsin sees to it that our eyes can rapidly take in their ever-changing surroundings. Free-electron X-ray lasers such ...

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Heavier people do not need more protein after a workout, however, those who have intense resistance workout need more protein.Researchers found that the amount of protein required to boost muscle growth response differed on the intensity of the exercises participants did. In order for nutritionists to recommend the correct amount of protein we first need to consider specific demands of the workout, regardless of athlete's’ size.

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It is commonly believed that people with more muscle are required to take in more protein. But, a new study by University of Sterling, Scotland, shows otherwise. According to the findings of the study, heavier people do not need more protein after a workout, however, those who have intense resistance workout need more protein.

For the study, researchers recruited 86 people. Of these, participants who weighed below 143 pounds were put in lower lean body mass group and those weighing 154 pounds or above were categorized as the higher lean body mass.

"In our study, participants completed a bout of whole-body resistance exercise, where earlier studies - on which protein recommendations are based - examined the response to leg-only exercise. This difference suggests the amount of muscle worked in a single session has a bigger impact on the amount of protein needed afterwards, than the amount of muscle in the body," Kevin Tipton, professor of sport, health and exercise science in the Faculty of Health Sciences and Sport, said in a statement released Monday.

Respondents in both the groups had to undergo two trials in which they were given protein after resistance exercise. In the first trial, the participants consumed 20 grams (0.70 ounce) of whey protein and in the second, they had 40 grams (1.41 ounce) of whey protein after exercise.

Researchers found that the amount of protein required to boost muscle growth response differed on the intensity of the exercises participants did. The study showed that consumption of 40 grams of protein after whole body routine was more effective at stimulating muscle growth than 20 grams. This was observed irrespective of the size of the participants.

"Until now the consensus among leading sports nutritionists, including the American College of Sports Medicine and the British Nutrition Foundation, is that weightlifters do not need more than around 25 grams of protein after exercise to maximally stimulate the muscle's ability to grow," Tipton said.

"In order for nutritionists to recommend the correct amount of protein we first need to consider specific demands of the workout, regardless of athletes' size. This throws commonly held recommendations into question and suggests the amount of protein our muscles need after exercise may be dependent on the type of workout performed. These results are limited to younger, trained men so we may see different results with other groups, such as older individuals or females digesting different amounts of protein," Tipton added.

The study was published in peer-reviewed Physiological Reports

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Do People With More Muscle Need More Protein?

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It is commonly believed that people with more muscle are required to take in more protein. But, a new study by University of Sterling, Scotland, shows otherwise. According to the findings of the study, heavier people do not need more protein after a workout, however, those who have intense resistance workout need more protein.

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In 2013, when the world's tallest horse - a 20-hand, 2 3/4-inch tall (that's 6 feet, 11 inches) Belgian gelding named Big Jake - weighed in at 2,600 pounds, no one suggested that he should eat less than his daily 10 gallons of oats and a bale and a half of hay.

On the other hand, some dietary adjustments are needed to help the 2 billion people around the world who are overweight. But with all the debate about what constitutes a healthy diet (lately, headlines mistakenly screamed "Butter is back"), it's hard to know where to start.

Let's start with fat. Researchers have found that Americans' total fat consumption has skyrocketed from less than 45 pounds a year in 1950 to almost 75 pounds a year in 2000. That's 305,775 total calories per person per year. On top of that, a new study in Nature reveals that all that fat consumption tells your body to make more of a peptide called neurotensin (NT) - and NT's job is to boost fat absorption: Fat begets fat.

That's why you need to carefully choose your fats. Good fats can improve your health, reduce inflammation and insulin resistance and make your RealAge younger.

1. Eat skinless poultry and omega-3-rich fish like salmon and sea trout. Skip processed meats.

2. Avoid omega-6-loaded vegetable fats, like canola and soy oil, and stick with extra-virgin olive oil (except when high-heat cooking).

3. Enjoy healthy fats in nuts (walnuts are loaded with omega-3s) and avocados - just don't overdo it.

Mehmet Oz, M.D. is host of "The Dr. Oz Show," and Mike Roizen, M.D. is Chief Wellness Officer and Chair of Wellness Institute at Cleveland Clinic. To live your healthiest, tune into "The Dr. Oz Show" or visit www.sharecare.com.

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Get Healthy: Why too much bad fat makes you fatter

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In 2013, when the world's tallest horse - a 20-hand, 2 3/4-inch tall (that's 6 feet, 11 inches) Belgian gelding named Big Jake - weighed in at 2,600 pounds, no one suggested that he should eat less than his daily 10 gallons of oats and a bale and a half of hay.

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There are both “good” and “bad” fatty acids. “Good” fatty acids include unsaturated omega 3 fatty acids. They are considered good because they help reduce the risks of cardiovascular diseases and cognitive decline. Saturated and trans fatty acids are considered bad.

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Food, nutrition and human health institutes around the world have been fighting to reduce the risks associated with consuming detrimental fatty acids that are linked to cardiovascular diseases. But few people know what fatty acids are, which ones are harmful or beneficial, and how to identify them.

Fatty acids are a component of the fat found in foodstuffs such as meat, eggs, milk, vegetables, snacks, vegetable oils and most spreads. There are both "good" and "bad" fatty acids.

On average, fatty acids make up about 45% of people's daily calorie intake. This is much more than the recommended 20% to 35%.

Globally, the amount of fatty acids people consume is influenced by age, sex, country and region. Some reviews show that populations in Zimbabwe and Botswana consume too few "good" fatty acids. These make up less than 11% of their total daily energy intake.

Other studies have shown that young working-class adults in the developing world have high intakes of "bad" fatty acids - taking up more than 10% of their daily energy intake. This is similar to those in western countries.

The challenge is to improve dietary options so that fatty acid intakes are within the recommendations, which are set to help people reduce their risk of developing diet-related chronic diseases. These have been on the rise, especially in developing nations.

The reason for poor knowledge of fatty acids is simply due to not enough being done to improve awareness. For example, if fatty acids aren't labelled, consumers can't make informed decisions about the food they buy. In addition, a recent study around South Africa has shown that information is not the only deciding factor in the purchasing of foods. Cost also plays a role.

How customers make their choices

"Good" fatty acids include unsaturated omega 3 fatty acids. They are considered good because they help reduce the risks of cardiovascular diseases and cognitive decline. These are found in foods such as olive and flax seed oil, walnuts, seafood and fatty fish, such as salmon and tuna.

Saturated and trans fatty acids are considered bad. They have been clinically linked to increases in cholesterol levels and they increase the risk of several chronic diseases, such as type 2 diabetes, strokes, heart diseases and cancer. They emanate from increased dietary proportions of foods prepared using partially hydrogenated vegetable oil, dairy foods, fatty and processed meat cuts, and lard. The consumption of these foods is increasing significantly among resource-poor individuals, and fast-food and ready-to-eat-food consumers.

To gauge people's knowledge of fatty acids our study was conducted at grocery stores in the Eastern Cape province of South Africa. A great many of the food products, such as meat and vegetable oils, carried information about "good" fatty acids, including the fact that they contribute to a healthy heart and blood system.

Shoppers were asked if they trusted brand adverts that highlighted the perceived benefits of "good" fatty acids. Opinions varied among demographic groups.

In high-end neighbourhoods most participants knew the function and health benefits associated with omega 3. They used this knowledge to choose food products. But in poorer areas like townships and villages only a few people knew of omega 3 fatty acids. They admitted to using this kind of information rarely when deciding what products to buy.

All those interviewed had one thing in common: they attested to the importance of television adverts. It improved their knowledge of food products and influenced their decisions to select food products that contained "good" fatty acids, especially in high-end neighbourhoods.

But none of the participants had seen an advert from the country's national public health protecting agencies, such as the Public Health Association of South Africa. These bodies have the mandate to improve consumer awareness on health issues associated with fatty acids.

Although there is a strong inclination to promote "good" fatty acids, whose responsibility is it to explain the existence and dangers of "bad" saturated and trans fatty acids?

Protecting the public

In the US, the Food and Drug Administration has forced mandatory saturated fatty acids labelling on all packages to protect consumers.

Other developed nations, including those of the European Union, and Australia and Canada, have followed suit by promoting the voluntary reduction of "bad" fatty acids in food production.

But much remains to be done in sub-Saharan African states, where these fats have caused an unprecedented increase in cardiovascular diseases, which account for 11% of deaths on the continent.

There is no pressure on food producers to reduce fatty acids in food. In addition, there are limited regulations to force food producers or processors to label the type and amount of "bad" fatty acids on their products.

South Africa has a law that requires the labelling of trans fat in artificial "partially hydrogenated oils" and that it is kept at maximum of 2% of total energy. However, the maximum allowed fats are well higher than recommended levels (maximum 1%), exposing the consumer to health risks. There is very little public protection in other African countries.

In addition, consumers aren't warned that cooking food in particular ways - such as deep frying - can change the fatty acid profile from "good" to "bad".

Drastic changes in the advertising and labelling of foods are needed to improve awareness of the effects of processing and handling on the fatty acid quality of both raw and ready-to-eat food.

The way forward

The global economic downturn has directly increased the risks of food insecurity and nutritional inadequacy by reducing the quantity, quality and food choices of poor and vulnerable groups. This is particularly true for people living in sub-Saharan African countries.

Economic pressures have led to people shifting from traditional foods to cheaper and processed starchy, monotonous diets that are characterised by low micro-nutrient and high energy levels. In addition, foods prepared by re-used cooking oil have been reported in some establishments.

What this shows is that governments should prioritise the needs of poor consumers by running awareness campaigns about a safer fatty acid balance in their diets.

Food literacy campaigns are also important. These would help consumers understand more about fat and fatty acids.

The challenge is to improve nutrition and safety standards, while not destabilising access to food, through harsh penalties or obsessive labelling laws. The point is to reach a compromise that allows the consumer to make better and better-informed decisions.
Voster Muchenje This article was originally published on Read more: Don't replace saturated fats with processed carbs Fat is good for you Saturated vs. unsaturated fats The Conversation. Read the original article. , Professor of Meat Science and the co-host of the NRF SARChI Chair in Meat Science, University of Fort Hare and Carlos Nantapo, PhD Student, Animal Sciences Department, University of Fort Hare

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Why it's so important to know good fats from bad

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Food, nutrition and human health institutes around the world have been fighting to reduce the risks associated with consuming detrimental fatty acids that are linked to cardiovascular diseases. But few people know what fatty acids are, which ones are harmful or beneficial, and how to identify them.

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These Carbohydrates May Drastically Increase Your Risk of Lung Cancer

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Scientists from the University of Texas found that people who eat high glycemic index foods had a 49% higher risk of developing lung cancer.

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This website is explaining that carbohydrates are going to be the main fuel and not fat in athletes. The main idea behind the low carb diet is simple: Get the body to burn fat, not carbs, to fuel a workout. This website explains what different athletes should do for their body.

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The sports world has been abuzz in recent years with the idea that athletes could improve their performance by following an ultra high-fat, low-carbohydrate diet.

Fans of this diet plan said it allows them to run, swim or bike endless miles without needing to refuel with sugary foods. Others, like mixed martial artist George St. Pierre, said they use a low-carb diet to drop 20 to 30 lbs. (9 to 14 kilograms) in a five-day span before weigh-ins, qualifying for lower weight classes in their bouts. (Doing this can lead to deadly dehydration and should never be attempted without medical supervision.)

But is a low-carb diet safe, and does it actually improve athletic performance?

Though safe, restricting carbohydrates won't help athletes hit their peak, especially in high-intensity activities like a marathon, said Asker Jeukendrup, the director of mysportscience. [ Dieters, Beware: 9 Myths That Can Make You Fat]

"If you're trying to run your best possible time, carbohydrate is going to be the main fuel and not fat," said Jeukendrup, who has done some of the pivotal studies on how macronutrients affect exercise performance. "That is a well-established fact."

However, a low-carb diet could work for those exercising at lower intensities, such as ultramarathoners who slowly jog hundreds of miles, Jeukendrup said. However, whether people prefer to gnaw on beef jerky or granola bars during an ultramarathon would likely be a matter of personal preference, he said. That preference likely doesn't point to any concrete performance advantage for those who rely on a fat-adapted diet, he said.

Proposed benefits of fat-adapted diets

The idea behind the low-carb or "fat-adapted" diet is simple: Get the body to burn fat, not carbs, to fuel a workout.

Typically, a fat-burning diet includes 65 percent of its calories from fat, less than 25 percent from carbs and the remainder from protein, according to a 2015 study in the journal Sports Medicine. Some of these diets restrict carbohydrate intake even further, to just 20 grams (or about 80 calories) a day (for a 2,000 calorie diet, this would be just 4 percent of calories from carbohydrates). At this level, the body switches to a metabolic state called ketosis, in which it burns fat as fuel. [ Infographic: How the Body Uses Energy]

Because the body has a nearly unlimited supply of fat stores, some people have argued that carb-limited diets can help runners avoid a phenomenon known as "hitting the wall," in which they can experience a sudden, intense feeling of fatigue during their races, Jeukendrup said.

Hitting the wall occurs because although the carbohydrates (called glycogen) stashed in liver and muscle can fuel high-intensity exertion, "your carbohydrate sources are very limited," Jeukendrup told Live Science. "And that amount is not quite enough to run a marathon."

Because of this, marathon runners need to refill their glycogen stores, often midrace.

They'll chug sports drinks, swallow candy bars, or eat special goos and gels while they're racing to keep their glycogen stores up, said Dr. David Ludwig, a professor of nutrition at Harvard University in Massachusetts and the author of "Always Hungry?: Conquer Cravings, Retrain Your Fat Cells and Lose Weight Permanently" (Grand Central Life & Style, 2016).

"Unfortunately, the fuel that many athletes rely on is processed, fast-acting carbohydrate: sugar," Ludwig said.

For elite athletes, those quick, sugary calories get burned off quickly, but people doing more average levels of exercise may "become dependent upon constant, frequent infusions of carbohydrate" to fuel their performance, Ludwig said.

As a result, "a garden-variety athlete could easily take in more calories than they burn off, just to keep themselves feeling adequately fueled, and that defeats a basic purpose of physical activity," Ludwig told Live Science. Others complain of gastrointestinal distress when eating all those carbs during a marathon, Ludwig said.

Processing carbs also requires insulin, the hormone that allows sugar in the bloodstream to pass into the cells as fuel. But insulin also promotes fat storage, he said.

Another reason athletes switch to low-carb diets is to lower their water weight, or the amount of water their body is holding on to.

Each molecule of stored glycogen binds to three water molecules, said Jordan Moon, the program director of sports and health sciences and sports management at American Public and American Military University, and chief science officer at the fitness-tracking website FitTrace.com.

Some mixed martial artists and wrestlers, for example, will adopt a low-carb diet before weigh-ins to deplete their glycogen stores so they can drop water weight and qualify for a lower weight class, Moon said. Then, after the weigh-in but before the match, they'll switch to a high-carb diet, he said.

Do fat-adapted diets work?

But despite the hype, little evidence suggests that fat-adapted diets really improve athletic performance.

When the body doesn't have enough carbohydrates, it does increase its breakdown of fat, according to a 2015 study in the journal Metabolism Clinical and Experimental. In that study, ultra-endurance marathoners who were on an extremely low-carb diet could burn fat at twice the rate of those who were on a high-carb diet.

Still, low-carb, high-fat diets almost always lead to lower performance, according to more than a dozen studies conducted from 1960s to the 2000s. Because fat metabolism requires more chemical reactions in cells than metabolizing carbs does, it takes longer to produce the same amount of energy, meaning people who switch to burning fat can only exercise at a lower intensity compared to those who are burning carbs. [ Infographic: What Is VO2 Max?]

In some of the most definitive work on this subject, Louise Burke, an exercise physiologist at the Australian Institute of Sport, and her colleagues conducted a study of low-carbohydrate and high-carbohydrate diets for elite race walkers. Her work has found that low-carb diets reduced performance.

And cycling between a low- and high-carb diet, as many mixed martial artists may do, probably doesn't help performance either, said Melinda Manore, a biologist and nutrition scientist at Oregon State University who studies how exercise affects nutritional needs.

That's because going on a low-carb diet changes how many enzymes the body makes to burn carbohydrates, and it can take several days to reverse this. On the day of a fight, for instance, people on a low-carb diet won't be able to utilize their glycogen stores as well to perform at high intensity, she said.

Fat-adapted diets may work OK for some ultramarathoners or extreme endurance athletes who need to work out at low intensity for long periods of time. However, studies also suggest that people on high-carb diets can get excellent results in similar endurance challenges, Jeukendrup said.

Beyond that, low-carb diets are often difficult to follow. Consuming no carbs means no fruits, veggies or whole grains, Manore said. One of the competitive race walkers in Burke's study took to eating sticks of butter, according to a recent interview.

"Most athletes hate it. They can't stay on it. They don't feel good," Manore said. "It's just not practical."
Editor's Note: This story was edited to update Asker Jeukendrup's affiliation. He is no longer with the Gatorade Sports Science Institute.
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BEFORE YOU GO

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The sports world has been abuzz in recent years with the idea that athletes could improve their performance by following an ultra high-fat, low-carbohydrate diet. Fans of this diet plan said it allows them to run, swim or bike endless miles without needing to refuel with sugary foods.

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