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Scientific Reports 6, Article number: 18803 (2016)

doi:10.1038/srep18803

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Abstract

By importing food and agricultural goods, countries cope with the heterogeneous global water distribution and often rely on water resources available abroad. The virtual displacement of the water used to produce such goods (known as virtual water) connects together, in a global water system, all countries participating to the international trade network. Local food-production crises, having social, economic or environmental origin, propagate in this network, modifying the virtual water trade and perturbing local and global food availability, quantified in terms of virtual water. We analyze here the possible effects of local crises by developing a new propagation model, parsimonious but grounded on data-based and statistically-verified assumptions, whose effectiveness is proved on the Argentinean crisis in 2008-09. The model serves as the basis to propose indicators of crisis impact and country vulnerability to external food-production crises, which highlight that countries with largest water resources have the highest impact on the international trade, and that not only water-scarce but also wealthy and globalized countries are among the most vulnerable to external crises. The temporal analysis reveals that global average vulnerability has increased over time and that stronger effects of crises are now found in countries with low food (and water) availability.

Introduction

The international trade of agricultural goods causes a virtual displacement of the water used to produce such goods, "embedded" in trade as a factor of production1,2. The volume of freshwater (rainfall, surface water and groundwater) used for the production of such goods, and no more available for other uses at the production site, is known as virtual water (VW). Volumes can be summed across all different commodities and represent an alternative quantity to money or calories to investigate different aspects of the international trade. Agricultural commodities are by far, the most water-intensive traded products3 and they are in large part ultimately devoted to human consumption. Virtual water thus provides a quantitative general framework for the investigation of the water-food-trade nexus, posing the emphasis on water resources and the environment4.

Virtual water exchanged between producing and consuming countries defines flows across an international network associated to the commodity trade. This virtual water trade has relevant environmental and socio-economic implications, the most important one being that water-scarce countries can rely on water resources available abroad. In fact, in semi-arid countries, water scarcity limits the local agricultural production posing a key challenge to food security5. Importing food produced elsewhere enables such countries to overtake water resource limitations and to increase the food available to the population6, while possibly saving global water resources7,8. As a drawback, VW trade results in a marked country interdependency, and possibly in harsh inequalities when economic advantages, rather than environmental ones, drive the exchange of goods9,10.

In recent years, the international VW trade underwent marked modifications, following the expansion and evolution of commodity trade11,12,13. In the period 1996-2005, the average volume of virtual water exchanged worldwide was 2320 km ³ per year and represented about one fifth of the total volume embedded in consumed goods14. From 1986 to 2010, the traded VW volume grew more than twofold and the number of trade links had a widespread increase15, determining an evolution towards a globalized water system15,16,17. Given the increasing country interdependency, concerns have been raised about the sustainability of population growth under the constrain of limited global water resources18 and the potential reduction of societal resilience to crises19.

Globalization of commodity trade contributes to improve food availability and to sustain population by reducing the dependence on local resources20,21,22. In contrast, globalization favors the propagation of crises, as it leads to interconnected production-consumption systems that are complex and vulnerable to failures23. Models for the propagation of crises, or contagion, in networks have been developed in the context of complex systems, mostly basing on the random graphs theory24. By this approach, several studies about financial networks have addressed the risk associated to default events and how the spread of a crisis depends crucially on the pattern of interconnectedness between network nodes25,26,27. The structure of network interdependencies and feedbacks may also generate amplified responses to shocks, for example in input-output production networks28,29. However, the international trade network, of both food commodities and VW, is complex and its features and dynamics cannot be well described by random graphs30. Given the recognition that, also in international trade, network topology plays a key role in the spreading of economic crises31, specific models of shock propagation and vulnerability measures need to be developed for the (VW) trade network32,33.

A different approach to the analysis of trade dynamics, with specific reference to its effects on water endowments, is represented by agro-economic models, such as GTAP-W34 or IMPACT35. These models are based on the general equilibrium theory and mimic the dynamics of trade and associated use of water resources by also considering market mechanisms and price variability. Models based on the general equilibrium theory typically lend themselves to scenario analyses, providing qualitative indications about the future behavior of the global water system; in contrast, their coarse spatial and sectorial resolution and large data requirements limits their use for the quantitative analysis of the propagation of local crises, which is the aim of the present paper.

Pursuing a different approach, we propose here an analysis of the effects of local food-production crises at the annual scale, which bases on a simple and novel mechanistic model. Building on data-based rules, statistically verified assumptions and very few parameters, the model mimics the propagation of crises taking advantage of the observed network structure and VW flows. The model is then tested on a real case to confirm the correctness of the propagation mechanism, and it is then applied to the assessment of countries' impact and vulnerability to local crises.

Modeling the effect of crises

A national annual virtual water balance, following from a food balance expressed in terms of virtual water equivalent, can be stated for each country, c, at any year, , as

where and are the virtual water volumes associated to the import and export of agricultural commodities of country c, respectively; is the virtual water embedded in the primary agricultural production (or water footprint of production), and is the remaining term for the balance closure (i.e., the water footprint of food supply and stock). The term represents the virtual water embedded in the annual internal availability of agricultural goods which includes food consumption, stock variation and other minor terms, such as waste. A decrease of may indicate a decreased consumption of agricultural goods or a reduction of their stocks, indifferently, as separating these components or mimicking stock dynamics goes beyond the scope of the present work.

A crisis is identified by a marked decrease of agricultural production, expressed in terms of equivalent virtual water volume. This reduction can be triggered by environmental, social or economic events such as droughts, floods, pests, conflicts or economic crises, disregarding the few cases in which the decrease in agricultural production is counterpoised by an increased use of water resources. When a country undergoes a local crisis, the VW embedded in its agricultural production is decreased by a fraction, β, of the initial water footprint of production. The VW loss induced by the crisis is partitioned into a reduction of internal availability and a reduction of export, according to the relative weight of the two terms in the country VW balance (1). The country-specific export weight, a, identifies the so-called export propensity of the country.

The reduction of export propagates to all direct trading partners proportionally to the initial VW flows towards each of them, and all trading partners find themselves with a reduced volume of VW in the balance. The rule of proportional propagation is strongly supported by data, as detailed in the Method section. The reduced volume is again partitioned between internal availability and export in each country and propagated towards their trading partners. Calculations proceed iteratively until a prescribed level of accuracy is reached. At the end of the simulation, the reduction in production occurred in the first country reflects into modified VW flows in the trade network and reductions of virtual water availability worldwide, with a geographic distribution that depends on the network structure (topology and node-to-node trade). The proposed propagation model is similar to the one developed by Lee et al. 31 for the macroeconomic trade network, but here we use country-specific behaviors and data-based export propensities.

The model bases on assumptions that are statistically validated on real data of VW embedded in food production and trade (see the Method section): in particular, we found that (i) a decrease of agricultural production in a country is associated to a decrease of export in the same country, (ii) a decrease of import is associated to a decrease of export, and (iii) a decrease of production does not generally imply an increase of import. There is no clear evidence, from our dataset, of compensatory mechanisms by which countries suffering a reduction of VW import from one partner increase the VW import from elsewhere (new or existing links), nor that occasional compensation is related to country wealth. The use of global rules and local coefficients represents a compromise which, although not considering some specific policies (e.g., modification of imports, activation of new trade links, substitution of commodities, role of commodity prices), allows one to mimic the core dynamics of crisis propagation. The use of annual data does not enable the investigation of sub-annual consequences of food-production crisis, but the propagation model could be adapted to different time scales if suitable data were available.

Results

Test case: the Argentinean crisis

In 2008-09 Argentina underwent a crisis which markedly affected its economy and agricultural production. Triggered by the international financial crisis and by the local political economy (e.g., taxation of agricultural exports36,37), which induced a major reduction of exports, a decreased agricultural production occurred, strengthened by a prolonged drought within the country38. The decrease of Argentinean exports replicated that of agricultural production (see Supplementary Material, Figure S1) as the VW volumes of export and production are highly correlated (correlation coefficient equal to 0.979). The overall decrease of VW embedded in agricultural production and export (from 2007 to 2009) amounted for both variables to 25.8%.

The two-year decrease, corresponding to a parameter value , is used to run the propagation model for the Argentinean case study, starting from the unperturbed VW trade network in 2007. The impact of the Argentinean crisis on the VW trade resulting from the model simulation is shown in Fig. 1a, mapping the variations of VW import induced in all countries by the crisis. This is compared, in Fig. 1b, to the difference observed from 2007 to 2009 (final year of the crisis) in the VW fluxes originated from Argentina. This choice allows us to isolate the effect of the Argentinean crisis from the manifold modifications of overall VW trade induced by other political-economic dynamics.

Figure 1: Effects of the crisis in Argentina in 2008.

( a) Variations of VW import of countries, as obtained from the model, and ( b) variations of VW imports from Argentina between 2007 and 2009 as from data; in both panels, positive variations indicate a decrease of VW import, measured in km ³ [maps created with Matlab ® R14 software, Mapping Toolbox v.2.0.3 ( http://uk.mathworks.com/products/mapping/)].

The model results compare very well with data. Most impacted countries are correctly identified by the model and are Brazil, China and Spain, where the VW fluxes have decreased by more than 2 km ³ (from 30 to 50% of initial VW fluxes). Marked impacts are also suffered by South Africa, India, Malaysia, France and Chile, with a real and modeled decrease of 1-2 km ³, again corresponding to 30-50% of initial VW fluxes. Also countries with intermediate and negligible variations of VW trade show a good matching with the model results. The marked decrease of import observed in Morocco and Algeria is likely due to the initial phase of the Arab Spring rather than to the Argentinean crisis39, and are thus overlooked by the model.

Propagation of crises

Having shown the capability of the proposed model to mimic real dynamics, we use it to infer the propagation of possible crises hitting four different countries: USA, Italy, Japan and South Africa. Crises are quantified by a decrease of 30% of the water footprint of agricultural production in 2011, , see the Method section), then propagated in the virtual water trade network depicted by the 2011 data. Results are illustrated in Fig. 2 and Table 1.

Figure 2

Effect of possible crises originated in the USA ( a), Italy ( b), Japan ( c), and South Africa ( d) in 2011 ( β = 0.3), quantified by the percentage variations of per capita VW availability in all other countries. Dark grey indicates stronger impacts and light grey smaller impacts; red color identifies countries where the crises originated from [maps created with Matlab ® software, Mapping Toolbox v.2.0.3 ( http://uk.mathworks.com/products/mapping/)].

Table 1: Numerical details on the crises shown in Fig. 2: entity of the crisis, characteristics of the hit node and variations measured in the major trading partner (ΔI: variation of VW import, ΔA pc: variation of per-capita internal availability, ΔA r: percentage variation of per-capita internal availability).

The most impacted country in these crises is not necessarily the one receiving the largest share of export from the hit country. In fact, the model mimics the cascade dynamics on the network and reproduces the superimposition of disturbances reaching a country directly and indirectly, through different trade connections. This leads, for example, to the case of Japan, whose major trading partner in 2011 was Hong Kong, but the country modeled as having the overall largest reduction of import is China (−24 Mm ³ of VW); the same also occurs to possible crises hitting some large exporting countries, such as France and Indonesia, as well as minor countries (crises not shown).

The geographic extension of the four possible crises and the strength of impacts in all countries, measured by the percentage variation (decrease) of the per-capita VW internal availability are highlighted in Fig. 2. Variations of per-capita VW availability are small (see Table 1) because traded goods represent only a fraction of global agricultural production and because the crisis is spread within the network, distributing its effects on several countries. Having small variations is also coherent with the fact of considering a fixed network structure during crises propagation and only modeling fluxes variations; crises disrupting the trade network are not considered in this modeling framework.

Marked differences in the results are due to the different hit strengths, in that greater VW losses occur in hit countries with greater agricultural production; however, the spreading of the crisis depends on the (weighted) network of country connections and the characteristics of the hit node. In fact, although Italy and South Africa undergo a similar VW loss, the resulting picture of highly impacted countries (dark grey) is quite different and ranges from most part of Europe in the case of Italy, to only few African countries in the case of South Africa. Also the extension of the crisis propagation is different and affects (with a variation greater than 0.1%) 54 countries with 510 total million people in the case of Italy, and 21 countries with 292 total million people in the case of South Africa.

Comparing the four possible crises, the network-based differences among hit nodes should be taken into account. Hit-node characteristics can be described, for example, by the sum of incoming and outgoing links ( unweighted degree), by the sum of incoming and outgoing VW fluxes ( weighted degree), and by the eigenvector centrality, i.e. an influence score dependent on the links and fluxes of connected nodes40 (see Table 1). The large impact of the USA can be explained by its large degree and eigenvector centrality, and the small impact of Japan is anticipated by the limited connectivity and peripheral position of the country, given its very low eigenvector centrality. Italy shows a similar weighted degree to Japan but its higher unweighted degree and eigenvector centrality lead to a much different crisis propagation and a wider distribution among many (European) large partners. The case of South Africa differentiates from Italy in that effects of the crisis are concentrated into very few countries with marked variations, while other connections are poorly affected; this can be anticipated by the low eigenvector centrality (ratio of 1:4 with Italy) which indicates a small influence of the node in the weighted network.

Following these considerations, it can be argued that information on the network structure and weights are relevant to identify macro features, such as crisis entity and extension, but the country-specific distribution of impacts requires a model of crisis propagation, capable of describing the multiple effects of the propagating crisis. This is what our proposed model does.

Country impacts

The absolute impact of a crisis can be measured by the population-weighted average percentage reduction of VW availability induced in the network, i.e.

where is the variation of VW availability in country c, having population , due to the crisis in country x. Considering equivalent crises in all countries (same β), one can compare the different impacts of countries on the network, as shown in Fig. 3a.

Figure 3

Absolute ( a) and normalized ( b) impact of countries in 2011 ( β = 0.3), measured by the population-weighted average percentage reduction of VW availability induced in the rest of the world. White countries in panel ( a) have missing data in 2011 [maps created with Matlab ® R14 software, Mapping Toolbox v.2.0.3 ( http://uk.mathworks.com/products/mapping/)].

A strong correlation emerges between the absolute impact and the VW export fluxes of countries. In fact, large exporters of VW, such as the USA and Brazil have the largest impact on the network, European countries have an intermediate impact, while African and Middle Eastern countries have the smallest one. This correlation confirms the intuitive fact that crises with the largest impact are those hitting countries with larger VW fluxes towards the network. However, also the agricultural production of the hit country, P x, plays a role, in that VW volumes losses are defined as a fraction of it. To overcome such dependency on the crises entity and to highlight the role of the network, which is otherwise partially masked by the VW export of the hit country, a different indicator is required.

A normalized impact, , can thus be introduced, equal to the ratio between and the average percentage decrease of VW availability worldwide, evaluated as if the VW loss were uniformly distributed among the population, i.e.

This normalized impact does not depend on the parameter β and it is invariant with the entity of the crises, thus enabling a more even comparison among different crises and countries.

A unit value of indicates a crisis inducing variations of VW availability that are proportional to the existing VW availability of countries. On the contrary, values distant from the unit indicate the tendency of a crisis to generate modifications of VW availability that are more than (or less than) proportional to the existing VW availability of countries. Taking the VW availability as a proxy of the VW embedded in food consumption in a country (map in the Supplementary Material, Figure S2), the normalized impact can be considered a measure of "equity" of a country impact. In fact, (red colors in Fig. 3b) identifies countries whose crises have stronger effects on low-consuming countries and can be considered inequitable, while (green colors in Fig. 3b) identifies countries whose crises have stronger effects on high-consuming countries and are thus more equitable.

The joined analysis of absolute and normalized impacts in Fig. 3a,b allows us to make the following considerations. (i) Large American exporters, such as the USA, Canada, Brazil and Argentina, have a strong but equally distributed impact on the VW availability across the world. (ii) India, Thailand and Australia have a strong impact, which is mostly exerted on low-consuming countries; they are thus the most critical hotspots of the global water system. (iii) Intermediate-impact countries are usually unequal, with many of them affecting high-consuming countries (it is the case of major European countries, Russia, Ukraine, Mexico and Paraguay) and others affecting low-consuming countries (namely China, South Africa and Tanzania). (iv) Countries with low impact may show strong departure from the equal distribution of crises, however this is generally associated with small VW volumes traded and/or few trading partners, as can be seen, e.g., in Algeria or Zambia.

Country vulnerability

In the assessment of the effects of local crises on the virtual water trade network, a key feature is the vulnerability of countries. This feature expresses the country exposure to food-production crises occurring elsewhere and propagating in the global trade network. To this purpose, we introduce a measure of vulnerability for the c-th country, computed as the percentage reduction of VW internal availability in c resulting from a crisis occurred in x. The measure is then cumulated over all crises occurring in the other countries, hit one at a time, that is

The vulnerability measure depends on the overall import of a country, on the network characteristics of source nodes (e.g., their export propensity) and on the country reliance on internal agricultural production. International economic dynamics are not accounted for in our evaluation of country vulnerability whereas the focus lies in the country dependency on food (and VW) supply through the trade network.

Country vulnerabilities are shown in Fig. 4 (details in the Supplementary Table) and highlight marked heterogeneities. Most vulnerable countries are found in Europe and in the Middle East and North-African (MENA) countries. In central European countries, the condition of vulnerability is dictated by the intense trading within the EU market. This community of countries is almost fully connected and exchanged VW volumes are large; thus the whole system responds to the crises and critical situations emerge when the superimposition of effects is analyzed. Scandinavian countries, instead, have limited VW trade and their vulnerability originates in the limited agricultural production and consequently low self-sufficiency (water footprint of production lower than VW availability). Within Europe, lower vulnerabilities are found only in countries such as Spain, France, and Poland, having a large agricultural production and low VW net import, thus a greater self-sufficiency in terms of (virtual) water resources.

Figure 4: Vulnerability of countries in 2011 (β = 0.3), measured by the total percentage reduction of VW internal availability induced by all crises occurring in the rest of the world

In the MENA region, the large vulnerability is justified by the large VW import, a close second to Europe in per-capita terms41, and the limited VW export, although with a certain variability among countries. With large net import and low export propensity, most decreases of VW (thus food) volume directly impact the local availability rather than trading partners. This also happens to Japan and South Korea, which polarize such condition coupling large VW imports to negligible exports and forcing incoming crises to affect local VW availability. However, while in the latter countries the internal agricultural production and food stocks may play a role in mitigating the shortages and enable a better management of foreign crises, in the MENA region, where agricultural production suffers from water shortage, such mitigation cannot be pursued if not at high environmental and economic costs.

Other cases of medium-to-large vulnerabilities can be explained by large VW net imports despite the abundant agricultural production (such as Mexico and Turkey), or by low agricultural productions (in Suriname, Congo, Mali, Botswana), or a mix of large imports and low internal production (in Chile, Perù, Venezuela, Iran). Malaysia is a peculiar case, in that it shows large agricultural production and negative VW net import, suggesting a low vulnerability; however, its intense trading with large VW exporters such as Indonesia, India and Thailand, induces a great exposure to the risk of their failure, which in turn increases the overall vulnerability of the country.

Worldwide, low vulnerabilities (green colors) are found (i) in countries having large agricultural productions (e.g., Brazil, Argentina, USA, South Asia and Australia), which are self-sufficient in terms of virtual water (and food) even when external crises reach the country through trade, and (ii) in countries having low VW imports (e.g., African countries), which are peripheral in the VW trade network and thus not much "exposed" to external crises propagating in the VW trade network.

Discussion

Quantitative metrics have been introduced to evaluate the impact and vulnerability of countries in the global water system, represented by the ensemble of national VW balances connected through the VW trade network42. We now present ( Fig. 5) a joined analysis of the two metrics, including information on countries's own water resources, measured by the total volume of actual renewable water resources, which summarizes the average annual flow of rivers and recharge of aquifers generated from endogenous precipitation and the incoming flow originating outside the country43.

Figure 5: Absolute impact versus vulnerability of countries in 2011.

Circle areas indicate country populations (in million people) and colors scale according to the total renewable water resources of countries (in km ³/year). Numerical details are available in the Supplementary Table.

In general, two key features emerge from Fig. 5: the large impact of water-rich countries (right part of the diagram), and the water scarcity of most vulnerable countries (top part of the diagram). Less populated countries have very small impact and highest vulnerability, suggesting a dependency on external resources, possibly due to lack of land or water. At the other extreme are the large producers of agricultural goods (USA, Brazil, India and Indonesia), having the highest impact and abundant freshwater resources but heterogeneous vulnerability, depending on their exposure to external crises through the VW import.

Central European countries have high impact and high vulnerability, due to their intense international trading. Agricultural production does not cover the internal VW demand, and these countries have to rely on foreign water resources, balancing trade openness and globalization with the exposure to external crises. Given that most of Europe is characterized by high agricultural efficiency, favorable climate and availability of freshwater resources, there is a potential for improving such condition. Pursuing an increase of agricultural production in these countries, although challenged by a sustainable land management (e.g., avoiding resource exploitation, loss of biodiversity/ecosystem services), would decrease the reliance on VW trade and lead to more affordable levels of vulnerability.

MENA countries are known to be markedly dependent on VW imports and, wherever local water resources are lacking, the vulnerability becomes very high (e.g., Saudi Arabia, Yemen, Algeria, Iraq). Egypt is one of the most vulnerable countries, due to its dependency of VW imports, but it also has non-negligible impact, thanks to its export of greenhouse and irrigated-agriculture products which, however, pose a marked pressure on its limited freshwater resources. In the case of MENA countries, vulnerability is dictated by water scarcity and can hardly be managed through agricultural policies and planning.

A high vulnerability is also found in Japan and South Korea, i.e., in countries dependent on the VW trade despite their water abundance, while at the other edge one finds Argentina, having a marked impact on the VW trade network, and a very low vulnerability although its water resources are not as abundant as for other large producers. The low vulnerability of Argentina is not disproved by the crisis in 2008 which, in fact, was not triggered by a decrease of food imports from other countries (see Supplementary Material, Figure S1); rather, it began with a decrease of Argentinean agricultural production, and subsequently spread into the trade network.

Among the countries with the largest impact on the global water system, critical situations emerge where crises are more likely. For example, countries having limited freshwater resources have a higher probability to undergo an environmental crisis or being negatively affected by a drought; among them, those having largest impact include ( Fig. 5) Argentina, Thailand, Australia, Malaysia and Ukraine. On a different note, interpreting the above diagram through the country wealth, in terms of per-capita gross domestic product ( Supplementary Material, Figure S3), it clearly emerges that richer countries are characterized by very high vulnerability to external crises. Moreover, if one considers less wealthy countries as having a higher propensity to socio-economic crises, it is important to highlight that India, Pakistan, Vietnam and Nigeria (to mention the largest ones) have low wealth but large impact on the VW trade network. In all these countries, the agricultural and water management as well as the political-economic efforts (local and international) should aim at preventing the occurrence and limiting the effects of crises, which might otherwise propagate affecting people and nations worldwide.

As a final remark, we analyze the water system globalization through the temporal evolution of world-scale indexes of impact and vulnerability, obtained as population-weighted averages ( Fig. 6). The trajectory highlights an increase of both normalized impact and vulnerability at the global scale. At the beginning of the study period, the global water system favored equitable crises , having stronger effects (i.e., more than proportional reductions of VW availability) on high-consuming countries. However, the system has changed in time, evolving towards a less equitable propagation of crises , which imposes larger reductions on low-consuming countries. This evolution can be explained by the increase of VW import of less wealthy countries, which also increases their exposure to external crises, leading to a potential harshening of the inequality within the global water system at the occurrence of crises.

Figure 6: Temporal evolution, from 1986 to 2011, of world-averaged population-weighted values of vulnerability and normalized impact.

The world-average vulnerability also shows a clear evolution. It has been rather stable in the first decade of the study period, followed by a marked increase, only minimally affected by the world economical crisis in 2008-09. Driven by countries facing a fast growth, in population and wealth, the increase of vulnerability follows from the intensification of virtual water trade and the increase of global interconnectedness. On a country basis ( Supplementary Figure S4) a decrease of vulnerability from 1986 to 2011 is observed in Brazil, Argentina and few other countries, while the dominant trend on the map is an increase, which is stronger in China and South-East of Asia, in the south of Africa, in Central America, in Turkey and Eastern Europe. The increase of vulnerability in the VW trade network, coupled to the decrease of equity in the effects of crises, confirms the complexity as well as the fragility of the global water system and calls for an increased attention on the problem of food-production crises.

Methods

Data

Data of virtual water trade are based on the commodity trade dataset of the Food and Agricultural Organization of the United Nations (Faostat)44. Detailed international trade matrices, , are available at the annual time scale from 1986 to 2011 and express the quantity of agricultural commodity i traded in year from country a to country b. Trade data are converted into virtual water flows by multiplying traded quantities by the crop virtual water content, , assuming that commodities are produced in the countries of origin of the flows. The total VW trade matrix, , is then obtained by summing across all commodities, i.e.

The considered crop virtual water content is the sum of green and blue water, i.e. rainfall and surface-/groundwater, contributing to crop evapotranspiration and data are provided by the global assessment of the Water Footprint Network45,46 as an average for the period 1996-2005. The centrality of such period with respect to our datasets grants the virtual water content to be reliable for our analysis, while variations due to interannual fluctuations are not accounted for.

Agricultural production data are available from the same Faostat database44 at the annual time scale for the period 1961-2011. Production data, , express the quantity of agricultural commodity i produced by country a in year ; data are then converted into virtual water volumes using the country-specific and commodity-specific virtual water content45,46, including green and blue water. The overall production, to be included in the virtual water balance (1), results from the sum across all primary commodities, m i, in order to avoid for double-counting of water volumes involved in secondary products47, i.e.

The Faostat database has also provided the population data for all countries over the period 1986-201144, while the total volume of actual renewable water resources are given by the Aquastat database maintained by the Land and Water division of FAO48. The per-capita gross domestic product (GDP) at current prices in US Dollars is obtained from the national accounts section of the United Nations49. All data are available upon request to the corresponding author.

The propagation model

The method bases on the virtual water balance of country c (Eq. (1)) where import, , and export, , can be expressed through the virtual water trade matrix, VWT, as

being the virtual water flow from country a to country b. Knowledge of the virtual water embedded in production and trade (see the Data section) and choice of a prescribed year of data, enable the establishment of initial virtual water balances in all countries. The VW internal availability in each country is derived from Equation (1) and countries having negative availability are discarded from the analysis, as well as inactive countries without trade, for the impossibility to run the model in such cases (the number of remaining countries is 200-210, depending on the year, and discarded population is less than 1/1000 of world population). The country-specific VW availabilities obtained averaging over the period 1996-2005 compare well with the consumption data provided by Hoekstra and Mekonnen14 from the same period. Per capita VW availability in 2011 are shown in the Supplementary Material (Figure S2).

The network perturbation is represented by a local crisis inducing a decrease of the VW used for agricultural production in country x, which can be caused by environmental or socio-economic events. The decrease of production is expressed as a fraction, β, of the initial production value and reads

where τ is an iterative index and identifies the unperturbed condition. β may vary from 0, identifying an absence of perturbation, to 1, identifying an interruption of the country agricultural production (see the following assessments).

The decreased production of agricultural commodities in country x, expressed in VW volume, will affect partly the national availability and partly the country exports. The partition between the two terms is chosen to be proportional to the relative weight of availability and export in the country, and the modified terms of the country VW balance read

Where Parameter quantifies the export propensity of each country and tunes the impact of the perturbation on the network varying within the range [0,1], where 0 identifies a disturbance completely absorbed by a decrease of national availability and 1 identifies a disturbance totally reflected into a reduction of exports, preserving the national internal availability. In the following, a data-based evaluation of such parameter is shown.

The reduction of export (Eq. (9)) is propagated towards all trading partners of country x proportionally to the existing flows towards each of these countries. Following Eq. (7), the VW trade from country x to all partners, k, thus becomes

All trading partners will find themselves with a reduced volume of VW in the balance, similarly to country x but due to a reduced import rather than a reduced production. The disturbance affecting each importing country is then

which, assuming that production does not change, will have to be partitioned between internal availability and export according to Eqs (9,10), where substitutes and substitutes . Export reduction is again propagated towards all trading partners and the procedure is repeated iteratively, reproducing the propagation occurring in the network as a result of the initial crisis in country x. The recursive expression of the VW balance terms for country c at the n-th iteration reads

Iterations are interrupted when results reach a prescribed precision, that is when all terms in the trade matrix change less than a fraction ε of the previous values, i.e.

where is the final iteration step and ε is here taken equal to . At the end of the simulation, the reduction of production occurred in country x reflects into a reduction of VW availability in all countries, satisfying the relation

with a geographic distribution of reductions that depends on the trade network. The total iteration time is assumed to be shorter than the temporal scale of data, which is annual, because simulations mimic the continuous adjustments of trade to meet the equilibrium conditions between demand and supply. It is worth noticing that all variations of agricultural production and trade are referred to overall VW volumes, without tracking the composition in terms of commodities.

Model assumptions and parameter calibration

The propagation model bases on some assumptions and calibrations which are here supported by specific statistical analyses. These analyses are based on the variations of VW import, , VW export, , and VW in agricultural production, , measured in subsequent years within the period 1986-2011 (1961-2011 when only P is considered) in all world countries with population greater than 1 million people.

Variations of export vs. production

The model assumes that a decrease of agricultural production in a country induces a decrease of export in the same country. Such hypothesis has been verified with a sign test considering the sample of and the corresponding (same country, same years) sample of values. The one-tail sign test confirms that when the production decreases (increases), that is , the median of is significantly lower (greater) than zero, with test p-value equal to . This supports the model assumption that a decrease of production is associated to a decrease of export.

Variations of export vs. import

Similarly, the model assumes that a decrease of import in a country is related, to different extents, to a decrease of export in the same country. The sign test is thus applied to the sample of values and the corresponding (same country, same years) values; the test confirms that when the import decreases (increases), that is , the median of is significantly lower (greater) than zero, with test p-value equal to . This supports the model assumption that a decrease of import is associated to a decrease of export.

Variations of import vs. production

Implicitly, the model assumes that a decrease of production induces a decrease of export, rather than an increase of import. A sign test is then applied to the sample of values and the corresponding (all countries, all years) values. Again applying the one-tail test, one finds that when the production decreases (increases), that is , the median of is not significantly lower (greater) than zero, with test p-value equal to 0.84. This supports the model assumption that a decrease of production is not generally associated to an increase of import.

Calibration of the parameter β

The β parameter represents the entity of a crisis and equals the percentage variation of the VW in agricultural production of the hit country. An empirical distribution function is built for the negative percentage variations of the VW production recorded in all countries and all years from 1961 to 2011 (time span of production data) to guarantee a better definition of the curve tail (see Fig. 7a). The parameter value, , used in the Result section represents a critical event with 2.3% of exceedance relative frequency among all recorded decreases, thus a rare but not unlikely crisis. Considering all years and countries without conditioning to decreases of production, such crisis has an exceedance relative frequency of 0.8% thus, on average, every year one country experiences a similar event, if i.i.d. events are considered.

Figure 7: Data-based model calibration

( a) Cumulative empirical distribution of percentage decreases of VW production in the period 1961-2011. ( b) Fitting of the partition of crises proportional to the relative fraction of VW export and availability (identified by the 1:1 line), with grey levels scaling with country population, and comparison with a least square linear fitting weighted by country population. ( c) Fitting of the propagation of crises towards trading partners proportionally to the existing VW fluxes (1:1 line) and comparison with a least square linear fitting.

Partition of the crisis within each country

Both a decrease of VW in agricultural production (in the country hit by the crisis) and of VW import (in all countries reached by the crisis propagation) determine a decrease of VW volume in the balance of the country (Eq. (1)). This decrease, measured generically with , needs to be partitioned between a variation of internal VW availability and a variation of country VW export, provided that , according to Eq. (1). The partition is expressed by the country-specific parameter α, or country propensity for export. The parameter is assumed to be proportional to the relative weight of availability and export before the crisis (Eqs (9,10)), i.e.,

Figure 7b shows the ratio of VW export variations over the summed decrease of internal availability and export (increases are left out) as a function of the country- and year-specific α values. Points are depicted with different grey levels according to the population of countries they refer to, to differentiate between large and small countries.

Points are rather scattered due to the variety of country conditions and behaviors. The 1:1 line represents the model assumption that the partition of crises within countries depends on their export propensity (Eqs (9,10)). Although a common pattern does not emerge in country behaviors, the proposed model fits reasonably well with most points and in particular with those corresponding to large countries. The least-square regression line, weighted by country populations (dashed red line in Fig. 7b), is found very close to the model line, supporting the model assumption.

It may also be noticed that several cases exist in which countries increase their exports despite a reduction of summed internal availability and export (negative vertical axis). In such cases, losses are compensated by the reduction of VW availability and likely by stocks alone, which are mainly devoted to compensate for variable/uncertain food availability.

Propagation of the crisis towards the partners

The model assumes that VW export variations of a country are propagated towards trading partners proportionally to the virtual water flows exchanged before the crisis. This has been assessed on a sample of cases identified by a decrease of country VW export larger than 10 km ³ from one year to the following, provided that such decrease represented at least 10% of the initial export. This identified 20 cases in 26 years. In each case, initial fluxes towards the trading partners were normalized by the total VW export and the variations of flux were normalized with respect to the total variation of export. These values are then plotted in Fig. 7c, where the model rule of proportionality is represented by a single line (red solid line) and it compares well with data (coefficient of determination, , equal to 0.501) and with the least-square linear regression fitted to data. The same analysis performed with a less restrictive threshold of export decrease (1 km ³) identifies 226 cases; the model fitting is still very good .

The propagation of an export decrease among trade partners has been investigated using also other variables than the initial VW export flux. Both direct and inverse relationships have been sought with destination-country per-capita GDP, total GDP and population; however, none of these variables explained globally or locally more than 10% of the variance of flux variations .

Indicators of impact and vulnerability

The proposed propagation model allows one to distribute an initial local perturbation to the whole network accounting for the network topology and virtual water flows. The procedure can be repeated applying the same initial perturbation to each of the N countries, obtaining a matrix of resulting internal availability in country c, , due to a perturbation in country x. Notice the addition of the apex x to identify the country hit by the crisis.

Some indicators are then useful to investigate the effects of local crises in the virtual water trade network. The absolute impact of a perturbation occurring in country x can be expressed through Eq. 2, where and , and it depends on the country VW exports and the VW volume losses induced by the crisis. The normalized impact divides by the uniform percentage variation of VW availability induced in the world by the crisis, excluding the country of origin (Eq. (3)). Such normalized impact, , is independent on the crisis entity and it takes identical values if -for example- crises are defined by a given variation of VW export, rather than the loss of a given fraction of agricultural production. This normalized impact highlights the role of the network in defining the effects of crises. This is because it differentiates crises according to the most/least affected countries, taking values close to (or different from the) unit if countries are affected proportionally (or not proportionally) to their VW internal availability. Both absolute impact and normalized impact values are quantified for all countries in the Supplementary Table.

Measures of impact characterize the countries of origin of the crises, thus their active role in the propagation, as opposed to the passive role with respect to crises originated elsewhere, described by the country vulnerability. Vulnerability can be measured by the average percentage reduction of VW internal availability induced in country c by the perturbations triggered in all other countries, (Eq. (4)). In this case no population weight is necessary, as the percentage reduction within the summation term are referred to the same country.

The world-average population-weighted formulation of the variables (normalized impact and vulnerability), in a given year, are

where is the world average value, are the country-specific values of the considered variable and is the country population. The sum is extended to all countries in the world, N, that are active in the considered year.

Additional Information

How to cite this article: Tamea, S. et al. Global effects of local food-production crises: a virtual water perspective. Sci. Rep. 6, 18803; doi: 10.1038/srep18803 (2016).

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De Fraiture, C. , Cai, X. , Amarasinghe, U. , Rosegrant, M. & Molden, D. Does international cereal trade save water? The impact of virtual water tarde on global water use. Tech. Rep. Comprehensive Assessment Research Report n. 4, Int. Water Manag. Inst., Colombo (2004).

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Falkenmark, M. & Rockström, J. Balancing water for humans and nature: the new approach in Ecohydrology (Earthscan, London, UK, 2004).

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Bollobás, B. Random graphs (Cambridge University Press, Cambridge, UK, 2001). 2nd Edition.

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Fagiolo, G. & Alatriste Contreras, M. Propagation of economic shocks in Input-Output networks: a cross-country analysis (2014). ArXiv: 1401.4704v2.

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Download references

Acknowledgements

The authors acknowledge funding from the Italian Ministry of Education, University and Research (MIUR) through the project "The global virtual-water network: social, economic, and environmental implications" (FIRB - RBFR12BA3Y).

Author information

Affiliations

Politecnico di Torino, Department of Environment, Land and Infrastructure Engineering, Turin, 10129, Italy

Stefania Tamea

, Francesco Laio

& Luca Ridolfi

Authors

1. Search for Stefania Tamea in:

2. Search for Francesco Laio in:

3. Search for Luca Ridolfi in:

Contributions

All authors contributed to the work: F.L. and L.R. conceived the research, S.T. conducted the analysis and drafted the manuscript. All authors discussed the results at all stages and refined the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Stefania Tamea.

Supplementary information

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Global effects of local food-production crises: a virtual water perspective

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Altmetric: 28 More detail Article | Open Scientific Reports 6, Article number: 18803 (2016) doi:10.1038/srep18803 Download Citation Received: Accepted: Published: By importing food and agricultural goods, countries cope with the heterogeneous global water distribution and often rely on water resources available abroad.

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Vitamins & Minerals: Are You Getting What You Need?

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It's important to get enough vitamin and minerals in your diet, but you can have too much of a good thing. Learn the facts.

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Vitamin D, also known as the sunshine vitamin, is produced by the body as a response to sun exposure; it can also be consumed in food or supplements.

Having enough vitamin D is important for a number of reasons, including maintaining healthy bones and teeth; it may also protect against a range of conditions such as cancer, type 1 diabetes, and multiple sclerosis.

Vitamin D has multiple roles in the body, helping to:

Maintain the health of bones and teeth.

Support the health of the immune system, brain, and nervous system.

Regulate insulin levels and aid diabetes management.

Support lung function and cardiovascular health.

Influence the expression of genes involved in cancer development.

What is vitamin D?

Vitamin D is actually not a vitamin.

Despite the name, vitamin D is considered a pro-hormone and not actually a vitamin.

Vitamins are nutrients that cannot be created by the body and therefore must be taken in through our diet.

However, vitamin D can be synthesized by our body when sunlight hits our skin.

It is estimated that sensible sun exposure on bare skin for 5-10 minutes 2-3 times per week allows most people to produce sufficient vitamin D, but vitamin D breaks down quite quickly, meaning that stores can run low, especially in winter.

Recent studies have suggested that a substantial percentage of the global population is vitamin D deficient.

Health benefits of vitamin D

This section looks at the potential health benefits of vitamin D, from assisting good bone health to possible cancer prevention.

1) Vitamin D for healthy bones

Vitamin D is vital for bone health.

Vitamin D plays a substantial role in the regulation of calcium and maintenance of phosphorus levels in the blood, two factors that are extremely important for maintaining healthy bones.

We need vitamin D to absorb calcium in the intestines and to reclaim calcium that would otherwise be excreted through the kidneys.

Vitamin D deficiency in children can cause rickets, a disease characterized by a severely bow-legged appearance due to softening of the bones.

In adults, vitamin D deficiency manifests as osteomalacia (softening of the bones) or osteoporosis. Osteomalacia results in poor bone density and muscular weakness. Osteoporosis is the most common bone disease among post-menopausal women and older men.

2) Reduced risk of flu

Children given 1,200 International Units of vitamin D per day for 4 months during the winter reduced their risk of influenza A infection by over 40 percent.

3) Reduced risk of diabetes

Several observational studies have shown an inverse relationship between blood concentrations of vitamin D in the body and risk of type 2 diabetes. In people with type 2 diabetes, insufficient vitamin D levels may negatively effect insulin secretion and glucose tolerance. In one particular study, infants who received 2,000 International Units per day of vitamin D had an 88 percent lower risk of developing type 1 diabetes by the age of 32.

4) Healthy infants

Children with normal blood pressure who were given 2,000 International Units (IU) per day had significantly lower arterial wall stiffness after 16 weeks compared with children who were given only 400 IU per day.

Low vitamin D status has also been associated with a higher risk and severity of atopic childhood diseases and allergic diseases, including asthma, atopic dermatitis, and eczema. Vitamin D may enhance the anti-inflammatory effects of glucocorticoids, making it potentially useful as a supportive therapy for people with steroid-resistant asthma.

5) Healthy pregnancy

Pregnant women who are deficient in vitamin D seem to be at greater risk of developing preeclampsia and needing a cesarean section. Poor vitamin D status is associated with gestational diabetes mellitus and bacterial vaginosis in pregnant women. It is also important to note that high vitamin D levels during pregnancy were associated with an increased risk of food allergy in the child during the first 2 years of life.

6) Cancer prevention

Vitamin D is extremely important for regulating cell growth and for cell-to-cell communication. Some studies have suggested that calcitriol (the hormonally active form of vitamin D) can reduce cancer progression by slowing the growth and development of new blood vessels in cancerous tissue, increasing cancer cell death, and reducing cell proliferation and metastases. Vitamin D influences more than 200 human genes, which could be impaired when we do not have enough vitamin D.

Vitamin D deficiency has also been associated with an increased risk of cardiovascular disease, hypertension, multiple sclerosis, autism, Alzheimer's disease, rheumatoid arthritis, asthma severity, and swine flu, however more reliable studies are needed before these associations can be proven. Many of these benefits occur through Vitamin D's positive effect on the immune system

Recommended intake of vitamin D

The amount of vitamin D you need depends on your age.

Vitamin D intake can be measured in two ways: in micrograms (mcg) and International Units (IU).
One microgram of vitamin D is equal to 40 IU of vitamin D.
The recommended intakes of vitamin D throughout life were updated by the U.S. Institutes of Medicine (IOM) in 2010 and are currently set at:

Infants 0-12 months - 400 IU (10 mcg).

Children 1-18 years - 600 IU (15 mcg).

Adults to age 70 - 600 IU (15 mcg).

Adults over 70 - 800 IU (20 mcg).

Pregnant or lactating women - 600 IU (15 mcg).

Vitamin D deficiency

Although the body can create vitamin D, there are many reasons deficiency can occur. For instance, darker skin color and the use of sunscreen reduce the body's ability to absorb the ultraviolet radiation B (UVB) rays from the sun needed to produce vitamin D.

A sunscreen with sun protection factor (SPF) 30 can reduce the body's ability to synthesize the vitamin by 95 percent. To start vitamin D production, the skin has to be directly exposed to sunlight, not covered by clothing.

People who live in northern latitudes or areas of high pollution, work at night and stay home during the day, or are homebound should aim to consume extra vitamin D from food sources whenever possible. Infants who are exclusively breast-fed need a vitamin D supplement, especially if they are dark-skinned or have minimal sun exposure. The American Academy of Pediatrics recommends that all breastfed infants receive 400 IU per day of an oral vitamin D supplement; drops made specifically for babies are available.

Although vitamin D supplements can be taken, it is best to obtain any vitamin or mineral through natural sources wherever possible.

Symptoms of vitamin D deficiency

Symptoms of vitamin D deficiency may include:

Getting sick or infected more often.

Painful bones and back.

Depressed mood.

Impaired wound healing.

Muscle pain.

If Vitamin D deficiency continues for long periods of time it can result in:

Vitamin D deficiency may also contribute to the development of certain cancers, especially breast, prostate, and colon cancers. We explain this in a little more detail later.

Vitamin D food sources

Sunlight is the most common and efficient source of vitamin D. The richest food sources of vitamin D are fish oil and fatty fish. Here is a list of foods with good levels of vitamin D:

cod liver oil, 1 tablespoon: 1,360 IU

herring, fresh, raw, 4 ounces: 1,056 IU

swordfish, cooked, 4 ounces: 941 IU

raw maitake mushrooms, 1 cup: 786 IU

salmon, sockeye, cooked, 4 ounces: 596 IU

sardines, canned, 4 ounces: 336 IU

fortified skim milk, 1 cup: 120 IU

tuna, canned in water, drained, 3 ounces: 68 IU

egg, chicken, whole large: 44 IU

Potential health risks of consuming vitamin D

The Upper Level limit recommended for vitamin D is 4,000 IU per day. However, the National Institutes of Health (NIH) has suggested that vitamin D toxicity is unlikely at daily intakes below 10,000 IU per day.

Excessive consumption of vitamin D (hypervitaminosis D) can lead to over calcification of bones and hardening of blood vessels, kidney, lungs, and heart. The most common symptoms of hypervitaminosis D are headache and nausea but can also include loss of appetite, dry mouth, a metallic taste, vomiting, constipation, and diarrhea.

It is best to get your required Vitamin D from natural sources. When choosing supplements, choose your brand carefully as the FDA does not monitor safety or purity of supplements. If you want to buy Vitamin D supplements, then there is an excellent selection on online with thousands of customer reviews.

It is the total diet or overall eating pattern that is most important in disease prevention and achieving good health. It is better to eat a diet with a variety than to concentrate on one individual nutrient as the key to good health.

We picked linked items based on the quality of products, and list the pros and cons of each to help you determine which will work best for you. We partner with some of the companies that sell these products, which means Healthline UK and our partners may receive a portion of revenues if you make a purchase using a link(s) above.

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Debra Rose Wilson, PhD, MSN, RN, IBCLC, AHN-BC, CHT

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Vitamin D: Health benefits, facts, and research

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The body produces vitamin D in response to sun exposure. Vitamin D has a range of benefits. It protects the teeth and bones and defends against diseases, including cancer and multiple sclerosis. We look at how much vitamin D a person should have, where to find it, and how to recognize a deficiency.

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When it comes to dietary fat, what matters most is the type of fat you eat. Contrary to past dietary advice promoting low-fat diets, newer research shows that healthy fats are necessary and beneficial for health.

When food manufacturers reduce fat, they often replace it with carbohydrates from sugar, refined grains, or other starches. Our bodies digest these refined carbohydrates and starches very quickly, affecting blood sugar and insulin levels and possibly resulting in weight gain and disease. (1-3)

Findings from the Nurses' Health Study (4) and the Health Professionals Follow-up Study (5) show that no link between the overall percentage of calories from fat and any important health outcome, including cancer, heart disease, and weight gain.

Rather than adopting a low-fat diet, it's more important to focus on eating beneficial "good" fats and avoiding harmful "bad" fats. Fat is an important part of a healthy diet. Choose foods with "good" unsaturated fats, limit foods high in saturated fat, and avoid "bad" trans fat.

"Good" unsaturated fats - Monounsaturated and polyunsaturated fats - lower disease risk. Foods high in good fats include vegetable oils (such as olive, canola, sunflower, soy, and corn), nuts, seeds, and fish.

"Bad" fats - trans fats - increase disease risk, even when eaten in small quantities. Foods containing trans fats are primarily in processed foods made with trans fat from partially hydrogenated oil. Fortunately, trans fats have been eliminated from many of these foods.

Saturated fats, while not as harmful as trans fats, by comparison with unsaturated fats negatively impact health and are best consumed in moderation. Foods containing large amounts of saturated fat include red meat, butter, cheese, and ice cream. Some plant-based fats like coconut oil and palm oil are also rich in saturated fat.

When you cut back on foods like red meat and butter, replace them with fish, beans, nuts, and healthy oils instead of refined carbohydrates.

Read more about healthy fats in this "Ask the Expert" with HSPH's Dr. Walter Willett and Amy Myrdal Miller, M.S., R.D., formerly of The Culinary Institute of America

References

1. Siri-Tarino, P.W., et al., Saturated fatty acids and risk of coronary heart disease: modulation by replacement nutrients. Curr Atheroscler Rep, 2010. 12(6): p. 384-90.
2. Hu, F.B., Are refined carbohydrates worse than saturated fat? Am J Clin Nutr, 2010. 91(6): p. 1541-2. 3. Jakobsen, M.U., et al., Intake of carbohydrates compared with intake of saturated fatty acids and risk of myocardial infarction: importance of the glycemic index. Am J Clin Nutr, 2010. 91(6): p. 1764-8. 4. Hu, F.B., et al., Dietary fat intake and the risk of coronary heart disease in women. N Engl J Med, 1997. 337(21): p. 1491-9. 5. Ascherio, A., et al., Dietary fat and risk of coronary heart disease in men: cohort follow up study in the United States. BMJ, 1996. 313(7049): p. 84-90. 6. Hu, F.B., J.E. Manson, and W.C. Willett, Types of dietary fat and risk of coronary heart disease: a critical review. J Am Coll Nutr, 2001. 20(1): p. 5-19.
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When it comes to dietary fat, what matters most is the type of fat you eat. Contrary to past dietary advice promoting low-fat diets, newer research shows that healthy fats are necessary and benefic...

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Introduction

The protein requirements for athletic populations have been the subject of much scientific debate. Only recently has the notion that both strength/power and endurance athletes require a greater protein consumption than the general population become generally accepted. In addition, high protein diets have also become quite popular in the general population as part of many weight reduction programs. Despite the prevalence of high protein diets in athletic and sedentary populations, information available concerning the type of protein (e.g. animal or vegetable) to consume is limited. The purpose of this paper is to examine and analyze key factors responsible for making appropriate choices on the type of protein to consume in both athletic and general populations.

Role of Protein

Proteins are nitrogen-containing substances that are formed by amino acids. They serve as the major structural component of muscle and other tissues in the body. In addition, they are used to produce hormones, enzymes and hemoglobin. Proteins can also be used as energy; however, they are not the primary choice as an energy source. For proteins to be used by the body they need to be metabolized into their simplest form, amino acids. There have been 20 amino acids identified that are needed for human growth and metabolism. Twelve of these amino acids (eleven in children) are termed nonessential, meaning that they can be synthesized by our body and do not need to be consumed in the diet. The remaining amino acids cannot be synthesized in the body and are described as essential meaning that they need to be consumed in our diets. The absence of any of these amino acids will compromise the ability of tissue to grow, be repaired or be maintained.

Protein and Athletic Performance

The primary role of dietary proteins is for use in the various anabolic processes of the body. As a result, many athletes and coaches are under the belief that high intensity training creates a greater protein requirement. This stems from the notion that if more protein or amino acids were available to the exercising muscle it would enhance protein synthesis. Research has tended to support this hypothesis. Within four weeks of protein supplementation (3.3 versus 1.3 g·kg⁻¹·day⁻¹) in subjects' resistance training, significantly greater gains were seen in protein synthesis and body mass in the group of subjects with the greater protein intake (Fern et al., 1991). Similarly, Lemon et al. ( 1992) also reported a greater protein synthesis in novice resistance trained individuals with protein intakes of 2.62 versus 0.99 g·kg⁻¹·day⁻¹. In studies examining strength-trained individuals, higher protein intakes have generally been shown to have a positive effect on muscle protein synthesis and size gains (Lemon, 1995; Walberg et al., 1988). Tarnapolsky and colleagues ( 1992) have shown that for strength trained individuals to maintain a positive nitrogen balance they need to consume a protein intake equivalent to 1.8 g·kg⁻¹·day⁻¹. This is consistent with other studies showing that protein intakes between 1.4 - 2.4 g·kg⁻¹·day⁻¹ will maintain a positive nitrogen balance in resistance trained athletes (Lemon, 1995). As a result, recommendations for strength/power athletes' protein intake are generally suggested to be between 1.4 - 1.8 g·kg⁻¹·day⁻¹.

Similarly, to prevent significant losses in lean tissue endurance athletes also appear to require a greater protein consumption (Lemon, 1995). Although the goal for endurance athletes is not necessarily to maximize muscle size and strength, loss of lean tissue can have a significant detrimental effect on endurance performance. Therefore, these athletes need to maintain muscle mass to ensure adequate performance. Several studies have determined that protein intake for endurance athletes should be between 1.2 - 1.4 g·kg⁻¹·day⁻¹ to ensure a positive nitrogen balance (Freidman and Lemon, 1989; Lemon, 1995; Meredith et al., 1989; Tarnopolsky et al., 1988). Evidence is clear that athletes do benefit from increased protein intake. The focus then becomes on what type of protein to take.

Protein Assessment

The composition of various proteins may be so unique that their influence on physiological function in the human body could be quite different. The quality of a protein is vital when considering the nutritional benefits that it can provide. Determining the quality of a protein is determined by assessing its essential amino acid composition, digestibility and bioavailability of amino acids (FAO/WHO, 1990). There are several measurement scales and techniques that are used to evaluate the quality of protein.

Protein Sources

Protein is available in a variety of dietary sources. These include foods of animal and plant origins as well as the highly marketed sport supplement industry. In the following section proteins from both vegetable and animal sources, including whey, casein, and soy will be explored. Determining the effectiveness of a protein is accomplished by determining its quality and digestibility. Quality refers to the availability of amino acids that it supplies, and digestibility considers how the protein is best utilized. Typically, all dietary animal protein sources are considered to be complete proteins. That is, a protein that contains all of the essential amino acids. Proteins from vegetable sources are incomplete in that they are generally lacking one or two essential amino acids. Thus, someone who desires to get their protein from vegetable sources (i.e. vegetarian) will need to consume a variety of vegetables, fruits, grains, and legumes to ensure consumption of all essential amino acids. As such, individuals are able to achieve necessary protein requirements without consuming beef, poultry, or dairy. Protein digestibility ratings usually involve measuring how the body can efficiently utilize dietary sources of protein. Typically, vegetable protein sources do not score as high in ratings of biological value, net protein utilization, PDCAAS, and protein efficiency ratio as animal proteins.

Animal Protein

Proteins from animal sources (i.e. eggs, milk, meat, fish and poultry) provide the highest quality rating of food sources. This is primarily due to the 'completeness' of proteins from these sources. Although protein from these sources are also associated with high intakes of saturated fats and cholesterol, there have been a number of studies that have demonstrated positive benefits of animal proteins in various population groups (Campbell et al., 1999; Godfrey et al., 1996; Pannemans et al., 1998).

Protein from animal sources during late pregnancy is believed to have an important role in infants born with normal body weights. Godfrey et al. ( 1996) examined the nutrition behavior of more than 500 pregnant women to determine the effect of nutritional intake on placental and fetal growth. They reported that a low intake of protein from dairy and meat sources during late pregnancy was associated with low birth weights.

In addition to the benefits from total protein consumption, elderly subjects have also benefited from consuming animal sources of protein. Diets consisting of meat resulted in greater gains in lean body mass compared to subjects on a lactoovovegetarian diet (Campbell et al., 1999). High animal protein diets have also been shown to cause a significantly greater net protein synthesis than a high vegetable protein diet (Pannemans et al., 1998). This was suggested to be a function of reduced protein breakdown occurring during the high animal protein diet.

There have been a number of health concerns raised concerning the risks associated with protein emanating primarily from animal sources. Primarily, these health risks have focused on cardiovascular disease (due to the high saturated fat and cholesterol consumption), bone health (from bone resorption due to sulfur-containing amino acids associated with animal protein) and other physiological system disease that will be addressed in the section on high protein diets.

Vegetable Protein

Vegetable proteins, when combined to provide for all of the essential amino acids, provide an excellent source for protein considering that they will likely result in a reduction in the intake of saturated fat and cholesterol. Popular sources include legumes, nuts and soy. Aside from these products, vegetable protein can also be found in a fibrous form called textured vegetable protein (TVP). TVP is produced from soy flour in which proteins are isolated. TVP is mainly a meat alternative and functions as a meat analog in vegetarian hot dogs, hamburgers, chicken patties, etc. It is also a low-calorie and low-fat source of vegetable protein. Vegetable sources of protein also provide numerous other nutrients such as phytochemicals and fiber that are also highly regarded in the diet diet.

High Protein Diets

Increased protein intakes and supplementation have generally been focused on athletic populations. However, over the past few years high protein diets have become a method used by the general population to enhance weight reduction. The low-carbohydrate, high protein, high fat diet promoted by Atkins may be the most popular diet used today for weight loss in the United States (Johnston et al., 2004). The basis behind this diet is that protein is associated with feelings of satiety and voluntary reductions in caloric consumption (Araya et al., 2000; Eisenstein et al., 2002). A recent study has shown that the Atkins diet can produce greater weight reduction at 3 and 6 months than a low-fat, high carbohydrate diet based upon U.S. dietary guidelines (Foster et al., 2003). However, potential health concerns have arisen concerning the safety of high protein diets. In 2001, the American Heart Association published a statement on dietary protein and weight reduction and suggested that individuals following such a diet may be at potential risk for metabolic, cardiac, renal, bone and liver diseases (St. Jeor et al., 2001).

Protein Intake and Metabolic Disease Risk

One of the major concerns for individuals on high protein, low carbohydrate diets is the potential for the development of metabolic ketosis. As carbohydrate stores are reduced the body relies more upon fat as its primary energy source. The greater amount of free fatty acids that are utilized by the liver for energy will result in a greater production and release of ketone bodies in the circulation. This will increase the risk for metabolic acidosis and can potentially lead to a coma and death. A recent multi-site clinical study (Foster et al., 2003) examined the effects of low-carbohydrate, high protein diets and reported significant elevation in ketone bodies during the first three months of the study. However, as the study duration continued the percentage of subjects with positive urinary ketone concentrations became reduced, and by six months urinary ketones were not present in any of the subjects.

Comparisons between Different Protein Sources on Human Performance

Earlier discussions on protein supplementation and athletic performance have shown positive effects from proteins of various sources. However, only limited research is available on comparisons between various protein sources and changes in human performance. Recently, there have been a number of comparisons between bovine colostrum and whey protein. The primary reason for this comparison is the use by these investigators of whey protein as the placebo group in many of the studies examining bovine colostrum (Antonio et al., 2001; Brinkworth et al., 2004; Brinkworth and Buckley, 2002; Coombes et al., 2002; Hofman et al., 2002). The reason being that whey protein is similar in taste and texture as bovine colostrum protein.

Studies performed in non-elite athletes have been inconclusive concerning the benefits of bovine colostrum compared to whey protein. Several studies have demonstrated greater gains in lean body mass in individuals supplementing with bovine colostrum than whey, but no changes in endurance or strength performance (Antonio et al., 2001; Brinkworth et al., 2004). However, when performance was measured following prolonged exercise (time to complete 2.8 kJ·kg⁻¹ of work following a 2-hour ride) supplement dosages of 20 g·day⁻¹ and 60 g·day⁻¹ were shown to significantly improve time trial performance in competitive cyclists (Coombes et al., 2002). These results may be related to an improved buffering capacity following colostrum supplementation. Brinkworth and colleagues ( 2004) reported that although no performance changes were seen in rowing performance, the elite rowers that were studied did demonstrate an improved buffering capacity following 9-weeks of supplementation with 60 g·day⁻¹ of bovine colostrum when compared to supplementing with whey protein. The improved buffering capacity subsequent to colostrum supplementation may have also influenced the results reported by Hofman et al., ( 2002). In that study elite field hockey players supplemented with either 60 g·day⁻¹ of either colostrum or whey protein for 8-weeks. A significantly greater improvement was seen in repeated sprint performance in the group supplementing with colostrum compared to the group supplementing with whey protein. However, a recent study has suggested that the improved buffering system seen following colostrum supplementation is not related to an improved plasma buffering system, and that any improved buffering capacity occurs within the tissue (Brinkworth et al., 2004).

In a comparison between casein and whey protein supplementation, Boirie and colleagues ( 1997) showed that a 30-g feeding of casein versus whey had significantly different effects on postprandial protein gain. They showed that following whey protein ingestion the plasma appearance of amino acids is fast, high and transient. In contrast, casein is absorbed more slowly producing a much less dramatic rise in plasma amino acid concentrations. Whey protein ingestion stimulated protein synthesis by 68%, while casein ingestion stimulated protein synthesis by 31%. When the investigators compared postprandial leucine balance after 7-hours post ingestion, casein consumption resulted in a significantly higher leucine balance, whereas no change from baseline was seen 7-hours following whey consumption. These results suggest that whey protein stimulates a rapid synthesis of protein, but a large part of this protein is oxidized (used as fuel), while casein may result in a greater protein accretion over a longer duration of time. A subsequent study showed that repeated ingestions of whey protein (an equal amount of protein but consumed over a prolonged period of time [4 hours] compared to a single ingestion) produced a greater net leucine oxidation than either a single meal of casein or whey (Dangin et al., 2001). Interestingly, both casein and whey are complete proteins but their amino acid composition is different. Glutamine and leucine have important roles in muscle protein metabolism, yet casein contains 11.6 and 8.9 g of these amino acids, respectively while whey contains 21.9 and 11.1 g of these amino acids, respectively. Thus, the digestion rate of the protein may be more important than the amino acid composition of the protein.

In a study examining the effects of casein and whey on body composition and strength measures, 12 weeks of supplementation on overweight police officers showed significantly greater strength and lean tissue accruement in the subjects ingesting casein compared to whey (Demling and DeSanti, 2000). Protein supplementation provided a relative protein consumption of 1.5 g·kg·day⁻¹. Subjects supplemented twice per day approximately 8-10 hours apart.

Only one study known has compared colostrum, whey and casein supplementation (Fry et al., 2003). Following 12-weeks of supplementation the authors reported no significant differences in lean body mass, strength or power performances between the groups. However, the results of this study should be examined with care. The subjects were comprised of both males and females who were resistance training for recreational purposes. In addition, the subject number for each group ranged from 4-6 subjects per group. With a heterogeneous subject population and a low subject number, the statistical power of this study was quite low. However, the authors did analyze effect sizes to account for the low statistical power. This analysis though did not change any of the observations. Clearly, further research is needed in comparisons of various types of protein on performance improvements. However, it is likely that a combination of different proteins from various sources may provide optimal benefits for performance.

References

Boirie Y., Dangin M., Gachon P., Vasson M.P., Maubois J.L., Beaufrere B. (1997) Slow and fast dietary proteins differently modulate postprandial protein accretion. Proclamations of National Academy of Sciences 94, 14930-14935 [PMC free article]

Food and Agriculture Organization/World Health Organization (1990) Protein quality evaluation; report of the joint FAO/WHO expert consultation. FAO Food and Nutrition Paper 52, Rome, Italy

Fry A.C., Schilling B.K., Chiu L.Z.F., Weiss L.W., Kreider R.B., Rasmussen C.J. (2003) Muscle fiber and performance adaptations to resistance exercise with MyoVive, colostrum or casein and whey supplementation. Research in Sports Medicine 11, 109-127

Geiser M. (2003) The wonders of whey protein. NSCA's Performance Training Journal 2, 13-15

Godfrey K., Robinson S., Barker D.J.P., Osmond C., Cox V. (1996) Maternal nutrition in early and late pregnancy in relation to placental and fetal growth. British Medical Journal 312, 410-414 [PMC free article]

Navder K.P., Lieber C.S. (2003a) Nutritional support in chronic disease of the gastrointestinal tract and the liver. : Nutritional Aspects and Clinical Management of Chronic Disorders and Diseases. : Bronner F., editor. Boca Raton, FL: CRC Press; 45-68

Navder K.P., Lieber C.S. (2003b) Nutrition and alcoholism. : Nutritional Aspects and Clinical Management of Chronic Disorders and Diseases. : Bronner F., editor. Boca Raton, FL: CRC Press; 307-320

Potter S.M. (2000) Soy-new health benefits associated with an ancient food. Nutrition Today 35, 53-60

Tikkanen M.J., Wahala K., Ojala S., Vihma V., Adlecrerutz H. (1998) Effect of soybean phytoestrogen intake on low density lipoprotein oxidation resistance. Proclamations of the National Academy of Science 95, P3106-P3110 [PMC free article]

United States Dairy Export Council (1999) Reference Manual for U.S. Whey Products 2nd Edition

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The protein requirements for athletic populations have been the subject of much scientific debate. Only recently has the notion that both strength/power and endurance athletes require a greater protein consumption than the general population become generally accepted.

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Are all calories created equal? A new study suggests that in at least one important way, they may not be.

Sugary foods and drinks, white bread and other processed carbohydrates that are known to cause abrupt spikes and falls in blood sugar appear to stimulate parts of the brain involved in hunger, craving and reward, the new research shows. The findings, published in The American Journal of Clinical Nutrition, suggest that these so-called high-glycemic foods influence the brain in a way that might drive some people to overeat.

For those who are particularly susceptible to these effects, avoiding refined carbohydrates might reduce urges and potentially help control weight, said Dr. David Ludwig, the lead author of the study and the director of the New Balance Foundation Obesity Prevention Center at Boston Children's Hospital.

"This research suggests that based on their effects on brain metabolism, all calories are not alike," he said. "Not everybody who eats processed carbohydrates develops uncontrollable food cravings. But for the person who has been struggling with weight in our modern food environment and unable to control their cravings, limiting refined carbohydrate may be a logical first step."

Regardless of the diet they choose, most people who lose a great deal of weight have a difficult time keeping it off for good. For many people, despite their best efforts, the weight returns within six months to a year. But a few studies of weight loss maintenance, including a large one in The New England Journal of Medicine in 2010, have reported some success with diets that limit high-glycemic foods like bagels, white rice, juice and soda.

In addition to raising blood sugar, foods that are sugary and highly caloric elicit pronounced responses in distinct areas of the brain involved in reward. Earlier imaging studies have shown, for example, that the main reward and pleasure center, the nucleus accumbens, lights up more intensely for a slice of chocolate cake than for blander foods like vegetables, and the activation tends to be greater in the brains of obese people than it is in those who are lean.

But do rich desserts have a select ability to change our longer-term eating habits?

To get a better idea, Dr. Ludwig and his colleagues recruited a dozen obese men and then fed them milkshakes on two different occasions separated by several weeks. In each case, the milkshakes were nearly identical: flavored with milk and vanilla, and containing the same amount of calories, carbohydrates, protein and fat.

But on one occasion, the shakes were made with high-glycemic corn syrup; on the other, a source of low-glycemic carbohydrates was used. "These test meals were identical in appearance and tastiness, and we verified that our subjects had no preference for one or the other," Dr. Ludwig said.

As expected, blood sugar levels rose more quickly in response to the high-glycemic milkshake. But the researchers were especially interested in what happened several hours later, about the time most people are ready for their next meal.

What they found was that four hours after drinking the high-glycemic shake, blood sugar levels had plummeted into the hypoglycemic range, the subjects reported more hunger, and brain scans showed greater activation in parts of the brain that regulate cravings, reward and addictive behaviors. Although the subject pool was small, every subject showed the same response, and the differences in blood flow to these regions of the brain between the two conditions "was quite substantial," Dr. Ludwig said.

"Based on the strength and consistency of the response," he added, "the likelihood that this was due to chance was less than one in a thousand."

Previous research suggests that when blood sugar levels plummet, people have a tendency to seek out foods that can restore it quickly, and this may set up a cycle of overeating driven by high-glycemic foods, Dr. Ludwig said. "It makes sense that the brain would direct us to foods that would rescue blood sugar," he said. "That's a normal protective mechanism."

Christopher Gardner, a nutrition scientist at Stanford University who was not involved in the new study, said that after decades of research but little success in fighting obesity, "it has been disappointing that the message being communicated to the American public has been boiled down to 'eat less and exercise more.'"

"An underlying assumption of the 'eat less' portion of that message has been 'a calorie is a calorie,'" he said. But the new research "sheds light on the strong plausibility that it isn't just the amount of food we are eating, but also the type."

Dr. Gardner said it was clear that the conventional approach of the past few decades was not working. A more helpful message than "eat less," he said, may be "eat less refined carbohydrates and more whole foods."

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Are all calories created equal? A new study suggests that in at least one important way, they may not be. Sugary foods and drinks, white bread and other processed carbohydrates that are known to cause abrupt spikes and falls in blood sugar appear to stimulate parts of the brain involved in hunger, craving and reward, the new research shows.

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This article talks about how water shortage may affect the climate in which certain types of food grow in them. How scientists are already saying that a global climate change is already happen to us. How flooding and changing weather conditions can affect where food has been growing for years.

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Advertisement

The rich play with fire and the poor get burned. That sums up a report issued March 31 by the U.N. Intergovernmental Panel on Climate Change (IPCC) about the worsening risks of climate change. Yet even rich nations will face serious challenges. "Nobody on this planet is going to be untouched by climate change," said IPCC chair Rajendra Pachauri at a press conference releasing the report in Yokohama, Japan.

According to Pachauri and the hundreds of scientists who prepared the report, climate change is no longer something that will happen in the future. It is already here, and it is already impacting people on all seven continents and seven seas. The world now has a different climate than it had only a few decades ago, thanks to fossil fuel burning, forest clearing and other human activities.

As a result, the need for nations everywhere to adapt is already here, according to the report of the second team of IPCC scientists (known as Working Group II), who assessed more than 12,000 scientific papers to deliver an authoritative consensus on the impacts of climate change, the vulnerabilities of society and the natural world, as well as how we might adapt to a changed climate. "We see impacts from the equators to the poles and the coast to the mountains," noted biologist Christopher Field of Stanford University, co-chair of Working Group II at the press event.

The opportunity to prevent catastrophic global warming has not disappeared, even if the world has burned through half the fossil fuels it can, according to the first team of IPCC scientists who assessed the fundamental physics of climate change and released their report in September. But the world must drop its carbon habit soon. Since 1880, 531 gigatons of carbon have been emitted, and the IPCC scientists estimate that no more than 800 gigatons should be emitted for a better-than-even chance of keeping global warming below 2 degrees Celsius. If warming rises beyond that threshold, the scientists say, serious harm will be done to ecosystems and societies everywhere. The more warming, the greater the risk of " severe, pervasive and irreversible impacts," the new report states.

Unfortunately, in just the time between this report and the last iteration in 2007, climate change has grown 40 percent stronger thanks to ever increasing emissions of greenhouse gases. Already, the world has warmed 0.85 degree C since 1880. Global warming is now "unequivocal" and concentrations of CO2 have reached levels " unprecedented in at least the last 800,000 years." Or as Michel Jarraud, secretary-general of the World Meteorological Organzation put it at the press conference: "Ignorance is no longer an excuse. We know."

In that light, climate change becomes a risk management proposition, particularly given the uncertainty about exactly how bad impacts might become and when. The worst risks include sea level rise for small islands and coasts, flooding, the breakdown of infrastructure in the face of extreme weather, loss of livelihoods for farmers and fishers, food insecurity and heat-wave deaths. Expect a big demand for energy for air conditioning as the 21st century continues.

Some of these impacts are already here, from a meltdown of polar ice and glaciers everywhere to higher rates of sea level rise than the IPCC predicted in the past. Crops, such as wheat and maize (corn), have been hurt more by heat waves and drought than helped by higher levels of CO2, which can sometimes permit more luxuriant plant growth. Some crop yields in places like northern Europe and southeastern South America where drought has not set in have actually improved.

The bad outweighs the good to date. Reductions in yields of wheat and maize have already had an impact on food prices, and some argue on the stability of nations as well. Extreme weather-from floods to wildfires-continues to take an increasing toll, and climate change will likely exacerbate existing health problems such as malaria and heat stroke. The biggest impact may prove to be changes to the availability of fresh water. All of these hazards, laid out in detail in the new report, afflict the poorest the most, particularly subsistence farmers throughout the world who depend on consistent rains for adequate food. "They are threatened in their very existence," Pachauri argued at the press conference.

Climate change will also raise the risk of conflict, whether civil war or fights between nation states over critical resources or boundaries, according to the new report. In short, climate change will make remedying existing poverty that much harder.

Opportunities still exist for adaptation, however. Communities, cities, states and nations have begun to adapt, whether improved water management in San Diego, Calif., or planting mangroves to stabilize seashores in the island nation of Tuvalu. Cimate change can be ameliorated both by cutting back on the pollution that causes it as well as by improving society to decrease vulnerability.

Future adaptation may include, for the poorest people, moving, either voluntarily or when displaced by disaster. And how societies choose to adapt will be vital as certain choices- geoengineering with artificial volcanoes or building sea walls, for example-may prove maladaptive in the long term.

The natural world has had to adapt as well, with animals and even plants moving or shifting seasonal behaviors or migration. Some marine animals have shifted their range by as much as 400 kilometers in pursuit of equally cold climes, and ocean acidification is accelerating. As the climate continues to change, species will face even greater challenges, and many may go extinct as global warming tips them into disaster when paired with other threats such as habitat loss. Entire ecosystems will be transformed, like the march of shrubs into the former tundra of Siberia and North America. "We may already be on the threshold or over the threshold of the sixth mass extinction in earth's history," Field noted.

Undercutting the optimism for ongoing adaptation is the fact that the IPCC has consistently underestimated the speed and scale of climate change. Continuing to improve the data about impacts is an ongoing challenge for the scientific community. And, in the larger view, as co-chair Field put it in his speech to open the session finalizing the new report: " Dealing effectively with climate change is one of the defining challenges of the 21st century."

ABOUT THE AUTHOR(S)

David Biello

David Biello is a contributing editor at Scientific American. He has been reporting on the environment and energy since 1999.

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Food and Water Shortages May Prove Major Risks of Climate Change

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The rich play with fire and the poor get burned. That sums up a report issued March 31 by the U.N. Intergovernmental Panel on Climate Change (IPCC) about the worsening risks of climate change. Yet even rich nations will face serious challenges.

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Water

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Most people have no idea how to select a watermelon. They just knock on this over-sized fruit as if they know what they are doing. Although it can be difficult to know how ripe a melon is by inspecting the outside, there are several tricks you can learn to help you pick the perfect watermelon.

There's a definite art to picking the very best watermelons. It involves weighing the melon between your hands, turning it over, and giving it a firm thumpon the underside. A heavy watermelon with a splotch on its belly and a hollow sound means it is brimming with juice and at the peak of its ripeness.

Buying watermelons at a farmers market takes out much of the guesswork. Farmers know their business and will only harvest watermelons for sale when they're truly ripe. When in doubt, ask the farmer to pick a melon for you. At a farmers market, you can also taste a sample and feel confident that the watermelons you take home will taste the same.
Tip For Selecting The Perfect Watermelon

1. Take A Look: Look for a watermelon that has bright skin, is firm, symmetrical, and free of cuts

2. Pick It Up: Big or small, the watermelon should feel heavy for its size. "Water" melons contain more than 90% water and the ripest ones have the most water

3. Look for the Yellow Spot: Watermelons develop a splotch from where it sat on the ground. When this splotch is creamy yellow, it's ripe.

4. Give It a Thump: Tap the underbelly of the watermelon. A ripe one will have a deep hollow sound. If not ripe enough, it will sound solid; if too ripe, it will sound thick; if perfect, it will sound hollow.

Source: The Food Network

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Tips For Selecting The Perfect Watermelon

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Most people have no idea how to select a watermelon. They just knock on this over-sized fruit as if they know what they are doing. Although it can be difficult to know how ripe a melon is by inspecting the outside, there are several tricks you can learn to help you pick the perfect watermelon.

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What types of food most have the most nutrients in them and how available they are. How food becomes nutrient rich by allowing it to change its chemical structure.  How inhibitors can affect how much nutrients are in the healthy  food you are eating.

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Minerals

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Diet rich in vitamins and essential minerals can reduce cholesterol, strengthen the immune system, speed up wounds healing and increase fertility in men. Minerals are important components of all cells.

They are necessary for creation of blood, bones and in maintaining the health of the nervous and endocrine system, muscles and blood vessels.

The lack of any essential mineral, for example potassium, could cause heart problems.

Potassium plays an important role in body processes, such as nerve and muscle function, and maintenance of fluid balance.
If you suffer from high blood pressure or if you have heart problems, consuming potassium rich food is very important for you.

There is evidence that potassium lowers blood pressure and reduces the risk of arrhythmia. Potassium is also protecting bones from osteoporosis and reduces the risk of kidney stone.

Although potassium is not directly associated with cholesterol, eating food rich in potassium can help reducing cholesterol levels in the body.

Potassium can be found mostly in orange juice, potatoes, bananas, avocados, tomatoes, broccoli, cantaloupe, apricots, strawberries, spinach and milk.

But, potassiumm can be also found in cabbage, eggplant, figs, plums, mushrooms, almonds, peanuts, cucumber, tuna, sardines, most meat products and fish.

Magnesium is important for healthy nerve and muscle functions (including heart functions). Magnesium has vital importance in proper bone growth. Whole grains, legumes, seeds and vegetables, soy products, nuts and mineral water are good sources of magnesium.

Bones contain even 98 percents of all calcium components in the body. The rest can be found in the blood, participating in metabolic functions. Calcium also plays an important role in controlling nerve potentials and muscle contractions. Dairy products, almonds and fish are the richest sources of calcium.

Zinc helps maintaining a healthy immune system. It is very important for the health of reproductive organs, especially in men. Zinc can be found in meat, fish, peas, whole grains, pumpkin seeds, mushrooms.

There is no cell in the body that does not contain sodium, so it can be found in all body fluids including blood, tears and sweat. Together with potassium and chloride, it provides proper liquid control, controlling muscle contraction and nerve cells function. Salt, salty foods and soya sauce are some of the food products containing this nutrient.

Iodine is responsible for proper development and function of thyroid gland, which is one of the central glands in the human body. Lack of iodine can cause an increase of thyroid gland, known in people as goiter. The best source of this mineral is iodized salt and yogurt and sea grass are quite good sources as well.

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Foods Rich In Minerals And Their Benefits

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Diet rich in vitamins and essential minerals can reduce cholesterol, strengthen the immune system, speed up wounds healing and increase fertility in men. Minerals are important components of all cells. They are necessary for creation of blood, bones and in maintaining the health of the nervous and endocrine system, muscles and blood vessels.

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Explains what vitamins are the different types of vitamins needed for our bodies to function. What each type of vitamins is and examples of the food it is in. Also examples how you can get some of them from chewable supplements that contain both vitamins and minerals.

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Vitamins are organic compounds that are needed in small quantities to sustain life. Most vitamins need to come from food.

This is because the human body either does not produce enough of them, or it does not produce any at all.

Each organism has different vitamin requirements. For example, humans need to consume vitamin C, or ascorbic acid, but dogs do not. Dogs can produce, or synthesize, enough vitamin C for their own needs, but humans cannot.

People need to get most of their vitamin D from exposure to sunlight, because it is not available in large enough quantities in food. However, the human body can synthesize it when exposed to sunlight.

Different vitamins have different roles, and they are needed in different quantities.

This article explains what vitamins are, what they do, and which foods provide each type. Follow the links for more information about each type of vitamin.

Fast facts on vitamins

Here are some key points about vitamins. More detail and supporting information is in the main article.

There are 13 known vitamins.

Vitamins are either water-soluble or fat-soluble.

Fat-soluble vitamins are easier for the body to store than water-soluble.

Vitamins always contain carbon, so they are described as "organic."

Food is the best source of vitamins, but some people may be advised by a physician to use supplements.

What are vitamins?

Fruits and vegetables are good sources of a range of vitamins.

A vitamin is one of a group of organic substances that is present in minute amounts in natural foodstuffs. Vitamins are essential to normal metabolism. If we do not take enough of any kind of vitamin, certain medical conditions can result.

A vitamin is both:

an organic compound, which means it contains carbon

an essential nutrient that body cannot produce enough of and which it needs to get from food

There are currently 13 recognized vitamins.

Fat-soluble and water-soluble vitamins

Vitamins are either fat-soluble or water-soluble.

Fat-soluble vitamins

Fat-soluble vitamins are stored in the fatty tissues of the body and the liver. Vitamins A, D, E, and K are fat-soluble. These are easier to store than water-soluble vitamins, and they can stay in the body as reserves for days, and sometimes months.

Fat-soluble vitamins are absorbed through the intestinal tract with the help of fats, or lipids.

Water-soluble vitamins

Water-soluble vitamins do not stay in the body for long. The body cannot store them, and they are soon excreted in urine. Because of this, water-soluble vitamins need to be replaced more often than fat-soluble ones.

Vitamin C and all the B vitamins are water soluble.

Types

Here are the different types of vitamins.

Vitamin A

Chemical names: Retinol, retinal, and four carotenoids, including beta carotene.

It is fat soluble.

Deficiency may cause night-blindness and keratomalacia, an eye disorder that results in a dry cornea.

Good sources include: Liver, cod liver oil, carrots, broccoli, sweet potato, butter, kale, spinach, pumpkin, collard greens, some cheeses, egg, apricot, cantaloupe melon, and milk.

Vitamin B

Chemical name: thiamine.

Vitamin B2

Chemical name: Riboflavin

It is water soluble

Deficiency may cause ariboflavinosis

Good sources include: asparagus, bananas, persimmons, okra, chard, cottage cheese, milk, yogurt, meat, eggs, fish, and green beans

Vitamin B3

Chemical names: Niacin, niacinamide

Vitamin B5

Chemical name: Pantothenic acid

Vitamin B6

Chemical names: Pyridoxine, pyridoxamine, pyridoxal

It is water soluble.

Deficiency may cause anemia, peripheral neuropathy, or damage to parts of the nervous system other than the brain and spinal cord.

Good sources include: meats, bananas, whole-grains, vegetables, and nuts. When milk is dried, it loses about half of its B6. Freezing and canning can also reduce content.

Vitamin B7

Chemical name: Biotin

Vitamin B9

Chemical names: Folic acid, folinic acid

Vitamin B12

Chemical names: Cyanocobalamin, hydroxocobalamin, methylcobalamin

Vegans are advised to take B12 supplements.

Vitamin C

Chemical name: Ascorbic acid

Vitamin D

Chemical names: Ergocalciferol, cholecalciferol.

Vitamin E

Chemical names: Tocopherols, tocotrienols

Vitamin K

Chemical names: Phylloquinone, menaquinones

Dietary sources

The 2015-2020 U.S. Dietary Guidelines focus on the overall diet as the best way to get enough nutrients for good health. Vitamins should come firstly from a balanced and varied diet with plenty of fruit and vegetables.

However, in some cases, fortified foods and supplements may be appropriate.

A health professional may recommend vitamin supplements for people with certain conditions, during pregnancy, or for those on a restricted diet.

Those taking supplements should take care not to exceed the stated maximum dose, as health problems can result. Some medications can interact with vitamin supplements, too, so it is important to talk to a healthcare provider before using supplements.

Video: The ABCs of vitamins

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Debra Rose Wilson, PhD, MSN, RN, IBCLC, AHN-BC, CHT

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Vitamins: What are they and what do they do?

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Vitamins are organic compounds that are needed in small quantities to sustain life. Most vitamins need to come from food. This is because the human body either does not produce enough of them, or it does not produce any at all. Each organism has different vitamin requirements.

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Vitamins

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The article is about protein is and how much we should eat based on our diet. The different food sources of protein we can get by eating a variety of foods. Also includes bad sources of protein that can make you sick if you eat too much of them.

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Protein is an essential macronutrient, but not all food sources of protein are created equal, and you may not need as much as you think. Learn the basics about protein and shaping your diet with he...

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Protein

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You should include a lean protein source at every meal. Your muscles need protein. You need the amino acids that comprise the protein we consume to repair, maintain and facilitate growth in muscles. Protein is also used in a host of other ways by the body, specifically by enzymes, blood and other cells.

Protein is a major component of all muscles, tissues and organs and is vital for practically every process that occurs within the body such as metabolism, digestion and the transportation of nutrients and oxygen in the blood. It is also necessary for the production of antibodies, which fight against infection and illness, and is the main nutrient that keeps our hair shiny and healthy, our nails strong, our skin fresh and glowing and our bones strong and healthy.

Adding protein at each meal will generally reduce the glycemic index of the meal. Focus on getting at least 1 gram of protein per pound of body weight. So, if your weight is 175 pounds, try to eat at least 175 total grams of protein per day, divided up into 5-6 smaller meals throughout the day (every 2.5 to 3 hours). Below is a list of protein packed foods to include in your muscle building plan!

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High Protein Foods List - Build Muscle with Protein Packed Food

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You should include a lean protein source at every meal. Your muscles need protein. You need the amino acids that comprise the protein we consume to repair, maintain and facilitate growth in muscles. Protein is also used in a host of other ways by the body, specifically by enzymes, blood and other cells.

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In this article it is explaining how to choose healthy fats to eat in our diet. What types of oils we shouldn't use for cooking, grilling, or frying. Includes what omega's 3 are, the foods that are rich in them and the amount of the m we should eat.

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Choosing Healthy Fats: The Good, the Bad, and the Power of Omega-3s

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Everything you need to know about dietary fat, including how to include more healthy fats in your diet.

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Fats

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The article talk about what carbohydrates are and which kinds are good/bad. What carbs we should eat and what we shouldn't eat. Also includes tip on how should eat healthy carbohydrates in your diet.

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Carbohydrates: quality matters

What's most important is the type of carbohydrate you choose to eat because some sources are healthier than others. The amount of carbohydrate in the diet - high or low - is less important than the type of carbohydrate in the diet. For example, healthy, whole grains such as whole wheat bread, rye, barley and quinoa are better choices than highly refined white bread or French fries. ( 1)

Many people are confused about carbohydrates, but keep in mind that it's more important to eat carbohydrates from healthy foods than to follow a strict diet limiting or counting the number of grams of carbohydrates consumed.

What are carbohydrates?

Carbohydrates are found in a wide array of both healthy and unhealthy foods-bread, beans, milk, popcorn, potatoes, cookies, spaghetti, soft drinks, corn, and cherry pie. They also come in a variety of forms. The most common and abundant forms are sugars, fibers, and starches.

Foods high in carbohydrates are an important part of a healthy diet. Carbohydrates provide the body with glucose, which is converted to energy used to support bodily functions and physical activity. But carbohydrate quality is important; some types of carbohydrate-rich foods are better than others:

The healthiest sources of carbohydrates-unprocessed or minimally processed whole grains, vegetables, fruits and beans-promote good health by delivering vitamins, minerals, fiber, and a host of important phytonutrients.

Unhealthier sources of carbohydrates include white bread, pastries, sodas, and other highly processed or refined foods. These items contain easily digested carbohydrates that may contribute to weight gain, interfere with weight loss, and promote diabetes and heart disease.

The Healthy Eating Plate recommends filling most of your plate with healthy carbohydrates - with vegetables (except potatoes) and fruits taking up about half of your plate, and whole grains filling up about one fourth of your plate.
Try these tips for adding healthy carbohydrates to your diet:
1. Start the day with whole grains.
Try a hot cereal, like steel cut or old fashioned oats (not instant oatmeal), or a cold cereal that lists a whole grain first on the ingredient list and is low in sugar. A good rule of thumb: Choose a cereal that has at least 4 grams of fiber and less than 8 grams of sugar per serving.

2. Use whole grain breads for lunch or snacks.
Confused about how to find a whole-grain bread? Look for bread that lists as the first ingredient whole wheat, whole rye, or some other whole grain -and even better, one that is made with only whole grains, such as 100 percent whole wheat bread.

3. Also look beyond the bread aisle.
Whole wheat bread is often made with finely ground flour, and bread products are often high in sodium. Instead of bread, try a whole grain in salad form such as brown rice or quinoa.

4. Choose whole fruit instead of juice.
An orange has two times as much fiber and half as much sugar as a 12-ounce glass of orange juice.

5. Pass on potatoes, and instead bring on the beans.
Rather than fill up on potatoes - which have been found to promote weight gain - choose beans for an excellent source of slowly digested carbohydrates. Beans and other legumes such as chickpeas also provide a healthy dose of protein.

References
1. Mozaffarian D, Hao T, Rimm EB, Willett WC, Hu FB. Changes in diet and lifestyle and long-term weight gain in women and men. N Engl J Med. 2011;364:2392-404.
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Carbohydrates: quality matters What's most important is the type of carbohydrate you choose to eat because some sources are healthier than others. The amount of carbohydrate in the diet - high or l...

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Carbohydrate