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Is a Strict, 100% Vegan Diet Optimal (for Everyone)?

by Thomas E. Billings

Copyright © 2010 by Thomas E. Billings. All rights reserved.
Contact author for permission to republish.




Note: a condensed and edited version of the material below was posted on the Fresh Network blog on 12 Feb 2010, at the URL:

Here we provide:

  • an earlier draft of the main article that includes some content that was excluded from the final posted version,
  • an edited version of my reply to the pro-vegan article at the URL above,
  • replies to some comments made on the Fresh Network blog, and
  • supplementary information on select topics.



[Main article]


A 100% vegan diet – done intelligently – can work well for many people, but that does not mean it is optimal for everyone.  A vegan diet can be unhealthy, e.g., diets based on junk foods or soy meat analogues. Those attempting strict vegan diets are advised to pay attention to their nutrition.


Nutritional issues


Vitamin B-12. A vegan diet needs a reliable source of vitamin B-12. Plant foods can contain some vitamin B-12, which is absorbed from soil and water (Mozafar 1994). However, the amount varies with the B-12 content of the soil (some soil has no B-12), so plant foods alone are not a reliable source (Billings 1999). A group of vegan nutritionists recommends that vegans take B-12 supplements or consume (processed) foods fortified with B-12 (Walsh 2001). Some advocates suggest regular blood testing and using supplements only if indicated, an approach that appears over-cautious given the low cost and safety record of B-12 supplementation.


Essential fatty acids (EFA).  It can be difficult to get adequate amounts of EFAs on low-fat vegan diets. There are two primary types of EFA:  omega-3 (n-3) and omega-6 (n-6). Vegan diets are usually very low in n-3 (ALA: alpha-linolenic acid) and higher in n-6 (LA: linoleic acid). The Institute of Medicine (2005) suggests adequate intakes (AI) for LA of 17 and 12 grams/day for men and women; for ALA 1.6 and 1.1 grams/day.  


Both ALA and LA can be converted to long-chain metabolites, including EPA: eicosapentaenoic acid and DHA: docosahexaenoic acid. A large body of research shows that EPA and DHA are extremely important for health, and that vegans and vegetarians typically have lower levels of these than non-vegetarians. These long-chain fatty acids are available directly in many animal foods, especially cold-water fish, but generally not provided in vegan diets, though seaweed and some algaes may contain small quantities (Davis & Kris-Etherton 2003).


The conversion to EPA, DHA depends on many factors, including the n-6/n-3 ratio in the diet. Because the conversion is inefficient, some researchers recommend double the AI for ALA in vegans/vegetarians. “A balance of 2:1 - 4:1 (n-6:n-3) appears optimal for vegetarians and others who do not receive preformed EPA and DHA.” (Davis & Kris-Etherton 2003, p. 643S). Some vegan nutritionists suggest including flaxseed (oil) or certain nuts in the diet to provide n-3 EFAs, and vegan DHA supplements are available.


Genetics may be a factor (for some individuals) in the conversion to EPA, DHA. Individuals descended from populations that consumed significant quantities of fish (fresh and/or salt-water) over a long/evolutionary period of time might not produce adequate levels of the enzymes required for conversion (Davis, personal communication; also see Simopolous 1999). This may be relevant to, for example, some people from: Ireland (McQuade & O'Donnell 2007), Britain (Richards et al. 2005, 2006; Bocherens & Drucker 2006), Northern Spain (Adán et al. 2009).


That low fat vegan diets may fail to provide adequate EFA intakes is demonstrated in Doug Graham’s The 80/10/10 Diet book; on p. 118 he gives a sample day’s menu that fails to meet a man’s AI for ALA, barely meets a woman’s AI for ALA, and provides only a small percentage (8.2-11%) of the AI for LA (Graham 2008). If we follow the recommendation to double the AI for ALA for vegetarians, Graham’s sample day-menu provides a mere 41% of recommended ALA levels for men and 59% for women. One wonders what risks are implied in insufficient EFA intake over the long term, especially in those who have poor conversion to EPA/DHA. Unfortunately, the current anti-fat phobia in the raw vegan community may actually discourage raw fooders from consuming adequate EFAs.


Other supplementation may be appropriate for optimal health:

  • Choline is important for certain brain functions and lipid transport/metabolism. Strict vegans should consume choline-rich foods (legumes, grains) or consider supplements. Most fruits and vegetables are low in choline (Zeisel & Niculescu 2006).
  • Vitamin D: The likelihood that the AI levels for vitamin D are too low is currently a “hot topic” in nutrition research. Vitamin D is usually not present in plant foods. However, modern technology provides an exception: certain mushrooms that are exposed to ultraviolet light in post-harvest processing can provide some vitamin D (Roberts et al. 2008; Koyyalamudi et al. 2009).  Modern lifestyles also make it difficult to get adequate vitamin D from sunshine-based synthesis. Vegan vitamin D supplements are available.
  • Calcium is present but has low bioavailability in many green vegetables and some seeds.
  • Zinc, iron may be concerns on restricted diets.


Vegetarian advocacy: rhetoric vs. reality


Model diets cited by vegetarian advocates are non-vegetarian and based on cooked starches. The traditional diet of Okinawa is sometimes cited as a model diet that promotes health and longevity. Willcox et al. (2007) report that the Okinawa diet in 1949 was 85% carbohydrate, 9% protein, and 6% fat. The diet was non-vegetarian and included fish and seaweed. The traditional diet of Okinawa was “sweet potato and miso soup with plenty of vegetables for breakfast, lunch and dinner” with meat (usually pork) consumed at festivals. (Sho 2001; quote from p. 161).


In a similar vein, on pg. 69 of his book, Doug Graham repeats information from John Robbins, showing similar high-carb, cooked-starch-based, non-vegetarian diets as models. The diets are labeled as from Abkhasia, Vilcabamba, and Hunza; these are allegedly long-lived cultures but that claim is highly suspect (Tu 1999).  Note that extensions of this model diet data to 100% raw, 100% vegan, and/or fruit-based diets constitute extrapolations beyond the range of the data.


Beware of misleading comparisons in nutritional research. Vegetarian advocates often cite research studies when promoting the diet. However, just as there are many different vegan diets, so too there are many different omnivorous diets. Results of research on people following the SWD - the standard Western diet - are often interpreted as a proxy for all omnivorous diets. This is misleading and inaccurate; it is well-known that the SWD is unhealthy and too high in calories, fat, sugar, and salt. An omnivorous diet with a low level of animal products can be based primarily on unprocessed or minimally processed foods and be a healthy diet (the model diets above are examples).


Results from biomedical research studies on self-identified vegetarians also can be misleading. Individuals who eat limited amounts of meat – only fish or non-red meat – often self-identity as vegetarians (Barr et. al., 2002; Haddad and Tanzman, 2003). This means that a study that compares the SWD to self-identified vegetarians is actually comparing a high-meat group to a lower-meat group!


Can you see the contradiction and irony here: based on studies that used the SWD, some vegetarian advocates condemn all omnivorous diets (an obvious logical fallacy), while at the same time presenting the healthy omnivorous diets of Okinawa, Abkhasia (and other locales) as models. The possibility that some of the research studies cited by advocates may be based on self-identified “vegetarians” who really are low-meat non-vegetarians, increases the irony.


Vegan naturalism:  realistic or idealistic?


Raw vegan diets are often promoted as the “most natural” diet. Such claims are based on a view of nature that is naive, idealistic, and inaccurate. Some sample beliefs about nature include:

·         Humans don’t need tools to acquire or consume their natural diet.

·         Nature gives you perfect foods that are ready to eat.

·         These natural foods are easy to acquire, and abundant.

·         A diet based on these foods will grant perfect health and prevent/cure disease.

Consider the roots of the natural hygiene movement: some health reformers in the 1800’s were ministers who mixed religious teachings with dietary teachings (e.g., Sylvester Graham), and traditional Christianity was dominant at the time. Given this background, one must ask: could the anthropocentric, benevolent view of nature described above be derived from (or influenced by) the Garden of Eden story from the Bible? Is the raw vegan/natural hygiene “scientific” view of nature really a recycled religious view?

A more realistic view is to observe that the range of our natural diet is defined by evolution, which for humans includes tool use and the effects of language and culture, all of which are strong evolutionary selective pressures. The natural human diet is a hybrid between a non-vegetarian hunter-gatherer diet and the plant-based agricultural diets that have dominated since the Neolithic revolution. Where each individual falls in that range will vary according to genetics and other factors.

An important reminder: we live in an unnatural world, and hunter-gatherer or Neolithic subsistence farmer lifestyles are not feasible nowadays. The fact that some of your genes were inherited from hunter-gatherers does not justify a diet based on modern feedlot meats. We are alive here and now; the relevant question is: what sustainable diet(s) can work well for us? A false, Edenic view of nature is not helpful in answering this important question.

Maximizing the probability of success on vegan diets


Strict vegans need to make intelligent food choices to avoid problems: eat mostly unprocessed foods, take a B-12 supplement, pay attention to your EFA intake (supplementation may be appropriate), consider other supplementation if relevant, and base your diet on the widest range of vegan foods possible: vegetables including greens, roots & tubers; fruits,  nuts, seeds, seaweed, sprouted (or conservatively cooked): grains, legumes.


Finally, if 100% raw vegan does not work, options available include supplementation, increasing consumption of cooked foods, and/or including non-vegan foods in your diet. Remember that your diet should serve you, and not the other way around.


Note: References are listed at the end, including a link to free full text of the EFA article by Davis & Kris-Etherton (2003). Vegans who want evidence-based information on EFAs are strongly encouraged to read that article.


Thomas E. (Tom) Billings

Berkeley, California, U.S.A.

26 Jan 2010




Edited reply to/comment on pro-vegan article on Fresh Network blog


Note: I won’t post the pro-vegan article or its comments; it is available via the Fresh Network blog article URL at the top of this page. Consequently, that makes posting my reply to the pro-vegan article more difficult, as there is no context for it. To enable posting here, I have chosen to edit my reply to remove references to the other author. What remains is posted here as it is directly related to the main article topic.



Use of supplements. Dr. Michael Klaper recommends that vegans use supplements: vitamin B-12, DHA, multivitamins (Klaper 2008A,B,C). In a separate interview, Dr. Klaper repeated the suggestions to supplement, and made the interesting remark: "...we see most people do quite well on vegan diets. But, there are some folks who will lose muscle mass, experience lower energy levels and not feel at their best eating a vegan diet." (Klaper as quoted in Horton, 2009). Any claim that Klaper says that (unsupplemented) vegan diets are nutritionally complete, is clearly incorrect.


The original China Study is an ecological study; such studies may generate hypotheses but they prove nothing. The China Study report lists only 6 statistically significant correlations between meat-eating and disease mortality. Further, 4 of those correlations are negative, which indicates that the mortality rate for that disease decreased as meat consumption increased. The direct evidence of the study is hardly the condemnation of meat consumption that vegan advocates may claim it to be (Billings 1999B).


Re: the “humans are frugivores” claim made by some vegan advocates. It is hard to understand why this claim is so important to some vegans, when one considers that nonhuman primate frugivores are generally non-vegetarian. That is, even if humans are frugivores, it does not mean that we are natural vegetarians, e.g., chimpanzees and bonobos are frugivores and they are non-vegetarian. (Hunting by chimpanzees is common and well-documented; less well known is that bonobos also hunt animals for food.)


The idea that humans cannot eat animal foods because we lack claws and fangs is invalid because tool use made those adaptations unnecessary. Humans have used tools since our inception as a species; the natural hygiene teaching that humans are ”naked apes without tools” is a fantasy.


The “humans are frugivores” claim falls apart under cursory examination. Let’s assume that humans are obligate frugivores adapted to high-fruit vegan diets. That would imply:

·         A highly specialized diet means we are adapted only to a narrow ecological niche, and we should not have succeeded outside the tropics.

·         Over the course of evolution, human tribes that adopted fruit-based diets should have out-reproduced the tribes who ate animal foods, i.e., fruit-based diets should be the norm.

·         Long-term success should be the norm on high-fruit diets; instead we see a high failure rate.

·         In order to pick the fruit that is supposed to be the basis of our diet, humans should be quadrupedal (like chimps) and have the special adaptations for tree climbing that many non-human primates have.

With so many obvious fallacies in the “humans are obligate frugivores” claim, why does anyone promote such misinformation?


Re: claims that humans have a single, narrow “species-specific” diet. The reality is that our species-specific dietary range is defined by evolution. Humans are generalists who not only have survived, but thrived and colonized the entire planet (land area, excluding Antarctica). Because of our evolutionary history: diverse environments, cultures, and diets, humans have adapted to a range of diets.


Re: importance of vegan morals. Evolution is an amoral force, driven by species survival in the face of selective pressures. Vegan moral preferences are irrelevant in evolution. Similarly, natural hygiene myths about humans living on fruit diets in an Edenic paradise are also irrelevant.


In closing, let’s return to the important question posed in my article: what sustainable diet(s) can work well for us? If you thrive on them, then raw, vegan, or vegetarian diets may be part of your answer to this question. However, consider that diet gurus who promote idealistic and “perfect” diets (for their own financial gain) don’t necessarily have your interests at heart, and be open to the possibility that you may need to supplement and/or modify your diet to thrive, long term.



Supplement and replies to comments on Fresh Network blog posting:


Blog comment on EFAs.


One commenter questioned the paragraph:


Genetics may be a factor (for some individuals) in the conversion to EPA, DHA. Individuals descended from populations that consumed significant quantities of fish (fresh and/or salt-water) over a long/evolutionary period of time might not produce adequate levels of the enzymes required for conversion (Davis, personal communication; also see Simopolous 1999). This may be relevant to, for example, some people from: Ireland (McQuade & O'Donnell 2007), Britain (Richards et al. 2005, 2006; Bocherens & Drucker 2006), Northern Spain (Adán et al. 2009).


The commenter pointed out that one of my citations is from an archeological journal, but does not explain why that is objectionable. I can only guess that the person is questioning how long it would take for fish consumption to impact (in a hereditary way) EFA metabolism.


The archeological journal citation is Adán et al. (2009); the article in question is titled “Fish as diet resource in North Spain during the Upper Paleolithic.”   Another citation one might question here is McQuade & O'Donnell (2007). That paper was cited because of the following quote, from pp. 578 and 580 of the article:


“It has long been recognised that fish were a valuable resource which was exploited from early prehistoric times (Clarke 1948)...The population of Ireland was especially reliant on fish because the limited fauna resident on the island provided little opportunity for hunting (van WijngaardenBakker 1983: 39;Mitchell 1990: 75;Woodman et al. 1997). This dependence on fishing is evident from the marked concentration of Mesolithic material recovered from lakeside, riverine and coastal settings (Woodman 2003: 8-10). Moreover fish formed a significant percentage of the faunal remains from both coastal and inland sites of the period (Waddell 1998: 13; Woodman et al. 1999: 142).”


In retrospect, it might have been better to cite Clark (1948), which starts with a discussion of fishing in Europe during the Upper Paleolithic period:


Clark JGD, 1948. The Development of Fishing in Prehistoric Europe. The Antiquaries Journal, 28: pp. 45-85. (Note the correct spelling of the author’s name: Clark.)


The commenter also challenged Simopolous (1999), based only on reading the abstract. The reference here is to Tables 3 & 4, pp. 563S-564S of Simopolous (1999), which serve as pointers to the underlying factor: the well-known fact that fatty acids are involved in gene expression (gene-nutrient interactions). “It has been shown that fatty acids rapidly and directly alter the transcription of specific genes (49)” (Simopolous 1999, p. 561S).


Nutritional regulation of gene expression can “produce changes that define phenotypic expression” (Cousins 2006, p. 615). Nutrient-gene interaction can serve as a kind of feedback control mechanism that directly impacts genetics and evolution (Hargrove & Berdanier 1993).


The interaction between gene expression and evolution is currently an area of active research. My paragraph on the topic was carefully worded, e.g., “over a long/evolutionary period,” because I am not aware of any studies that examine the length of time required (i.e., number of generations) for the downregulation of the enzymes to create DHA, EPA that is induced by fish consumption, to have an impact in a human population.


One study on the interrelationship between evolution and gene expression compared DNA and RNA arrays for humans, chimpanzees, orangutans, and rhesus macaques. Statistical analysis of the arrays showed rapid evolution of human transcription factors (recall that fatty acids are involved in transcription). The study notes: “These observations suggest that genes with expression levels under directional selection [i.e., transcription] in humans are somewhat more likely to show accelerated amino acid evolution.”  (Gilad et al. 2006, p. 244; also see Nielsen 2006). However, this does not tell us how long it would take for fish consumption to have an impact on hereditary ability to synthesize EPA, DHA.


A personal note to the commenter who falsely accused me of not wanting readers to check the references: the fact is that I want you to check the references that I cite, whenever it interests you. But please note that, with very few exceptions – which I usually specify in the relevant reference list – I work from full text and not from abstracts only. I encourage you to follow the same practice: obtain and read full text; don’t rely on abstracts only.


And please, for your own benefit, start demanding that the raw/veg diet gurus back up any important claims with references and citations to the scientific literature. If the gurus actually supply citations, then be sure to check those too when they are of interest.


Any time that a diet guru makes exaggerated or nonsensical claims, challenge him or her to provide support for those claims. Example: if your diet guru claims that there are “thousands of studies” to support his/her claims, then why can’t he/she quickly and easily supply you with, say, 50 citations in support of the claim? Another example: a diet guru who talks of “hundreds of thousands” or “countless” nutrients; ask him/her to point you to the large databases that contain lists and documentation for these (mysterious) nutrients.


Blog comment on the China study.


My reply paragraph on the China Study was very carefully worded: “The original China Study” was specified because the material I was replying to was ambiguous. There are two books that could be identified as “The China Study,” and when no citation is given I cannot tell which book is the subject.


The original China study refers to:


Junshi C, Campbell TC, Junyao L, Peto R, 1990. Diet, Life-style, and Mortality in China, Oxford University Press.


A later followup book by Campbell, The China Study, was published in 2005. My comments refer to the 1990 book because it is the more credible of the two references.


Supplement on choline.


Choline is a complex nutrient. Humans can synthesize it but we should not rely on self-synthesis: “The presence of a pathway for endogenous synthesis [of choline] does not make it a dispensable nutrient for most animals or humans” (Zeisel & Niculescu 2006, p. 525). Betaine is a metabolite of choline, so consuming foods that contain betaine may reduce choline requirements. Choline can also be degraded (to betaine) by gut bacteria, and this process can reduce net absorption of choline (Zeisel & Niculescu 2006).


Choline is extremely important for brain development, especially the hippocampus, the part of the brain involved in memory. This makes it very important for pregnant or lactating women:


“Pregnancy and lactation are periods when maternal reserves of choline are depleted. At the same time, the availability of choline for normal development of brain is critical…Lack of choline in a mother’s diet during pregnancy and lactation may have life-long effects on their child.” (Zeisel 2004, p. 621S).



Supplement on EFAs.


AI controversy.  As stated above, the Institute of Medicine (2005) suggests adequate intakes (AI) for LA of 17 and 12 grams/day for men and women; for ALA 1.6 and 1.1 grams/day.  Another study (Simopolous et al. 1999B) recommends, for a 2000 calorie daily diet:


·         LA:  AI = 4.44 grams  with UL (upper limit) 6.67 grams

·         ALA:  AI = 2.22 grams

·         (DHA + EPA) total AI =  0.65 grams, with DHA at least 0.22 grams, EPA at least 0.22 grams.


The AIs suggested above are different from those of the Institute of Medicine (2005). The AI for LA, per the Institute of Medicine, is above the UL suggested above. Also note that the Institute of Medicine does not provide an AI for DHA, EPA. As a standards-setting organization, the Institute of Medicine recommendations change at a glacial pace.  Other nutritional advisory groups are not as slow; many such groups around the world now recommend minimum daily intakes for EPA & DHA; see Kris-Etherton et al. (2009) for a summary list of the organizations and recommendations. Needless to say, meeting a daily AI for direct intake of DHA, EPA on a strict vegan diet requires supplementation.


The Institute of Medicine recommendations must also be viewed in context: the diets used as basis for the AIs ranged from 15-40% fat. Meeting the Institute of Medicine AIs on a 10% fat diet, with good n-6/n-3 ratio, may be problematic as discussed below.


Role of body fat reserves. "Relatively large reserves of LA in body fat, as are found in vegans or in the diet of omnivores in Western societies, would tend to slow down the formation of long-chain n-3 fatty acids from ALA" (Simopolous 1999, p. 563S). This factor may be particularly relevant during a switchover to a low fat diet.


Ratios: n-6/n-3. Vegan diets are criticized for unfavorable n-6/n-3 fatty acid ratios. The criticism is valid but also applies to many other diets. Sample n-6/n-3 ratios, from Simopolous (2004):


·         Paleolithic period = 0.79

·         Current Japan = 4.00

·         Current United Kingdom and Northern Europe = 15.00

·         Current United States = 16.74

·         Current India, rural = 5–6.1

·         Current India, urban = 38–50


[Side remark: note the large difference between rural and urban India.]


Ratio implied by AIs? 


The ratio of the AIs suggested by Simopolous et al. (1999B) is 2:1, and the ratio:


(UL for LA)/(AI for ALA)


is 3:1, so overall these recommendations fall in the 2:1 – 4:1 range suggested above. Looking at the recommended worst case ratio (UL for LA)/(AI for ALA), we have total fat:


6.67 + 2.22 = 8.89 grams

8.89 grams * (9 calories/gram) = 80.01 calories = 4% of calories in 2000 calories/day diet.


The low value here - 4% of calories - provides some leeway in meeting the AIs on a low-fat diet, e.g., 10% fat by calories.


The Institute of Medicine AIs suggest an unfavorable ratio, e.g., the AIs for men are 17/1.6 = 10.63, which is better than the standard Western diet ratios reported for the US & UK, but still not good.


Let’s play with the numbers. How much ALA is needed for a 4:1 ratio when LA intake is 17 grams? Simple algebra yields:


17/4 = 4.25

17 grams LA + 4.25 grams ALA = 21.25 grams fat total

21.25 grams * (9 calories/gram) = 191.25 calories = 9.6% of calories in 2000 calories/day diet.


Thus meeting the Institute of Medicine AIs with a 4:1 ratio on a 10% fat diet is clearly problematic, but would be easier on diets that are 15+% fat by calories. Recall that the base of diets used to establish the Institute of Medicine AIs started at 15% fat and went up; a 10% fat by calories diet is outside this range,


The questions that remain to be answered here include:

·         Which set of AIs is better?

·         If low fat vegans adopt the Simopolous et al. (1999B) recommended AIs, will they also adopt the AIs for preformed EPA & DHA? (That would require supplementation.)

·         What should the AIs for EPA, DHA be?






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--Thomas E. (Tom) Billings

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