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A helpful infographic showing how animal agriculture effects green house gas emissions, water usage and land usage.

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The best way to reduce your personal carbon footprint is to reduce your use of animal products.

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Avoiding meat and dairy products is the single biggest way to reduce your environmental impact on the planet, according to the scientists behind the most comprehensive analysis to date of the damage farming does to the planet.

The new research shows that without meat and dairy consumption, global farmland use could be reduced by more than 75% - an area equivalent to the US, China, European Union and Australia combined - and still feed the world. Loss of wild areas to agriculture is the leading cause of the current mass extinction of wildlife.

The new analysis shows that while meat and dairy provide just 18% of calories and 37% of protein, it uses the vast majority - 83% - of farmland and produces 60% of agriculture's greenhouse gas emissions. Other recent research shows 86% of all land mammals are now livestock or humans. The scientists also found that even the very lowest impact meat and dairy products still cause much more environmental harm than the least sustainable vegetable and cereal growing.

The study, published in the journal Science, created a huge dataset based on almost 40,000 farms in 119 countries and covering 40 food products that represent 90% of all that is eaten. It assessed the full impact of these foods, from farm to fork, on land use, climate change emissions, freshwater use and water pollution (eutrophication) and air pollution (acidification).

"A vegan diet is probably the single biggest way to reduce your impact on planet Earth, not just greenhouse gases, but global acidification, eutrophication, land use and water use," said Joseph Poore, at the University of Oxford, UK, who led the research. "It is far bigger than cutting down on your flights or buying an electric car," he said, as these only cut greenhouse gas emissions.

"Agriculture is a sector that spans all the multitude of environmental problems," he said. "Really it is animal products that are responsible for so much of this. Avoiding consumption of animal products delivers far better environmental benefits than trying to purchase sustainable meat and dairy."

The analysis also revealed a huge variability between different ways of producing the same food. For example, beef cattle raised on deforested land result in 12 times more greenhouse gases and use 50 times more land than those grazing rich natural pasture. But the comparison of beef with plant protein such as peas is stark, with even the lowest impact beef responsible for six times more greenhouse gases and 36 times more land.

Greenhouse gas emissions for meat, dairy and pulses

The large variability in environmental impact from different farms does present an opportunity for reducing the harm, Poore said, without needing the global population to become vegan. If the most harmful half of meat and dairy production was replaced by plant-based food, this still delivers about two-thirds of the benefits of getting rid of all meat and dairy production.

Cutting the environmental impact of farming is not easy, Poore warned: "There are over 570m farms all of which need slightly different ways to reduce their impact. It is an [environmental] challenge like no other sector of the economy." But he said at least $500bn is spent every year on agricultural subsidies, and probably much more: "There is a lot of money there to do something really good with."

Labels that reveal the impact of products would be a good start, so consumers could choose the least damaging options, he said, but subsidies for sustainable and healthy foods and taxes on meat and dairy will probably also be necessary.

One surprise from the work was the large impact of freshwater fish farming, which provides two-thirds of such fish in Asia and 96% in Europe, and was thought to be relatively environmentally friendly. "You get all these fish depositing excreta and unconsumed feed down to the bottom of the pond, where there is barely any oxygen, making it the perfect environment for methane production," a potent greenhouse gas, Poore said.

The research also found grass-fed beef, thought to be relatively low impact, was still responsible for much higher impacts than plant-based food. "Converting grass into [meat] is like converting coal to energy. It comes with an immense cost in emissions," Poore said.

The new research has received strong praise from other food experts. Prof Gidon Eshel, at Bard College, US, said: "I was awestruck. It is really important, sound, ambitious, revealing and beautifully done."

He said previous work on quantifying farming's impacts, including his own, had taken a top-down approach using national level data, but the new work used a bottom-up approach, with farm-by-farm data. "It is very reassuring to see they yield essentially the same results. But the new work has very many important details that are profoundly revealing."

Prof Tim Benton, at the University of Leeds, UK, said: "This is an immensely useful study. It brings together a huge amount of data and that makes its conclusions much more robust. The way we produce food, consume and waste food is unsustainable from a planetary perspective. Given the global obesity crisis, changing diets - eating less livestock produce and more vegetables and fruit - has the potential to make both us and the planet healthier."

Dr Peter Alexander, at the University of Edinburgh, UK, was also impressed but noted: "There may be environmental benefits, eg for biodiversity, from sustainably managed grazing and increasing animal product consumption may improve nutrition for some of the poorest globally. My personal opinion is we should interpret these results not as the need to become vegan overnight, but rather to moderate our [meat] consumption."

Poore said: "The reason I started this project was to understand if there were sustainable animal producers out there. But I have stopped consuming animal products over the last four years of this project. These impacts are not necessary to sustain our current way of life. The question is how much can we reduce them and the answer is a lot."

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Avoiding meat and dairy is 'single biggest way' to reduce your impact on Earth

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Biggest analysis to date reveals huge footprint of livestock - it provides just 18% of calories but takes up 83% of farmland

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Did you know that vegans have a decreased risk of diabetes, heart disease, high blood pressure and obesity?

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Abstract

Vegetarians, those who avoid meat, and vegans, additionally avoiding dairy and eggs, represent 5% and 2%, respectively, of the US population. The aim of this review is to assess the effects of vegetarian diets, particularly strict vegetarian diets ( i.e., vegans) on health and disease outcomes. We summarized available evidence from three prospective cohorts of Adventists in North America: Adventist Mortality Study, Adventist Health Study, and Adventist Health Study-2. Non-vegetarian diets were compared to vegetarian dietary patterns ( i.e., vegan and lacto-ovo-vegetarian) on selected health outcomes. Vegetarian diets confer protection against cardiovascular diseases, cardiometabolic risk factors, some cancers and total mortality. Compared to lacto-ovo-vegetarian diets, vegan diets seem to offer additional protection for obesity, hypertension, type-2 diabetes, and cardiovascular mortality. Males experience greater health benefits than females. Limited prospective data is available on vegetarian diets and body weight change. Large randomized intervention trials on the effects of vegetarian diet patterns on neurological and cognitive functions, obesity, diabetes, and other cardiovascular outcomes are warranted to make meaningful recommendations.

Keywords: vegetarian, vegan, lacto-ovo-vegetarian, Adventist, Health, AMS, AHS, cardiovascular, cancer, mortality

1. Introduction

A recent Gallup Poll conducted in July 2012 reported that 5% of the American adult population is vegetarian. Only 2% reported adopting a vegan diet, in that they abstain from meat, fish, dairy, and eggs [ 1]. The attitudes towards vegetarianism have gained better acceptance; however, the percentage of Americans who consider themselves to be vegetarians is largely unchanged since 2001. For many individuals, the choice for adopting a vegetarian diet stems from various reasons including religious and ethical considerations [ 2], environmental impacts [ 3], and health benefits of a plant-based diet [ 4, 5]. About three decades ago, the position statement of American Dietetic Association showed reasonable doubts about the nutritional adequacy and benefits of vegetarian diets [ 6]. However, the committee has changed its positions on vegetarian dietary recommendations [ 4, 7]. This is the results of much research on vegetarian diets in the past 30 years. The increased number of publications on vegetarian nutrition and major contributions in nutritional epidemiology have contributed to better understanding of the connections between diet and disease [ 8]. In particular, studies of Adventists have provided compelling evidence that well-balanced vegetarian diets are nutritionally adequate, and associated with lower risk of chronic diseases [ 4].

Probably, the first thoughtful investigation on vegetarian diets was conducted by Mervyn G. Hardinge as a doctoral dissertation at Harvard in the early 1950s [ 9, 10, 11]. His research was initially met with resistance [ 12], but later became the founding Dean of Loma Linda University School of Public Health. His novel thinking opened up new hypotheses for subsequent research into vegetarian diets. Notably, the prospective epidemiological studies of Adventists, many of whom are vegetarians-vegans, lacto-ovo-vegetarians, semi-vegetarians, pesco-vegetarians; and about half adheres to omnivorous diets similarly to that of the general population [ 13]. Members of the Seventh-day Adventist religious denomination exhibits a variety of dietary habits, with a strong emphasis on health. Church doctrines recommend vegetarian practices and abstinence from the use of tobacco and alcohol. The range of diets consumed by Adventists is broad and distinct from the typical Western diets. Thus, this presents an ideal opportunity to compare various vegetarian dietary patterns, while controlling for known non-dietary confounders, such as the use of alcohol and tobacco [ 14].

The aim of this review is to assess the health and disease outcomes of vegetarian diets with regards to chronic diseases. Are the health effects of those who adhere to strict vegetarian ( i.e., vegan) and lacto-ovo-vegetarian diets differ from non-vegetarians? Thus, the purpose of this review is to summarize available evidence from the Adventist cohorts of potential health effects for vegan and lacto-ovo-vegetarian diets on disease and mortality; and to discuss the limitations of these diets in order to provide practical dietary recommendations.

2. Methods

In order to identify relevant articles, we conducted an independent literature review using PubMed/Medline and EMBASE databases through 28 January, 2014. The following search terms were used: "Adventist vegetarian health" (49 articles); "vegan Adventist health" (46 articles); "Adventist vegetarian cancer" (32 articles); "Adventist health BMI" (28 articles); "Adventist mortality vegetarian" (16 articles); "lacto-ovo-vegetarian Adventist" (11 articles); "Adventist health study dietary pattern" (8 articles); "Adventist vegetarian diabetes" (6 articles); and "dietary patterns Adventist mortality" (3 articles). Additionally, we cross-referenced the articles with the Adventist Health Study database of 348 articles. For the purpose of this study, only relevant articles were included using the following inclusion criteria: (1) large prospective cohort studies of Adventists; (2) reports with clearly defined dietary patterns as exposures; and (3) data of vegetarians compared to non-vegetarians (lacto-ovo-vegetarians and/or vegans) on cardiometabolic factors, cancer-related sites, and/or mortality. Exclusion criteria were: animal studies, case studies with small sample size, studies of Adventists outside of the US and Canada; studies reporting only nutrients, foods, and food groups as dietary exposures; and studies not reporting relevant health outcomes.

After careful review of thirteen articles relevant to the aim of this report, data were abstracted and tabulated according to pre-established criteria, related to the classification of the dietary patterns (), and characteristics of the study cohorts (). Eight articles were included in the comparisons between vegetarians and non-vegetarians for cardio-metabolic factors (), cancer-related sites (), and mortality (). Six articles were included in the review for lacto-ovo-vegetarians and vegans compared to non-vegetarians on cardiometabolic factors (), cancer-related sites (), and mortality (). The results extracted from these studies used various parameter estimates including means and standard deviation (SD), odd ratio (OR), relative risk (RR), hazard ratio (HR), and standard mortality ratio (SMR). Most studies reported results using the non-vegetarian group as the reference. In order to unify the results across all studies, reciprocal of the parameter estimates and confidence intervals were calculated with non-vegetarian group as the reference. In this report, we adhered to the commonly used definitions of vegetarian dietary patterns in the Adventist Health Study cohorts, as summarized in . Results are presented in a tabular format.

Table 1

Three separate prospective Adventist cohort studies, whose dietary practice and health outcomes of participants were followed. The first major Seventh-day Adventist prospective cohort study was called the California Adventist Mortality Study (AMS) [ 14, 15, 16]. This study was followed-up to disease mortality collected between 1960 and 1976, from 22,940 participants, of which 64.6% were females. The subsequent cohort study of Adventists was the Adventist Health Study-1 (AHS-1) [ 17], which started in 1976 to 1988 at the end of follow-up. It was designed to assess diet-disease associations and collect fatal and non-fatal incident events from 34,198 participants living in California, ages 25-90 years. The third and on-going prospective cohort study was the Adventist Health Study-2 (AHS-2) [ 14]. AHS-2 began in 2002 with the aim to evaluate the role of diets and lifestyle factors that may be involved in cancer-related outcomes. This is a cohort of more than 96,000 participants from US and Canada, ages 30-112 years [ 14]. Dietary data were measured at baseline using self-administered food frequency questionnaire to assess usual dietary intake, and types of dietary pattern were defined. Cancer cases were identified and matched with state tumor registries. Morality data were obtained from the National Death Index. summarizes the basic characteristics of the Adventist cohorts by location, subjects ( n), age range (years), years of follow-up (years), outcomes of interest, and study design methodology, as detailed by Butler et al. [ 14, 15, 18, 19, 20].

Adventist Cohorts and Study Participants

3. Results

For more than 96,000 participants from AHS-2 cohort, 48% were non-vegetarians, 6% were semi-vegetarians, 10% were pesco-vegetarians, 28% were lacto-ovo-vegetarians, and 8% were vegans at baseline. presents cardiometabolic risk factors comparing vegetarian and non-vegetarian Adventists. For BMI, vegetarians were approximately 2-4 points lower than non-vegetarians. After adjusted for relevant confounders, vegetarians had 55% lower odds of developing hypertension. The odds of developing type-2 diabetes was 25% to 49% lower for vegetarians compared to non-vegetarians in different cohorts. The odds of developing metabolic syndrome (MetS) for vegetarians were about half compared to non-vegetarians.

presents results comparing risks of all-cancer and cancer-specific sites between vegetarian and non-vegetarian Adventists. Vegetarians experienced a modest, 8% risk reduction for overall-cancer. For cancer-specific sites, vegetarians had approximately half the risk of developing colon cancer. Also, vegetarians had 23% risk reduction for cancer of the gastrointestinal tract. Vegetarians experienced a 35% risk reduction for prostate cancer compared to non-vegetarians. Similarly, vegetarians tended to have lower risk for cancer of the respiratory tract and overall-cancer. No significant differences between the diet groups were found for other site-specific cancers including lung, breast, and uterine.

presents all-cause and cause-specific mortality comparing vegetarians to non-vegetarians. In all three cohorts, vegetarians experienced a 10% to 20% decreased in all-cause mortality. Similarly, vegetarians had 26% to 68% lower risks of mortality from ischemic heart disease, cardiovascular disease, and cerebrovascular disease. Vegetarians experienced a 48% risk reduction in mortality from breast cancer, and modest risks reduction from other-cause total mortality. No significant risks reduction in cause-specific mortality were found among vegetarians, particularly for cancers of the stomach, colorectal, lung, and prostate.

presents cardiometabolic-related factors comparing vegan and lacto-ovo-vegetarian Adventists to the non-vegetarian counterparts. Lacto-ovo-vegetarians and vegans had respectively, 3 and 5 points lower BMI than non-vegetarians. For hypertension, lacto-ovo-vegetarians experienced 55% lower risks; whereas, vegans had 75% risks reduction when compared to non-vegetarians. Similarly, lacto-ovo-vegetarian and vegan were associated with lower risks of type-2 diabetes. The risks reduction of diabetes for lacto-ovo-vegetarians varied between 38% and 61%; and 47% to 78% for vegans. When stratified by ethnicity, the relative risks reduction for diabetes was greater in blacks than non-blacks when compared with their non-vegetarian counterparts. For all cardiometabolic-related outcomes, vegans had lower risk than lacto-ovo-vegetarians compared to non-vegetarians.

presents all-cancer and site-specific cancers for vegan and lacto-ovo-vegetarian Adventists compared to non-vegetarians. Overall, vegans experienced modest risks reduction (14%) for all-cancer, but not significant for lacto-ovo-vegetarians. When stratified by gender, no significant differences were observed in the hazard ratio for all-cancer in vegans. Conversely, lacto-ovo-vegetarians conferred 24% risks reduction for cancer of the gastrointestinal tract, but not significant for vegans. Vegans experienced 73% higher risk for urinary tract cancer compared to non-vegetarians. Neither vegans nor lacto-ovo-vegetarians had significant risks reduction for cancer of the respiratory tract.

presents results for all-cause and cause-specific mortality comparing lacto-ovo-vegetarian and vegan Adventists to non-vegetarians. Lacto-ovo-vegetarians experienced a 9% risks reduction for all-cause total mortality. Vegan had 14% lower risks of all-cause mortality in males. Lacto-ovo-vegetarian and vegan males experienced a 23% and 42% risks reduction in CVD mortality, respectively. Vegan males also had a 55% risk reduction for ischemic heart disease. Overall, the risks reduction in all-cause and specific-cause mortality were greater in males than females.

4. Discussion

The published studies of North American Adventists paint a consistent picture across all three study cohorts, associating vegetarian diets with lower body mass index [ 21, 22, 29], coronary heart disease [ 19, 30], hypertension [ 18, 21], type 2 diabetes [ 15, 21, 23, 28], and metabolic syndrome [ 29]. Similarly, vegetarians have lower risks for colon, gastrointestinal tract, prostate and overall cancer. Among males, vegetarian diets seem to be protective against all-cause mortality and CVD mortality. Results for some diseases such as breast cancer mortality are not always consistent within the earlier Adventist cohorts [ 26, 31, 32, 33, 34]. The lower risk among vegetarians of several high prevalent chronic diseases results in a greater life-expectancy compared to non-vegetarians. Although, Adventist males tend to live 7.3 years and females 4.4 years longer than their gender counterparts in the general Californian population [ 15, 35], within the same cohort, vegetarians had more modest 1.5 to 2.4 years longer life-expectancy than non-vegetarian Adventists [ 35]. This suggests that other non-dietary factors of the Adventist lifestyles may also contribute to their longevity.

The other major vegetarian cohort is the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford) study where 65,429 participants were recruited from the United Kingdom, many of whom are vegetarians [ 36]. Similar to Adventist vegetarians, British vegetarians enjoy lower rate of cardiovascular disease and risk factors compared to their non-vegetarians British counterparts [ 37]. In the EPIC-Oxford cohort study [ 38, 39, 40], the total incidence of all cancers was lower among vegetarians than meat eaters; however, colorectal cancer rates were greater than the non-vegetarians [ 38]. Another study reported no difference in total mortality between British vegetarians compared with other health-conscious participants [ 41]. A pooled analysis has shown reductions only for IHD mortality [ 25]. A possible explanation for the discrepancy between British vegetarians and US Adventist vegetarians may be related to differences in diets other than the absence of meat [ 27]. Vegetarians and vegans from the Adventist cohorts consume more fiber and vitamin C than those of the EPIC-Oxford [ 29, 36]. It has been previously noted that the lack of consistent findings from British vegetarians deserves further attention [ 27, 42], since other non-dietary lifestyle factors may also differ between the two vegetarian cohorts.

Beyond meatless, there is a need to evaluate the health effects of different types of vegetarian diets. How does the health status of lacto-ovo-vegetarians and vegans differ from non-vegetarians? In the Adventist cohorts, both lacto-ovo-vegetarians and vegans have reduced risk for hypertension, type 2 diabetes, and obesity; however, vegans experienced greater risks reduction for those diseases. Similarly, both lacto-ovo-vegetarian males and vegan male have lower mortality from cardiovascular disease compared to non-vegetarians, but risk reduction is greater among vegans. In contrast, both lacto-ovo-vegetarian and vegan females do not seem to have a lower risk of mortality from cardiovascular diseases. Not so clear patterns are observed for cancer outcomes. While lacto-ovo-vegetarians have lower risk of cancer of the gastrointestinal tract, vegans experience a higher risk for cancer of the urinary tract. For other-cancer sites, the risk is slightly but not significantly lower for both lacto-ovo-vegetarians and vegans compared to non-vegetarians. Subsequent reports with longer follow-up time and more cancer cases will help clarify the role of specific vegetarian diets with cancer outcomes.

Several proposed mechanisms may explain the lower risks for some diseases exhibited by vegans compared to lacto-ovo-vegetarians. It is well established that obesity is a major risk factor for CVD [ 43, 44, 45, 46] and cancer [ 47, 48, 49, 50, 51]. Significantly lower mean BMI observed in vegans may be an important factor for reducing risks from heart disease and CVD mortality [ 36]. Nutrient profiles of the vegetarian dietary patterns may explain cardiovascular risks reduction [ 29]. Dietary fibers, folate, antioxidants, and phytochemicals rich in fruits and vegetables [ 52, 53], whole grains, soy, and nuts [ 54, 55, 56] are associated with low level of serum cholesterol [ 57], lower trans/saturated fat, lower incidence of diabetes [ 58], CVD [ 59], and specific cancers [ 60], and lower mortality incidence from stroke and IHD [ 61]. Other published studies of vegetarians also found that vegans are thinner [ 62], have lower LDL and total cholesterol [ 63] than lacto-ovo-vegetarians, among whites and African Americans [ 64]. Similarly, among Latin Americans, vegans have lower plasma lipids than lacto-ovo-vegetarians and omnivores [ 65]. Vinagre et al. [ 66] showed that vegan diets improved metabolic pathways of cholesterol remnant removal from circulation.

Vegans may have a greater challenge in meeting the nutritional adequacy for vitamin B ₁₂, protein, and calcium compared to lacto-ovo-vegetarians and meat-eaters. Thus, the potential adverse effects of vegan diets deserve consideration. In the EPIC-Oxford study [ 67], vegans had 30% higher fracture rates than meat-eaters. However, when adjusted for calcium intake, vegans no longer had higher fracture rate. Other studies found similar results [ 68]. In a review, Dunham et al. reported higher rates of vitamin B ₁₂ deficiency among vegans compared with other vegetarians [ 69]. Vitamin B ₁₂ deficiency may increase CVD risk factors [ 70], and is associated for a wide range of neurological disorders [ 71]. In addition, for those following a vegan diet, optimizing intakes of n-3 fatty acids is highly recommended [ 72, 73, 74]. Nevertheless, vegans can avoid nutritional inadequacy with appropriate food choices [ 4, 7, 72].

Strengths and Limitations

The strength of this review is its focus on only prospective studies of vegetarian Adventists. The Adventist population places high emphasis on health and exhibits diverse dietary habits [ 14], with relatively low percentage of alcohol consumption and cigarette smoking. Thus, this reduces possible confounding due to non-dietary factors, and results in greater statistical power. In addition, the consistent and refined operational definitions of dietary patterns offer an advantage in measuring the relationship between vegetarian diets and disease/mortality outcomes.

Since this review is limited to the Adventist cohorts, the findings may not be fully generalizable to other vegetarians with different lifestyles. The studies in our review did not directly compare vegans with lacto-ovo-vegetarians, thus it may not provide adequate interpretation of the magnitude of differences in effect size between these two dietary patterns. The observed health benefits of vegetarians may be partially related to other lifestyle factors due to residual confounding. Dietary patterns may change over time, which has not been accounted for in the analysis. These studies, like any others using the food frequency questionnaires, include unavoidable measurement errors in the assessment of food consumptions. However, in the Adventist population, we have reported good validity for the foods used in defining the different types of vegetarian diets [ 75]. Non-vegetarian Adventists, used as a reference in all reported comparisons, consume much less meat than the general population [ 35, 76]. Thus, the relatively low intake of meat by this reference group in this cohort may result in smaller observed effects. Relative small sample size within the vegan groups may limit our conclusions.

The research on the health effects of vegan diets and chronic diseases have mostly derived from observational studies of Adventist and Oxford vegetarians cohorts. These studies have mainly focused on cardiovascular disease and cancer outcomes. Further research is needed in the prospective investigation of obesity, diabetes, cognition, and other neurological disorders. Given the consistency of results from prospective epidemiological studies on vegetarian diets and cardiovascular disease, large randomized dietary intervention trials on vegan and lacto-ovo-vegetarian patterns are warranted to duplicate the findings and further investigate the health effects of these diets.

5. Conclusions

In summary, vegetarians have consistently shown to have lower risks for cardiometabolic outcomes and some cancers across all three prospective cohorts of Adventists. Beyond meatless diets, further avoidance of eggs and dairy products may offer a mild additional benefit. Compared to lacto-ovo-vegetarian diets, vegan diets seem to provide some added protection against obesity, hypertension, type-2 diabetes; and cardiovascular mortality. In general, the protective effects of vegetarian diets are stronger in men than in women. At present, there are limited prospective data on vegetarian dietary patterns and body weight change, obesity and neurological disorders. Large dietary intervention trials on the effects of vegetarian diets on obesity, diabetes, and cardiovascular outcomes are warranted to make meaningful recommendations for nutritional planning, assessment, and counseling.

Acknowledgments

All authors have primary responsibility for the final content and read and approved the final manuscript. The work was funded in part by NIH/NCI grant, NIH R01-CA094594. Special acknowledgement to Gina Siapco for her editorial comments in a previous version of the manuscript.

Conflicts of Interest

The authors declare no conflict of interest.

References

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Beyond Meatless, the Health Effects of Vegan Diets: Findings from the Adventist Cohorts

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Vegetarians, those who avoid meat, and vegans, additionally avoiding dairy and eggs, represent 5% and 2%, respectively, of the US population. The aim of this review is to assess the effects of vegetarian diets, particularly strict vegetarian diets (i.e., ...

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According to the Academy of Nutrition and Dietetics, yes for all stages of life. "It is the position of the Academy of Nutrition and Dietetics that appropriately planned vegetarian, including vegan, diets are healthful, nutritionally adequate, and may provide health benefits for the prevention and treatment of certain diseases. These diets are appropriate for all stages of the life cycle, including pregnancy, lactation, infancy, childhood, adolescence, older adulthood, and for athletes."

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Position of the Academy of Nutrition and Dietetics: Vegetarian Diets. - PubMed - NCBI

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Can you 'humanely' kill something that doesn't want to die?

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The linked documentary (Dominion 2018) shows footage from factory farms, slaughter houses, fur farms and animal testing facilities. The footage is extremely disturbing and upsetting. It should absolutely not be viewed by anyone under the age of 18 or anyone who is sensitive to images and videos of extreme animal abuse and torture. Never the less, it is an important lesson in where our food comes from and the conditions in which these animals are raised and killed. Please understand that by giving your money to these businesses, this torture and suffering persists.

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DOMINION 2018 - Full Documentary narrated by Joaquin Phoenix

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Vegan men in this study averaged higher levels of testosterone than their omnivore and vegetarian counterparts.

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While work is being done on lab grown meat (which does not result in animal deaths and uses less land and water) the best thing to do until it is available is limit your use of animal products.

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Meat grown in a laboratory could be on restaurant menus by the end of the year, one manufacturer has claimed.

In vitro animal products, sometimes referred to as " clean meat ", are made from stem cells harvested via biopsy from living livestock, which are then grown in a lab over a number of weeks.

Some environmentalists believe the process could be the key to reducing global warming, with one study predicting it could lower harmful greenhouse emissions by 96 per cent.

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And the first products could be available for human consumption within months, according to Josh Tetrick, CEO of clean meat manufacturer JUST.

Chicken nuggets, sausage and foie gras created using the technique could be served in restaurants in the US and Asia "before the end of 2018", he told CNN.

But public perception and a reluctance to diverge from traditional farmed meat still represent considerable hurdles for the clean meat industry to overcome, he said.

"Gnarly problems, communication issues, regulatory issues," would have to be solved before products went to market, he said in a separate interview with The Guardian.

His stance is shared by Mosa Meat, whose lab based at Maastricht University in the Netherlands, was responsible for creating the world's first cultured hamburger.

The company's chief scientific officer Professor Mark Post said the regulatory approval process could delay samples being distributed to suppliers by years.

He gave a time frame of three years before the company could sell its first product to the mass market.

But one recent study revealed one third of Americans would be willing to eat clean meat regularly or as a replacement for farmed meat.

To reach that point, companies will have to bring down the cost of mass production.

Memphis Meats, a food technology company based in San Francisco, has to spend around $2,400 (£1,800) to make 450 grams of beef.

But as techniques become more streamlined, the price is falling, and the company believes it will be able to send the first products to market by 2021.

Animal rights charity Peta has been investing in in vitro meat research for the past six years.

In 2014, it offered a $1 million (£725,000) reward to the first scientist to produce and bring to market in vitro chicken meat.

"We believe it's the first important step toward realising the dream of one day putting environmentally sound, humanely produced real meat into the hands and mouths of the people who insist on eating animal flesh," the charity said in a statement.

An estimated 14.5 per cent of the planet's global warming emissions stem from from the keeping and eating of livestock - more than from the entire transport sector.

Livestock emit methane, a potent greenhouse gas, while land clearing and fertilisers release large quantities of carbon.

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Lab-grown 'clean' meat could be on sale by end of 2018

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Meat grown in a laboratory could be on restaurant menus by the end of the year, one manufacturer has claimed. In vitro animal products, sometimes referred to as "clean meat", are made from stem cells harvested via biopsy from living livestock, which are then grown in a lab over a number of weeks.