Vegetarian and Vegan Diets: Nutritional Disasters Part 1

Vegetarian Diet | The Paleo Diet

Over the years since the publication of my first book, I have been asked time and again if there is a vegetarian version of The Paleo Diet. I’ve got to say emphatically – No! Vegetarian diets are a bit of a moving target because they come in at least three major versions. We all know in principle that vegetarians do not eat meat, poultry or fish – this is the first and foremost characteristic of vegetarian diets. Less restrictive are lacto/ovo vegetarians who limit their animal food choices to dairy products and/or eggs, whereas vegans eat plant foods exclusively. A recent study published by Vegetarian Times Magazine revealed that 3.2% of U.S. adults or 7.3 million people follow a vegetarian-based diet.127 Approximately 0.5% or 1 million Americans are vegans. The study also indicated that over half (53%) of current vegetarians ate their plant based diet to improve overall health. Additional reasons underlying their vegetarian lifestyles were: 1) animal welfare cited by 54%, 2) environmental concerns named by 47%, 3) natural approaches to wellness mentioned by 39%, 4) food safety issues brought up by 31% and 5) weight loss and weight maintenance issues were cited by 25% of the respondents.127

First, let me say I respect everyone’s choice to eat whatever diet they like and those foods that they feel are best suited for themselves and their families. I also respect people’s decisions to abstain from eating meat for religious, moral, and ethical reasons. Nevertheless, as a scientist, I hope that we all try to make dietary decisions based not just upon philosophical and ethical issues, but also upon foods that are good for our bodies and long term health. Accordingly, I simply can’t lend my support to any version of vegetarian diets that people may adopt for the mistaken idea that these diets “improve overall health.”

Vegetarian Diets: The Evolutionary Evidence

Animal Food Subsistence | The Paleo DietAlthough vegetarianism has deep historical roots dating back at least to 500 BC with such ancient Greeks as Pythagoras, Porphyry and Plutarch,106, 115, 134 this manner of eating has only been with us for the mere blink of an eye on an evolutionary timescale. In our comprehensive analysis of 229 hunter-gatherer diets, my research group and I showed beyond question that no historically studied foragers were vegetarians.26 In fact, whenever and wherever animal foods were available they were always preferred over plant foods.26 The chart to the left shows the overwhelming preference for animal foods in all 229 hunter-gatherer societies that we studied. Notice that not a single foraging society fell into the (0 – 5%) animal subsistence category.

Most (73%) of the 229 hunter-gatherers consumed 46% or more of their daily energy as animal food.26 The compelling reason for their preference of animal foods over plant foods was because hunter-gatherers got more bang (food calories) for the buck (their energy expended to obtain the food), as verified by optimal foraging theory.

Human preference and appetite for meat, marrow and animal food has an incredibly long history in our ancestral line.18, 33 Fossils of butchered animals with stone tool-cut marks on their bones were discovered in Africa dating back 2.5 million years.33 These definitive “smoking guns” in the archaeological record leave little doubt that all human species ate animal foods from the very get-go of our existence. Scientists are able to determine the relative percentage of plant and animal food in extinct human (hominid) species by analyzing elements called isotopes within their fossilized bones.10, 104, 105 Every single hominid skeleton examined since the emergence of our own genus (Homo) 2.5 million years ago show an isotopic signature characteristic of meat based diets.10, 83, 104, 105, 124 Further, if we compare our biochemical and anatomical machinery to cats, who are absolute carnivores, we both share evolutionary enzyme pathways characteristic of processing lots of meat.27 If you are interested in these details, I have written about them in my debate with the noted vegetarian, Dr. T. Colin Campbell, author of The China Study.27Download the Full Debate Here

If we accept the idea that vegetarianism represents an ideal human diet, then this manner of eating must be part of a much larger or ultimate mechanism governing human biology. What I’m getting at is the question of “Why?” Why would a vegetarian diet, or for that matter, any diet represent an optimal nutritional road map for our species? Any unified theory of human nutrition is a detective story in which scientists attempt to reveal or uncover biological systems that have been designed by, and put into place by evolution through natural selection. Accordingly, hypotheses regarding what we should and shouldn’t eat must be consistent with the system and ancient environments that engineered our current genes. If we are to buy into vegetarianism, then the system, evolution via natural selection, which shaped our present genome necessarily had to be conditioned over eons by a plant based, vegetarian diet. Otherwise, there is no rationale alternative hypothesis to explain why humans would “prosper and thrive” on vegetarian diets.

As I have extensively pointed out,26, 27 there is no credible fossil, archeological, anthropological or biochemical evidence to show that any hunter-gatherers or pre-agricultural humans ever consumed all plant based diets. This information should be your first clue that there just may be some problems with vegetarian dietary recommendations created by humans for humans. What is that expression? “We are all human, we all make mistakes.” Let us not depend upon human frailties for dietary advice, but rather let us fall back on the wisdom of the system, again, evolution via natural selection, that designed the diet to which we are genetically adapted.

Vegetarian Diets: The Experimental Evidence

If you are considering adopting a vegetarian diet because you think it may improve your overall health and wellbeing, my immediate advice to you would be to forget it. I urge you to always let the data speak for itself, and don’t listen to me or anyone else until you have carefully scrutinized both sides of this or any other nutritional argument. I can guarantee you that the assessment of positive health effects, or lack thereof, caused by vegetarian diets is not just a straight forward matter involving objectivity and a mere sifting of scientific facts. Rather, this inquiry is politically charged involving charismatic individuals and well known scientists promoting a vegetarian viewpoint that is frequently at odds with the best science.

If you are currently a vegetarian or vegan, one of the most powerful health expectations for adopting this lifestyle is that you will outlive your “hamburger eating” neighbors by escaping cancer, 72 heart disease,69, 71 and all other causes of death (mortality).69, 71 In fact, if truth be told, your lifelong dietary deprivations will not prolong your lifespan, but rather will produce multiple nutrient deficiencies that are associated with numerous health problems and illnesses. If you have forced plant based diets upon your children, or unborn fetus they will also suffer. Not a pretty picture. Now let’s let the data speak for itself and get into the science of vegetarian diets and health.

In their 2009 Position Statement on Vegetarian Diets,28 The American Dietetic Association tells us,”…appropriately planned vegetarian diets, including total vegetarian or vegan diets are healthful, nutritionally adequate, and may provide health benefits in the prevention and treatment of certain disease. Well-planned vegetarian diets are appropriate for individuals during all stages of the life cycle, including pregnancy, lactation, infancy, childhood, and adolescence, and for athletes.” I don’t know what planet the authors of this paper came from or what scientific journals they have been reading, but these statements simply are not supported by the data.

To start with, if vegetarian diets are so healthful, then any reasonable person might expect that people eating plant based diets would have lower death rates from all causes than their meat eating counterparts. This question was never fully answered until 1999 when Dr. Key and colleagues at Oxford University conducted a large meta analysis comparing overall death rates between 27,808 vegetarians and 48,364 meat eaters.69 I quote Dr. Key’s study, “There were no significant differences between vegetarians and non-vegetarians in mortality from cerebrovascular disease, stomach cancer, colorectal cancer, lung cancer, breast cancer, prostate cancer or all other causes combined. I have underlined and bolded the last words of this sentence to emphasize the fact that vegetarians do not fair any better than their hamburger eating counterparts when death rates for all causes are considered. A more recent 2009 analysis (The EPIC-Oxford Study), employing the largest sample of vegetarians (33,883) ever examined came up with identical conclusions.71 I quote the authors, “Within the study mortality from circulatory diseases and all causes is not significantly different between vegetarians and meat eaters.” The results of this study71 and the earlier meta analysis,69 fly directly in the face of the American Dietetic Association’s suggestion that “vegetarian and vegan diets may provide health benefits in the prevention and treatment of certain disease.”28

Vegetarian Diets and Nutritional Deficiencies

The American Dietetic Association (ADA) advises us that, “…appropriately planned vegetarian diets, including total vegetarian or vegan diets are healthful and nutritionally adequate…28 This view is also shared by the USDA Choose My Plate guidelines which counsel us that, “Vegetarian diets can meet all the recommendations for nutrients.”142 The American Dietetic Association’s quote28 is a craftily written statement that is deliberately misleading and one sided. Taken at face value, it would appear that all vegetarian diets including vegan diets are nutritionally sound all by themselves and don’t require any additional nutritional supplements.

In order to get to the true meaning out of the ADA’s position statement, we need to dig deeper and determine what they mean by an “appropriately planned vegetarian diet.”  The ADA further hedges this statement by telling us that “…key nutrients for vegetarians include protein, n-3 fatty acids, iron, zinc, iodine, calcium, and vitamins D and B12.  A vegetarian diet can meet current recommendations for all of these nutrients.  In some cases, supplements or fortified foods can provide useful amounts of important nutrients.”28 Let’s dissect this masterly deceptive statement even further. The last line informing us that supplements and fortified foods “sometimes” are useful, is an outlandish understatement. In reality, it is not just in some cases that supplements and vitamin fortified foods are required, but rather in all cases for vegan diets and in most cases for lacto/ovo diets. Without supplementation vegetarian diets simply don’t work and invariably cause multiple nutrient deficiencies that not only adversely affect our health and wellbeing, but also that of our children.

Vegetarian Diets and Vitamin B12

Even informed vegetarians won’t argue that virtually all plant foods contain no vitamin B12 and that meat and animal foods are the only significant dietary source of this crucial nutrient. Additionally, we can’t synthesize B12 in our bodies. Consequently, if you decide to become a vegan, by default you will become vitamin B12 deficient unless you supplement your diet with this essential vitamin or eat B12 fortified foods.

Any lifelong dietary plan that requires nutrient supplementation on a regular basis makes no sense from an evolutionary perspective. You don’t have to be an evolutionary biologist to realize that wild animals don’t take nutritional supplements, nor do they normally develop vitamin deficiencies when living in their native environments. You will recall that not a single hunter-gatherer society consumed a vegetarian diet.26 This choice was not just a haphazard decision on their part, but rather was dictated by evolution through natural selection. If our ancestral foragers didn’t eat B12 containing animal foods, they developed vitamin B12 deficiencies which in turn impaired health and survival thereby worsening their chances of reproducing. Accordingly, any behavior that favored all plant diets would have been quickly weeded out by natural selection because of our genetic requirement for vitamin B12. Unlike modern day vegetarians, hunter-gatherers couldn’t simply pop a vitamin pill to make up for nutritional shortcomings in their diets. Without B12 supplementation, every hunter-gatherer who ever lived would have become vitamin B12 deficient if they didn’t eat animal food.

I want to emphasize that this flaw in nutritional logic is not just a minor point to be shuffled under the rug as the ADA28 and the USDA142 have done, but rather represents a colossal error in judgment for recommending vegan diets. To fully appreciate this massive breakdown in reasoning let’s examine the history of vitamin B12. Because it was the last vitamin to be discovered (1948), vitamin B12 only became available as a commercial supplement in the 1950s. Consequently, every person on the planet who consumed a strict lifelong vegan diet before B12’s discovery in 1948 would have been deficient in this critical nutrient. I wonder if the ADA28 and USDA142 would recommend vegan diets to U.S. citizens living prior to 1948 or only after 1948? This case in point shows how absurd their rationale for vegan diets appears – vegan diets are deadly before 1948 because they have no vitamin B12 but are “…healthful and nutritionally adequate…28 after 1948 because we can supplement this vitamin. OK – no big deal – nothing to get too excited about – just follow the ADA recommendations and make sure your vegetarian diet is “appropriately planned.”28 Right?

Unfortunately, most of the world’s vegetarians and vegans have not been able to figure out just exactly what an “appropriately planned28 vegetarian diet consists of, as almost all of them maintain deficient or marginal vitamin B12 concentrations in their bloodstreams. A 2003 study by Dr. Hermann and colleagues of 95 vegetarians revealed that 77% of lacto/ovo vegetarians were deficient in vitamin B12 whereas a staggering 92% of the vegans maintained deficiencies in this essential vitamin.52 The elegance of this study was that the researchers employed a powerful new procedure to precisely monitor vitamin B12 status in their subjects.50, 52 The simple measurement of vitamin B12 in the bloodstream often is misleading and doesn’t reflect true levels of B12 in our bodies.22, 64, 113 Nevertheless, a study (The EPIC-Oxford Study) which examined simple B12 concentrations in the blood of 231 ovo/lacto vegetarians and 232 vegans verified that B12 deficiencies were widespread within these groups.46 If we use the normal cutoff point (150 pmol/liter) as the measure for vitamin B12 deficiency in the blood, then the data from the EPIC-Oxford study shows that 73% of the vegans and 24% of the lacto/ovo vegetarians had vitamin B12 deficiencies.46 These two scientific papers are representative of nearly all other studies reporting vitamin B12 in vegetarians.1, 109, 118, 121 When this many people who follow vegetarian or vegan diets become vitamin B12 deficient, it is beyond comprehension to me why governmental agencies and national dietary organizations still stubbornly cling to the belief that plant based diets are healthful.

Even more disturbing is a report by Dr. Corinna Koebnick and co-workers in Germany showing that long term ovo/lacto vegetarian diets impair vitamin B12 status in pregnant women.74 The problem here is that maternal B12 deficiencies can then be handed down to the unborn fetus and to nursing infants who frequently have no other source of nutrition except for their mother’s vitamin B12 depleted milk.89, 107 B12 deficiency in pregnant women is not just a simple benign nutritional problem, but rather has potentially disastrous health outcomes for both mother and child. B12 deficiency in pregnant women is known to cause spontaneous abortions, weak labor, premature and low birth weight deliveries, birth defects, and the condition preeclampsia where mothers experience high blood pressure and damage to the liver, kidneys and blood vessels.7, 86, 87 Infants born from mothers with vitamin B12 deficiency frequently suffer from congenital malformations, irritability, failure to thrive, apathy, mental retardation and developmental problems.35 These data hardly support the ADA’s position that “Well-planned vegetarian diets are appropriate for individuals during all stages of the life cycle, including pregnancy, lactation, infancy, childhood….”28 In reality, the ADA’s recommendation of vegan and vegetarian diets “during all states of the life cycle28 is not only irresponsible, but in many cases is life threatening for mother, fetus and infant.

In Vegetarian and Vegan Diets: Nutritional Disasters Part 2, we’ll discuss why Vitamin B12 deficiencies are just as devastating to adults as they are to infants and expectant mothers.


Loren Cordain, Ph.D., Professor Emeritus


1. Alexander D, Ball MJ, Mann J. Nutrient intake and haematological status of vegetarians and age-sex matched omnivores. Eur J Clin Nutr. 1994 Aug;48(8):538-46.

2. Appleby P, Roddam A, Allen N, Key T. Comparative fracture risk in vegetarians and nonvegetarians in EPIC-Oxford. Eur J Clin Nutr. 2007 Dec;61(12):1400-6.

3. Appleton KM, Rogers PJ, Ness AR. Updated systematic review and meta-analysis of the effects of n-3 long-chain polyunsaturated fatty acids on depressed mood. Am J Clin Nutr. 2010 Mar;91(3):757-70

4. Baines M, Kredan MB, Davison A, Higgins G, West C, Fraser WD, Ranganath LR. The association between cysteine, bone turnover, and low bone mass. Calcif Tissue Int. 2007 Dec;81(6):450-4

5. Baines S, Powers J, Brown WJ. How does the health and well-being of young Australian vegetarian and semi-vegetarian women compare with non-vegetarians? Public Health Nutr. 2007 May;10(5):436-42.

6. Bhushan S, Pandey RC, Singh SP, Pandey DN, Seth P. Some observations on human semen analysis. Indian J Physiol Pharmacol. 1978 Oct-Dec;22(4):393-6.

7. Bennett M. Vitamin B12 deficiency, infertility and recurrent fetal loss. J Reprod Med. 2001 Mar;46(3):209-12.

8. Berker B, Kaya C, Aytac R, Satiroglu H. Homocysteine concentrations in follicular fluid are associated with poor oocyte and embryo qualities in polycystic ovary syndrome patients undergoing assisted reproduction. Hum Reprod. 2009 Sep;24(9):2293-302

9. Bissoli L, Di Francesco V, Ballarin A, Mandragona R, Trespidi R, Brocco G, Caruso B, Bosello O, Zamboni M. Effect of vegetarian diet on homocysteine levels. Ann Nutr Metab. 2002;46(2):73-9.

10. Bocherens H, Drucker DG, Billiou D, Patou-Mathis M, Vandermeersch B. Isotopic evidence for diet and subsistence pattern of the Saint-Cesaire I Neanderthal: review and use of a multi-source mixing model. J Hum Evol. 2005 Jul;49(1):71-87

11. Boivin J, Bunting L, Collins JA, Nygren KG. International estimates of infertility prevalence and treatment-seeking: potential need and demand for infertility medical care. Hum Reprod. 2007 Jun;22(6):1506-12.

12. Boxmeer JC, Smit M, Weber RF, Lindemans J, Romijn JC, Eijkemans MJ, Macklon NS, Steegers-Theunissen RP. Seminal plasma cobalamin significantly correlates with sperm concentration in men undergoing IVF or ICSI procedures. J Androl. 2007 Jul-Aug;28(4):521-7

13. Boxmeer JC, Brouns RM, Lindemans J, Steegers EA, Martini E, Macklon NS, Steegers-Theunissen RP. Preconception folic acid treatment affects the microenvironment of the maturing oocyte in humans. Fertil Steril. 2008 Jun;89(6):1766-70.

14. Boxmeer JC, Smit M, Utomo E, Romijn JC, Eijkemans MJ, Lindemans J, Laven JS, Macklon NS, Steegers EA, Steegers-Theunissen RP. Low folate in seminal plasma is associated with increased sperm DNA damage. Fertil Steril. 2009 Aug;92(2):548-56.

15. Brenna JT, Salem N Jr, Sinclair AJ, Cunnane SC. alpha-Linolenic acid supplementation and conversion to n-3 long-chain polyunsaturated fatty acids in humans. Prostaglandins Leukot Essent Fatty Acids. 2009 Feb-Mar;80(2-3):85-91.

16. Brown KH, Peerson JM, Baker SK, Hess SY. Preventive zinc supplementation among infants, preschoolers, and older prepubertal children. Food Nutr Bull. 2009 Mar;30(1 Suppl):S12-40.

17. Bucciarelli P, Martini G, Martinelli I, Ceccarelli E, Gennari L, Bader R, Valenti R, Franci B, Nuti R, Mannucci PM. The relationship between plasma homocysteine levels and bone mineral density in post-menopausal women. Eur J Intern Med. 2010 Aug;21(4):301-5

18. Bunn, HT, Kroll EM. Systematic butchery by Plio-Pleistocene hominids at Olduvai Gorge, Tanzania. Curr Anthropol 1986;20:365–398.

19. Calder PC, Yaqoob P. Omega-3 (n-3) fatty acids, cardiovascular disease and stability of atherosclerotic plaques. Cell Mol Biol (Noisy-le-grand). 2010 Feb 25;56(1):28-37.

20. Campbell-Brown M, Ward RJ, Haines AP, North WR, Abraham R, McFadyen IR, Turnlund JR, King JC. Zinc and copper in Asian pregnancies–is there evidence for a nutritional deficiency? Br J Obstet Gynaecol. 1985 Sep;92(9):875-85

21. Cappuccio FP, Bell R, Perry IJ, Gilg J, Ueland PM, Refsum H, Sagnella GA, Jeffery S, Cook DG. Homocysteine levels in men and women of different ethnic and cultural background living in England. Atherosclerosis. 2002 Sep;164(1):95-102.

22. Clarke R, Sherliker P, Hin H, Nexo E, Hvas AM, Schneede J, Birks J, Ueland PM, Emmens K, Scott JM, Molloy AM, Evans JG. Detection of vitamin B12 deficiency in older people by measuring vitamin B12 or the active fraction of vitamin B12, holotranscobalamin. Clin Chem. 2007 May;53(5):963-70

23. Clarke R. B-vitamins and prevention of dementia. Proc Nutr Soc. 2008 Feb;67(1):75-81.

24. Clarke R, Birks J, Nexo E, Ueland PM, Schneede J, Scott J, Molloy A, Evans JG. Low vitamin B-12 status and risk of cognitive decline in older adults. Am J Clin Nutr. 2007 Nov;86(5):1384-91.

25. Cogswell ME, Looker AC, Pfeiffer CM, Cook JD, Lacher DA, Beard JL, Lynch SR, Grummer-Strawn LM. Assessment of iron deficiency in US preschool children and nonpregnant females of childbearing age: National Health and Nutrition Examination Survey 2003-2006. Am J Clin Nutr. 2009 May;89(5):1334-42

26. Cordain L, Miller JB, Eaton SB, Mann N, Holt SH, Speth JD. Plant-animal subsistence ratios and macronutrient energy estimations in worldwide hunter-gatherer diets.Am J Clin Nutr. 2000 Mar;71(3):682-92.

27. Cordain L, Campbell TC. The protein debate. Catalyst Athletics, March 19, 2008.

28. Craig WJ, Mangels AR; American Dietetic Association. Position of the American Dietetic Association: vegetarian diets. J Am Diet Assoc. 2009 Jul;109(7):1266-82.

29. Crowe FL, Steur M, Allen NE, Appleby PN, Travis RC, Key TJ. Plasma concentrations of 25-hydroxyvitamin D in meat eaters, fish eaters, vegetarians and vegans: results from the EPIC-Oxford study. Public Health Nutr. 2011 Feb;14(2):340-6.

30. Dasarathy J, Gruca LL, Bennett C, Parimi PS, Duenas C, Marczewski S, Fierro JL, Kalhan SC. Methionine metabolism in human pregnancy. Am J Clin Nutr. 2010 Feb;91(2):357-65.

31. Davey GK, Spencer EA, Appleby PN, Allen NE, Knox KH, Key TJ. EPIC-Oxford: lifestyle characteristics and nutrient intakes in a cohort of 33 883 meat-eaters and 31 546 non meat-eaters in the UK. Public Health Nutr. 2003 May;6(3):259-69.

32. de Bortoli MC, Cozzolino SM. Zinc and selenium nutritional status in vegetarians. Biol Trace Elem Res. 2009 Mar;127(3):228-33.

33. de Heinzelin J, Clark JD, White T, Hart W, Renne P, WoldeGabriel G, Beyene Y, Vrba E. Environment and behavior of 2.5-million-year-old Bouri hominids. Science. 1999 Apr 23;284(5414):625-9

34. Dhonukshe-Rutten RA, van Dusseldorp M, Schneede J, de Groot LC, van Staveren WA. Low bone mineral density and bone mineral content are associated with low cobalamin status in adolescents. Eur J Nutr. 2005 Sep;44(6):341-7.

35. Dror DK, Allen LH. Effect of vitamin B12 deficiency on neurodevelopment in infants: current knowledge and possible mechanisms. Nutr Rev. 2008 May;66(5):250-5.

36. Ebisch IM, Peters WH, Thomas CM, Wetzels AM, Peer PG, Steegers-Theunissen RP. Homocysteine, glutathione and related thiols affect fertility parameters in the (sub)fertile couple. Hum Reprod. 2006 Jul;21(7):1725-33.

37. Ebisch IM, Pierik FH, DE Jong FH, Thomas CM, Steegers-Theunissen RP. Does folic acid and zinc sulphate intervention affect endocrine parameters and sperm characteristics in men? Int J Androl. 2006 Apr;29(2):339-45.

38. Elmadfa I, Singer I.Vitamin B-12 and homocysteine status among vegetarians: a global perspective. Am J Clin Nutr. 2009 May;89(5):1693S-1698S.

39. Falkingham M, Abdelhamid A, Curtis P, Fairweather-Tait S, Dye L, Hooper L.The effects of oral iron supplementation on cognition in older children and adults: a systematic review and meta-analysis. Nutr J. 2010 Jan 25;9:4.

40. Lightowler HJ, Davies GJ. Iodine intake and iodine deficiency in vegans as assessed by the duplicate-portion technique and urinary iodine excretion. Br J Nutr. 1998 Dec;80(6):529-35.

41. Fischer Walker CL, Ezzati M, Black RE. Global and regional child mortality and burden of disease attributable to zinc deficiency. Eur J Clin Nutr. 2009 May;63(5):591-7.

42. Food habits of a nation. In: The Hindu, August 14, 2006.

43. Fort P, Moses N, Fasano M, Goldberg T, Lifshitz F. Breast and soy-formula feedings in early infancy and the prevalence of autoimmune thyroid disease in children. J Am Coll Nutr. 1990 Apr;9(2):164-7.

44. Freeland-Graves JH, Ebangit ML, Hendrikson PJ. Alterations in zinc absorption and salivary sediment zinc after a lacto-ovo-vegetarian diet. Am J Clin Nutr. 1980 Aug;33(8):1757-66.

45. Freeland-Graves JH, Bodzy PW, Eppright MA. Zinc status of vegetarians. J Am Diet Assoc. 1980 Dec;77(6):655-61

46. Gilsing AM, Crowe FL, Lloyd-Wright Z, Sanders TA, Appleby PN, Allen NE, Key TJ. Serum concentrations of vitamin B12 and folate in British male omnivores, vegetarians and vegans: results from a cross-sectional analysis of the EPIC-Oxford cohort study. Eur J Clin Nutr. 2010 Sep;64(9):933-9

47. Hansen CM, Leklem JE, Miller LT. Vitamin B-6 status indicators decrease in women consuming a diet high in pyridoxine glucoside. J Nutr. 1996 Oct;126(10):2512-8

48. Harris WS, Kris-Etherton PM, Harris KA. Intakes of long-chain omega-3 fatty acid associated with reduced risk for death from coronary heart disease in healthy adults. Curr Atheroscler Rep. 2008 Dec;10(6):503-9.

49. Herbert V. Staging vitamin B-12 (cobalamin) status in vegetarians. Am J Clin Nutr. 1994 May;59(5 Suppl):1213S-1222S

50. Herrmann W, Obeid R, Schorr H, Geisel J. Functional vitamin B12 deficiency and determination of holotranscobalamin in populations at risk. Clin Chem Lab Med. 2003 Nov;41(11):1478-88.

51. Herrmann M, Widmann T, Colaianni G, Colucci S, Zallone A, Herrmann W. Increased osteoclast activity in the presence of increased homocysteine concentrations. Clin Chem. 2005 Dec;51(12):2348-53

52. Herrmann W, Schorr H, Obeid R, Geisel J. Vitamin B-12 status, particularly holotranscobalamin II and methylmalonic acid concentrations, and hyperhomocysteinemia in vegetarians. Am J Clin Nutr. 2003 Jul;78(1):131-6.

53. Herrmann M, Peter Schmidt J, Umanskaya N, Wagner A, Taban-Shomal O, Widmann T, Colaianni G, Wildemann B, Herrmann W. The role of hyperhomocysteinemia as well as folate, vitamin B(6) and B(12) deficiencies in osteoporosis: a systematic review. Clin Chem Lab Med. 2007;45(12):1621-32

54. Herrmann W, Obeid R, Schorr H, Hübner U, Geisel J, Sand-Hill M, Ali N, Herrmann M. Enhanced bone metabolism in vegetarians–the role of vitamin B12 deficiency. Clin Chem Lab Med. 2009;47(11):1381-7.

55. Heyland DK, Jones N, Cvijanovich NZ, Wong H. Zinc supplementation in critically ill patients: a key pharmaconutrient? JPEN J Parenter Enteral Nutr. 2008 Sep-Oct;32(5):509-19.

56. Hinton PS, Sinclair LM. Iron supplementation maintains ventilatory threshold and improves energetic efficiency in iron-deficient nonanemic athletes. Eur J Clin Nutr. 2007 Jan;61(1):30-9.

57. Hirwe R, Jathar VS, Desai S, Satoskar RS. Vitamin B12 and potential fertility in male lactovegetarians. J Biosoc Sci. 1976 Jul;8(3):221-7

58. Ho-Pham LT, Nguyen ND, Nguyen TV. Effect of vegetarian diets on bone mineral density: a Bayesian meta-analysis. Am J Clin Nutr. 2009 Oct;90(4):943-50.

59. Hotz C. Dietary indicators for assessing the adequacy of population zinc intakes. Food Nutr Bull. 2007 Sep;28(3 Suppl):S430-53.

60. Huang YC, Chang SJ, Chiu YT, Chang HH, Cheng CH. The status of plasma homocysteine and related B-vitamins in healthy young vegetarians and nonvegetarians. Eur J Nutr. 2003 Apr;42(2):84-90.

61. Humphrey LL, Fu R, Rogers K, Freeman M, Helfand M. Homocysteine level and coronary heart disease incidence: a systematic review and meta-analysis. Mayo Clin Proc. 2008 Nov;83(11):1203-12.

62. Hunt JR, Matthys LA, Johnson LK. Zinc absorption, mineral balance, and blood lipids in women consuming controlled lactoovovegetarian and omnivorous diets for 8 wk. Am J Clin Nutr. 1998 Mar;67(3):421-30.

63. Hunt JR, Roughead ZK. Nonheme-iron absorption, fecal ferritin excretion, and blood indexes of iron status in women consuming controlled lactoovovegetarian diets for 8 wk. Am J Clin Nutr. 1999 May;69(5):944-52

64. Hvas AM, Morkbak AL, Nexo E. Plasma holotranscobalamin compared with plasma cobalamins for assessment of vitamin B12 absorption; optimisation of a non-radioactive vitamin B12 absorption test (CobaSorb). Clin Chim Acta. 2007 Feb;376(1-2):150-4

65. Jathar VS, Hirwe R, Desai S, Satoskar RS. Dietetic habits and quality of semen in Indian subjects. Andrologia. 1976;8(4):355-8.

66. Jenkins DJ, Kendall CW, Connelly PW, Jackson CJ, Parker T, Faulkner D, Vidgen E. Effects of high- and low-isoflavone (phytoestrogen) soy foods on inflammatory biomarkers and proinflammatory cytokines in middle-aged men and women. Metabolism. 2002 Jul;51(7):919-24

67. Karabudak E, Kiziltan G, Cigerim N. A comparison of some of the cardiovascular risk factors in vegetarian and omnivorous Turkish females. J Hum Nutr Diet. 2008 Feb;21(1):13-22.

68. Katre P, Bhat D, Lubree H, Otiv S, Joshi S, Joglekar C, Rush E, Yajnik C. Vitamin B12 and folic acid supplementation and plasma total homocysteine concentrations in pregnant Indian women with low B12 and high folate status. Asia Pac J Clin Nutr. 2010;19(3):335-43.

69. Key TJ, Fraser GE, Thorogood M, Appleby PN, Beral V, Reeves G, Burr ML, Chang-Claude J, Frentzel-Beyme R, Kuzma JW, Mann J, McPherson K. Mortality in vegetarians and nonvegetarians: detailed findings from a collaborative analysis of 5 prospective studies. Am J Clin Nutr. 1999 Sep;70(3 Suppl):516S-524S.

70. Key TJ, Appleby PN, Rosell MS. Health effects of vegetarian and vegan diets. Proc Nutr Soc. 2006 Feb;65(1):35-41.

71. Key TJ, Appleby PN, Spencer EA, Travis RC, Roddam AW, Allen NE. Mortality in British vegetarians: results from the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford). Am J Clin Nutr. 2009 May;89(5):1613S-1619S

72. Key TJ, Appleby PN, Spencer EA, Travis RC, Roddam AW, Allen NE. Cancer incidence in vegetarians: results from the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford). Am J Clin Nutr. 2009 May;89(5):1620S-1626S

73. Khedr E, Hamed SA, Elbeih E, El-Shereef H, Ahmad Y, Ahmed S. Iron states and cognitive abilities in young adults: neuropsychological and neurophysiological assessment. Eur Arch Psychiatry Clin Neurosci. 2008 Dec;258(8):489-96. Epub 2008 Jun 20.

74. Koebnick C, Hoffmann I, Dagnelie PC, Heins UA, Wickramasinghe SN, Ratnayaka ID, Gruendel S, Lindemans J, Leitzmann C. Long-term ovo-lacto vegetarian diet impairs vitamin B-12 status in pregnant women. J Nutr. 2004 Dec;134(12):3319-26.

75. Knovich MA, Storey JA, Coffman LG, Torti SV, Torti FM. Ferritin for the clinician. Blood Rev. 2009 May;23(3):95-104

76. Kornsteiner M, Singer I, Elmadfa I. Very low n-3 long-chain polyunsaturated fatty acid status in Austrian vegetarians and vegans. Ann Nutr Metab. 2008;52(1):37-47

77. Krajcovicová-Kudlácková M, Bucková K, Klimes I, Seboková E. Iodine deficiency in vegetarians and vegans. Ann Nutr Metab. 2003;47(5):183-5.

78. Krivosíková Z, Krajcovicová-Kudlácková M, Spustová V, Stefíková K, Valachovicová M, Blazícek P, Nĕmcová T. The association between high plasma homocysteine levels and lower bone mineral density in Slovak women: the impact of vegetarian diet. Eur J Nutr. 2010 Apr;49(3):147-53

79. Kumar J, Garg G, Sundaramoorthy E, Prasad PV, Karthikeyan G, Ramakrishnan L, Ghosh S, Sengupta S. Vitamin B12 deficiency is associated with coronary artery disease in an Indian population. Clin Chem Lab Med. 2009;47(3):334-8.

80. Laidlaw SA, Grosvenor M, Kopple JD. The taurine content of common foodstuffs. JPEN J Parenter Enteral Nutr. 1990 Mar-Apr;14(2):183-8.

81. Laidlaw SA, Shultz TD, Cecchino JT, Kopple JD. Plasma and urine taurine levels in vegans. Am J Clin Nutr. 1988 Apr;47(4):660-3

82. Leboff MS, Narweker R, LaCroix A, Wu L, Jackson R, Lee J, Bauer DC, Cauley J, Kooperberg C, Lewis C, Thomas AM, Cummings S. Homocysteine levels and risk of hip fracture in postmenopausal women. J Clin Endocrinol Metab. 2009 Apr;94(4):1207-13

83. Lee-Thorp J, Thackeray JF, van der Merwe N. The hunters and the hunted revisited. J Hum Evol 2000; 39: 565–576.

84. Lin PY, Huang SY, Su KP. A meta-analytic review of polyunsaturated fatty acid compositions in patients with depression. Biol Psychiatry. 2010 Jul 15;68(2):140-7.

85. Mezzano D, Kosiel K, Martínez C, Cuevas A, Panes O, Aranda E, Strobel P, Pérez DD, Pereira J, Rozowski J, Leighton F. Cardiovascular risk factors in vegetarians. Normalization of hyperhomocysteinemia with vitamin B(12) and reduction of platelet aggregation with n-3 fatty acids. Thromb Res. 2000 Nov 1;100(3):153-60.

86. Molloy AM, Kirke PN, Brody LC, Scott JM, Mills JL. Effects of folate and vitamin B12 deficiencies during pregnancy on fetal, infant, and child development. Food Nutr Bull. 2008 Jun;29(2 Suppl):S101-11

87. Molloy AM, Kirke PN, Troendle JF, Burke H, Sutton M, Brody LC, Scott JM, Mills JL. Maternal vitamin B12 status and risk of neural tube defects in a population with high neural tube defect prevalence and no folic Acid fortification. Pediatrics. 2009 Mar;123(3):917-23.

88. Mann N, Pirotta Y, O’Connell S, Li D, Kelly F, Sinclair A. Fatty acid composition of habitual omnivore and vegetarian diets. Lipids. 2006 Jul;41(7):637-46

89. Mariani A, Chalies S, Jeziorski E, Ludwig C, Lalande M, Rodière M. [Consequences of exclusive breast-feeding in vegan mother newborn–case report]. Arch Pediatr. 2009 Nov;16(11):1461-3.

90. McCann JC, Ames BN. An overview of evidence for a causal relation between iron deficiency during development and deficits in cognitive or behavioral function. Am J Clin Nutr. 2007 Apr;85(4):931-45.

91. McCarty MF. Sub-optimal taurine status may promote platelet hyperaggregability in vegetarians.Med Hypotheses. 2004;63(3):426-33.

92. McClung JP, Karl JP, Cable SJ, Williams KW, Nindl BC, Young AJ, Lieberman HR. Randomized, double-blind, placebo-controlled trial of iron supplementation in female soldiers during military training: effects on iron status, physical performance, and mood. Am J Clin Nutr. 2009 Jul;90(1):124-31.

93. Michie CA, Chambers J, Abramsky L, Kooner JS. Folate deficiency, neural tube defects, and cardiac disease in UK Indians and Pakistanis. Lancet. 1998 Apr 11;351(9109):1105.

94. Misra A, Vikram NK, Pandey RM, Dwivedi M, Ahmad FU, Luthra K, Jain K, Khanna N, Devi JR, Sharma R, Guleria R. Hyperhomocysteinemia, and low intakes of folic acid and vitamin B12 in urban North India. Eur J Nutr. 2002 Apr;41(2):68-77.

95. Messina M, Redmond G. Effects of soy protein and soybean isoflavones on thyroid function in healthy adults and hypothyroid patients: a review of the relevant literature. Thyroid. 2006 Mar;16(3):249-58.

96. Osendarp SJ, Murray-Kolb LE, Black MM. Case study on iron in mental development–in memory of John Beard (1947-2009). Nutr Rev. 2010 Nov;68 Suppl 1:S48-52. doi: 10.1111/j.1753-4887.2010.00331.x.

97. Plourde M, Cunnane SC. Extremely limited synthesis of long chain polyunsaturates in adults: implications for their dietary essentiality and use as supplements. Appl Physiol Nutr Metab. 2007 Aug;32(4):619-34.

98. Pront R, Margalioth EJ, Green R, Eldar-Geva T, Maimoni Z, Zimran A, Elstein D. Prevalence of low serum cobalamin in infertile couples. Andrologia. 2009 Feb;41(1):46-50.

99. Proudman SM, Cleland LG, James MJ. Dietary omega-3 fats for treatment of inflammatory joint disease: efficacy and utility. Rheum Dis Clin North Am. 2008 May;34(2):469-79.

100. Rana SK, Sanders TA. Taurine concentrations in the diet, plasma, urine and breast milk of vegans compared with omnivores. Br J Nutr. 1986 Jul;56(1):17-27.

101. Refsum H, Yajnik CS, Gadkari M, Schneede J, Vollset SE, Orning L, Guttormsen AB, Joglekar A, Sayyad MG, Ulvik A, Ueland PM. Hyperhomocysteinemia and elevated methylmalonic acid indicate a high prevalence of cobalamin deficiency in Asian Indians. Am J Clin Nutr. 2001 Aug;74(2):233-41.

102. Remer T, Neubert A, Manz F. Increased risk of iodine deficiency with vegetarian nutrition. Br J Nutr. 1999 Jan;81(1):45-9.

103. Reynolds RD: Bioavailability of vitamin B-6 from plant foods. Am J Clin Nutr 1988;48:863-67.

104. Richards MP, Pettitt PB, Trinkaus E, Smith FH, Paunovic M, Karavanic, I. Neanderthal diet at Vindija and Neanderthal predation: The evidence from stable isotopes. Proc Natl Acad Sci 2000;97: 7663–7666.

105. Richards MP, Hedges REM, Jacobi R, Current, A, Stringer C. Focus: Gough’s Cave and Sun Hole Cave human stable isotope values indicate a high animal protein diet in the British Upper Palaeolithic. J Archaeol Sci 2000;27: 1–3.

106. Roe DA. History of promotion of vegetable cereal diets. J Nutr 1986;116:1355-1363.

107. Roed C, Skovby F, Lund AM. Severe vitamin B12 deficiency in infants breastfed by vegans]. Ugeskr Laeger. 2009 Oct 19;171(43):3099-101

108. Rosell MS, Lloyd-Wright Z, Appleby PN, Sanders TA, Allen NE, Key TJ. Long-chain n-3 polyunsaturated fatty acids in plasma in British meat-eating, vegetarian, and vegan men. Am J Clin Nutr. 2005 Aug;82(2):327-34.

109. Rush EC, Chhichhia P, Hinckson E, Nabiryo C. Dietary patterns and vitamin B(12) status of migrant Indian preadolescent girls. Eur J Clin Nutr. 2009 Apr;63(4):585-7. Epub 2007 Dec 19.

110. Sanders TA, Roshanai F. Platelet phospholipid fatty acid composition and function in vegans compared with age- and sex-matched omnivore controls. Eur J Clin Nutr. 1992 Nov;46(11):823-31.

111. Sanders TA. DHA status of vegetarians. Prostaglandins Leukot Essent Fatty Acids. 2009 Aug-Sep;81(2-3):137-41.

112. Sato Y, Honda Y, Iwamoto J, Kanoko T, Satoh K. Effect of folate and mecobalamin on hip fractures in patients with stroke: a randomized controlled trial. JAMA. 2005 Mar 2;293(9):1082-8.

113. Schneede J, Ueland PM. Novel and established markers of cobalamin deficiency: complementary or exclusive diagnostic strategies. Semin Vasc Med. 2005 May;5(2):140-55

114. Selhub J, Morris MS, Jacques PF. In vitamin B12 deficiency, higher serum folate is associated with increased total homocysteine and methylmalonic acid concentrations. Proc Natl Acad Sci U S A. 2007 Dec 11;104(50):19995-20000.

115. Shapin S. Vegetable love: the history of vegetarianism. New Yorker. 2007 Jan 22:80-4.

116. Singh K, Singh SK, Sah R, Singh I, Raman R. Mutation C677T in the methylenetetrahydrofolate reductase gene is associated with male infertility in an Indian population. Int J Androl. 2005 Apr;28(2):115-9.

117. Srikumar TS, Johansson GK, Ockerman PA, Gustafsson JA, Akesson B. Trace element status in healthy subjects switching from a mixed to a lactovegetarian diet for 12 mo. Am J Clin Nutr. 1992 Apr;55(4):885-90.

118. Stabler SP, Allen RH. Vitamin B12 deficiency as a worldwide problem. Annu Rev Nutr. 2004;24:299-326

119. Stephen EH, Chandra A. Declining estimates of infertility in the United States: 1982-2002. Fertil Steril. 2006 Sep;86(3):516-23.

120. Szymanski KM, Wheeler DC, Mucci LA. Fish consumption and prostate cancer risk: a review and meta-analysis. Am J Clin Nutr. 2010 Nov;92(5):1223-33.

121. Taneja S, Bhandari N, Strand TA, Sommerfelt H, Refsum H, Ueland PM, Schneede J, Bahl R, Bhan MK. Cobalamin and folate status in infants and young children in a low-to-middle income community in India. Am J Clin Nutr. 2007 Nov;86(5):1302-9.

122. te Velde E, Burdorf A, Nieschlag E, Eijkemans R, Kremer JA, Roeleveld N, Habbema D.
Is human fecundity declining in Western countries? Hum Reprod. 2010 Jun;25(6):1348-53.

123. Tikkiwal M, Ajmera RL, Mathur NK. Effect of zinc administration on seminal zinc and fertility of oligospermic males. Indian J Physiol Pharmacol. 1987 Jan-Mar;31(1):30-4.

124. van der Merwe NJ, Thackeray JF, Lee-Thorp JA, Luyt J. The carbon isotope ecology and diet of Australopithecus africanus at Sterkfontein, South Africa J Hum Evol 2003;44: 581–597.

125. van Meurs JB, Dhonukshe-Rutten RA, Pluijm SM, van der Klift M, de Jonge R, Lindemans J, de Groot LC, Hofman A, Witteman JC, van Leeuwen JP, Breteler MM, Lips P, Pols HA, Uitterlinden AG. Homocysteine levels and the risk of osteoporotic fracture. N Engl J Med. 2004 May 13;350(20):2033-41.

126. van Mil NH, Oosterbaan AM, Steegers-Theunissen RP. Teratogenicity and underlying mechanisms of homocysteine in animal models: a review. Reprod Toxicol. 2010 Dec;30(4):520-31.

127. Vegetarianism in American. Vegetarian Times Magazine, 2008.

128. Verkleij-Hagoort AC, Verlinde M, Ursem NT, Lindemans J, Helbing WA, Ottenkamp J, Siebel FM, Gittenberger-de Groot AC, de Jonge R, Bartelings MM, Steegers EA, Steegers-Theunissen RP. Maternal hyperhomocysteinaemia is a risk factor for congenital heart disease. BJOG. 2006 Dec;113(12):1412-8.

129. Vogel T, Dali-Youcef N, Kaltenbach G, Andrès E. Homocysteine, vitamin B12, folate and cognitive functions: a systematic and critical review of the literature. Int J Clin Pract. 2009 Jul;63(7):1061-7

130. Wald DS, Law M, Morris JK. Homocysteine and cardiovascular disease: evidence on causality from a meta-analysis. BMJ. 2002 Nov 23;325(7374):1202.

131. Waldmann A, Dörr B, Koschizke JW, Leitzmann C, Hahn A. Dietary intake of vitamin B6 and concentration of vitamin B6 in blood samples of German vegans. Public Health Nutr. 2006 Sep;9(6):779-84.

132. Wang Q, Yu LG, Campbell BJ, Milton JD, Rhodes JM. Identification of intact peanut lectin in peripheral venous blood. Lancet. 1998;352:1831-2

133. Werder SF. Cobalamin deficiency, hyperhomocysteinemia, and dementia. Neuropsychiatr Dis Treat. 2010 May 6;6:159-95

134. Whorton JC. Historical development of vegetarianism. Am J Clin Nutr 1994;59 (suppl) 1103S-9S.

135. Wilson AK, Ball MJ. Nutrient intake and iron status of Australian male vegetarians. Eur J Clin Nutr. 1999 Mar;53(3):189-94.

136. Wong WY, Merkus HM, Thomas CM, Menkveld R, Zielhuis GA, Steegers-Theunissen RP. Effects of folic acid and zinc sulfate on male factor subfertility: a double-blind, randomized, placebo-controlled trial. Fertil Steril. 2002 Mar;77(3):491-8.

137. Xavier D, Pais P, Devereaux PJ, Xie C, Prabhakaran D, Reddy KS, Gupta R, Joshi P, Kerkar P, Thanikachalam S, Haridas KK, Jaison TM, Naik S, Maity AK, Yusuf S; CREATE registry investigators. Treatment and outcomes of acute coronary syndromes in India (CREATE): a prospective analysis of registry data. Lancet. 2008 Apr 26;371(9622):1435-42.

138. Zhao YT, Chen Q, Sun YX, Li XB, Zhang P, Xu Y, Guo JH. Prevention of sudden cardiac death with omega-3 fatty acids in patients with coronary heart disease: a meta-analysis of randomized controlled trials. Ann Med. 2009;41(4):301-10.

139. Zhao JH, Sun SJ, Horiguchi H, Arao Y, Kanamori N, Kikuchi A, Oguma E, Kayama F.
A soy diet accelerates renal damage in autoimmune MRL/Mp-lpr/lpr mice. Int Immunopharmacol. 2005 Oct;5(11):1601-10.

140. Zimmermann MB. Iodine deficiency. Endocr Rev. 2009 Jun;30(4):376-408

141. Zimmermann MB. The adverse effects of mild-to-moderate iodine deficiency during pregnancy and childhood: a review. Thyroid. 2007 Sep;17(9):829-35.

142. United States Department of Agriculture (USDA). Choose My Plate. gov. Tips for Vegetarians,

143. Micha R, Mozaffarian D. Saturated fat and cardiometabolic risk factors, coronary heart disease, stroke, and diabetes: a fresh look at the evidence. Lipids. 2010 Oct;45(10):893-905.

144. Siri-Tarino PW1, Sun Q, Hu FB, Krauss RM. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Am J Clin Nutr. 2010 Mar;91(3):535-46.

145. Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Saturated fatty acids and risk of coronary heart disease: modulation by replacement nutrients. Curr Atheroscler Rep. 2010 Nov;12(6):384-90.

146. Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Saturated fat, carbohydrate, and cardiovascular disease. Am J Clin Nutr. 2010 Mar;91(3):502-9

147. Pirke KM, Schweiger U, Laessle R, Dickhaut B, Schweiger M, Waechtler M. Dieting influences the menstrual cycle: vegetarian versus nonvegetarian diet. Fertil Steril. 1986 Dec;46(6):1083-8.

148. Cordain L. Cereal grains: humanity’s double-edged sword. World Rev Nutr Diet. 1999;84:19-73.

149. Rall LC, Meydani SN. Vitamin B6 and immune competence. Nutr Rev. 1993 Aug;51(8):217-25.

150. Folstein M, Liu T, Peter I, Buell J, Arsenault L, Scott T, Qiu WW.The homocysteine hypothesis of depression. Am J Psychiatry. 2007 Jun;164(6):861-7.

151. Zhang XH, Ma J, Smith-Warner SA, Lee JE, Giovannucci E. Vitamin B6 and colorectal cancer: current evidence and future directions. World J Gastroenterol. 2013 Feb 21;19(7):1005-10

152. Bougma K1, Aboud FE, Harding KB, Marquis GS. Iodine and mental development of children 5 years old and under: a systematic review and meta-analysis. Nutrients. 2013 Apr 22;5(4):1384-416.

153. Zimmermann MB. The effects of iodine deficiency in pregnancy and infancy. Paediatr Perinat Epidemiol. 2012 Jul;26 Suppl 1:108-17

About Loren Cordain, PhD, Professor Emeritus

Loren Cordain, PhD, Professor EmeritusDr. Loren Cordain is Professor Emeritus of the Department of Health and Exercise Science at Colorado State University in Fort Collins, Colorado. His research emphasis over the past 20 years has focused upon the evolutionary and anthropological basis for diet, health and well being in modern humans. Dr. Cordain’s scientific publications have examined the nutritional characteristics of worldwide hunter-gatherer diets as well as the nutrient composition of wild plant and animal foods consumed by foraging humans. He is the world’s leading expert on Paleolithic diets and has lectured extensively on the Paleolithic nutrition worldwide. Dr. Cordain is the author of six popular bestselling books including The Real Paleo Diet Cookbook, The Paleo Diet, The Paleo Answer, and The Paleo Diet Cookbook, summarizing his research findings.

Comments to this website are moderated by our editorial board. For approval, comments need to be relevant to the article and free of profanities and personal attacks. We encourage cordial debates for the betterment of understanding and discovery. Comments that advertise or promote a business will also not be approved, however, links to relevant blog posts that follow the aforementioned criteria will be allowed. Thank you.

“41” Comments

  1. Pingback: Vegan Diet Versus Paleo Diet | My Good Health lost

  2. I have been listening to your talk on the Diet Doctor You Tube video. Thanks so much! I have been vegetarian for 26 years. I was put on the vegetarian diet for my juvenile rheumatoid arthritis which I have had for more thank 30 years. At that time I was almost emaciated as my body was not absorbing nutrients from my food. On the advice of a chiropractor I became vegetarian. Becoming vegetarian really helped with inflammation. I stopped having joint pain and swelling. It was amazing. I recently had a nuclear stress test to take a look at my heart. No damage to my heart was detected. However about 10 years ago I developed a systemic candida problem which I cannot seem to clear up. About 8 years ago I began having psychiatric problems. I also found out that I have Celiac Disease which was apparently causing the first problem of emaciation. Failure to thrive is a symptom of Celiac Disease. I also found out 8 years ago that I have Pyroluria. That is the cause of my psychiatric problems. I began taking a vitamin regime for the Pyroluria and my life changed dramatically. That lasted about 5 years. In recently years the vitamin regime no longer helps. I definitely have a severed zinc deficiency as my teeth are way over crowed and my the roof of my mouth has narrowed dramatically. My waistline has grown. I have severe bloating. My skin is sagging. I have thyroid disease and allergies to everything it seems. Reading your blog and listening to you on You Tube has helped me to understand how much of my health issues can be attributed to my vegetarian diet. Thanks for this information!

    • Rita,

      We wish you luck following an ancestral eating plan to correct your health problems. Consider consuming oysters more regularly to get your zinc levels back up. Red meat is rich in zinc and iron as well. Also, you should consider consuming grass fed beef liver to correct any sort of nutrient deficiencies you may have.

  3. Taking a B12 supplement seems a lot more sustainable than raising billions of animals to slaughter year after year while climate change is disrupting nations and there are millions of people starving

  4. I’d like to start by saying that the writer of this article clearly has an agenda. I am not a vegan but have significantly lowered my dependence on animal products, and almost never eat dairy. Mainly because of stomach issues. My doctor gave me every possible test available to me in Canada and could not diagnose any stomach problems. According to western medicine I did not have a problem. I was on a paleo diet for over a year and felt a bit better, but still had to skip dinner to make sure that I slept without indigestion. I tried a whole plant based diet for a month and watched all of my health problems disappear. That being said I still eat meat once every couple of weeks, mainly because I like it. I have never had so much energy or slept so well in my entire life!

    I think the key take away from the comments is that there is no one answer for everyone. There are a lot of extreme views on diets. Everyone’s body is different. Our western diets have a much heavier dependence on meat products than our bodies actually need. I’m not a doctor, but i’m pretty sure hunter gatherers didn’t eat meat 3 times a day, with our modern preservation techniques, and cooking methods…again, i’m not a doctor. I also think it is ignorant to compare hunter and gatherer eating habits to todays eating habits. Hunter gatherers didn’t have access to any food in any season from anywhere in the world like we have today. They were limited to their local resources which limited them in availability and diversity of food. They also had much shorter life spans and poorer qualities of life…so why is this even coming up?

    Eating a whole plant based diet is a challenge, but forces you to understand what all of your options are so that you get the nutrition that you need. Also, I believe the comments on B12 are inaccurate from my research. I also avoid soy at all cost.

  5. I looked up “The Oxford Vegetarian Study” done by Dr. Keys here:

    The abstract states that there was actually a reduced mortality rate in non-meat eaters. Here it is:

    “After adjusting for smoking, body mass index, and social class, death rates were lower in non-meat-eaters than in meat eaters for each of the mortality endpoints studied [relative risks and 95% CIs: 0.80 (0.65, 0.99) for all causes of death, 0.72 (0.47, 1.10) for ischemic heart disease, and 0.61 (0.44, 0.84) for all malignant neoplasms]. Mortality from ischemic heart disease was also positively associated with estimated intakes of total animal fat, saturated animal fat, and dietary cholesterol. Other analyses showed that non-meat-eaters had only half the risk of meat eaters of requiring an emergency appendectomy, and that vegans in Britain may be at risk for iodine deficiency. Thus, the health of vegetarians in this study is generally good and compares favorably with that of the nonvegetarian control subjects. Larger studies are needed to examine rates of specific cancers and other diseases among vegetarians.”

  6. Pingback: Vegetarian Paleo Diet | Adventist Vegetarian Diabetics

  7. I’d just like to say that you say throughout the article that you will ‘let the data speak for itself’ before going on to provide your own interpretation of the data.

    I am certain that being a scientist you realise that data is never neutral. It has always been collected by someone with a partiocular agenda for example for the purposes of proving or disproving a hypothesis or becasue the reearch has been funded by a commercial organisation with a particular aim.

    I think that the way you have written this article could be misleading, as I am sure that a lot of the same data could be used by someone else to support the opposing argument!

    People should, as you say, independently review the literature on the topic if they want to make an informed choice, rather than accept your arguments.

    I am a vegetarian and have been so since I was about 11 years old and like a lot of people who a veggie or vegan for moral reasons I wouldn’t change my diet based on science, although I would (and have) ensure that I modify it to try to get the bes possible balance of nutrients as I don’t dispute there are things I’m probably missing out on.

    But then I’m sure a lot of people who eat meat are missing out on important nutrients from other protein sources, or not eating enough fruit, veg and nuts.

    Diet fads and crazes are all very well, but I prefer to make sure my diet is varied (i.e. lots of fresh fruit & veg, differnet sources of protein – pulses, cheese, nuts, seeds), and that I eat very few processed foods and ‘meat replacements’ (e.g. Quorn) and also try to exercise and keep generally healthy. This probably has more to do with my overall health (which is good) and my weight (I’ve alwas been slim) than whether I eat meat or not.

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  26. I saw a few comments where people mention that after stop eating meat they became tired, sick etc. Well I’m only assuming then that you people were not eating the right stuff. You can’t just swap from eating meat to not eating meat at all. The secret is, firstly to stop eating flesh slowly, reducing the amount and start introducing more greens, seeds, nuts and fruits to the diet. And mainly try to do some research or talk to people who are vegans/vegetarians for a long time and ask what their diets are. That’s what I did. I’ve been a vegetarian for a bit over 2 years now and I’ve lost weight, have more energy than never before and rarely get sick. I do blood tests every 6 months and never had any iron deficiency or any other problem. I’m the healthiest Ive ever been and also very fit. I’m slowly introducing it to my bf, who loves meat but since I’ve been cooking for him and making more seafood and less red meat, he keeps telling me how healthy he feels and how much he used to get sick before and now never gets either. So, as I said before, it all comes to what your diet is and what you’re putting inside your body. Meat is very heavy so the body takes a while to digest it, making people more tired and fatigue. The text also referred to our ancestors, but let’s not forget that they were HUNTERS and the meat was free from hormones and preservatives back those days, while nowadays it’s just full of crap and it is also the cause of cancer in the majority of the population together with milk.

  27. Thanks so much for your honest and well-researched post. I am a nutritionist myself, and I know that diet and food can be a very intense subject for people. I was a vegetarian for about 7 years and it was not a wise choice for me. I had more panic and anxiety attacks and heart palpitations when I was vegetarian than I do now. Today, I eat a very balanced, nourishing diet that is centered around grass-fed fats, meats, raw dairy, fermented foods, bone broth and organic veggies. Thanks again for sharing this informative article.

    • I am a Doctor of Chinese medicine. In Chinese Medicine, red meat is a major food source for building blood. Blood deficiency leads to symptoms like anxiety, palpitations, difficult concentrating and difficulty sleeping. Unfortunately, not eating meat makes people prone to blood deficiency and these types of problems. If you don’t eat meat, you need to eat a lot of other blood building foods like red kidney beans, dark fruits like cherries and plums, dark veggies like beetroot and carrots and wheat.

  28. Pingback: Paleo Kosher, Paleo Halal, and Other Religious Dietary Restrictions | Health Fitness Daily


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  33. Pingback: Can We Ward Off Anemia with The Paleo Diet? | Dr. Cordain : The Paleo Diet™

  34. I like the taste and moisture of vegetables and over the years have reduced the amount of red meant I consume.
    The comments are very enlightening, and thanks to everyone who took the time to weigh in!

  35. Hello,

    I’ve read this article, along with many other articles related to the topic “to be or not to be a vegan”. And I would like to tel you my story.

    I was born in a family of farmers in Europe and grew up with a (roughly) 50/50 diet (meat/veggies). Because of moral reasons I tried becoming a vegan. I asked my husband to help me along the way, too. This is what happened:

    When I decided to slowly eliminate animal products from my diet, I was of average weight, exercising regularly due to my job and eating an omnivore diet.

    In 2-3 months I became 100% vegan. I’ve made my research of what a “balanced vegan diet” means and tried my best. But. After keeping this vegetarian diet for 6 months, both my husband and I have realized some changes:
    – I lost a lot of weight, but not belly fat, rather muscle mass. As we live in Japan and many of my meals are made of some sort of soy product, I don’t think it was proteins I lacked, but then, who knows…
    – I became more fatigued and got tired really easily;
    – I had started having really bad cravings, which took a toll on my psyche;
    – I suffered from constipation – what used to work in the past to reduce constipation, has stopped working, to the point that I started to produce the same kind of human waste as… a goat… :)
    – I became anemic. Pam pam! From this point I completely stopped being 100% vegan.

    I started to slowly re-introduce fish, milk, cheese and eggs in my diet, and the occasional chicken meat, and now, after more than 8 months since I’ve returned to an omnivorous diet, I feel waay better, more active, healthier and the tests came out great.

    What I want to say is that, while for some people becoming or being vegans is something which brings great benefits, for others it might not be a good idea after all…

    Just as a note, the Okinawan people, who are the population with the most centenarians in the world, eat a lot of soy, vegetables and mushrooms, seaweed, but also a lot of seafood and chicken meat!

    And among the world’s most successful athletes, how many of them are pure vegans?

    All in all, be it a vegan diet, paleo diet or any other diet, I think the best thing to do is eat whatever you feel brings you the most benefits, without over-eating and with having plenty of exercise.

    For me, balance is the secret. So good luck everybody! Try all sorts of diets and see which one helps you feel better and keep it up by being balanced and active! Cheers!

  36. Pingback: Food Ethics and Anthropology | Winston's Journal

  37. B12 can be obtained in nearly all fortified foods these days, from soy and almond milk to protein and energy bars. It doesn’t come from meat; it comes from the dirt that animals eat when consuming their food.

    As always, articles like this one try to use science to push something that’s no more than an opinion without considering actual facts or scenarios.

    • The key word your using is FORTIFIED. That means it had to be added to the food substance. The point being made is vegetarian diets are not nutritious without supplementation, not to mention despite all these fortified foods the studies still showed B12 deficiency in vegetarians/vegans. Did you read the article or just skim through it?

  38. Wow. You write very well with all of your quotes and your 153 references but saying a vegan/vegetarian lifestyle isn’t a wise choice is just ludicrous. While I agree that B12 is hard to get as a vegan/vegetarian, it’s actually not as impossible as you make it out to be. The best thing anyone following a plant-based diet can do is EDUCATE themselves! Like most anything in life, the more we know, the better we can do it. I urge everyone who has read your post, to not stop here and take it all word for word. Your ideas are quite narrow minded. As is your right of course.

  39. First off, let me say I am not a vegetarian and since I love eating meat I don’t plan to become a vegetarian – even though I see the ethical argument in favor of this diet.
    Having put the ethics and all aside, my focus is on health. Here Cordain cites a study (69, Key et al: which states “There were no significant differences between vegetarians and non-vegetarians in mortality from cerebrovascular disease, stomach cancer, colorectal cancer, lung cancer, breast cancer, prostate cancer or all other causes combined.”
    However, the exact same study says a few sentences before that: “Mortality from ischemic heart disease was 24% lower in vegetarians than in nonvegetarians.” Given that ischemic heart disease is the most common cause of death in Western societies, this is a fact that is not minor. To me as a carnivore, the message would be as follows: Carnivore and vegatarian diets hold the same health benefits, except that the vegetarian diet significantly reduces your chances of dying from the Nr. 1 cause of death, namely heart disease. For me this sounds like eating vegetarian is the safer bet?

    • The cardiovascular disease rates in the US are not caused by being meat eaters though, which is the point you are missing. It’s because Americans eat bags of chips (which don’t contain any meat), french fries (again no meat), soda (meat free!), huge amounts of processed high fat carbohydrates like donuts and other baked goods (meat free again) and I could go on and on. Eating a balanced diet low in processed food and includes lean meats is healthy. And, sugar is the real cause of most of the cardiovascular issues as new study after study is revealing. The average Western diet is high in sugar.

  40. It’s unfair to say that a vegetarian diet is harmful to a growing fetus. There are many people in India who follow all vegetarian diets for their whole lives, including while pregnant and give birth to healthy children. This article on the whole is directed towards people who are on the fence about vegetarianism/veganism and just need an easy way to opt out. Vegetarianism/Veganism is a way of life not just a “diet”, especially if you choose to follow it for compassionate or religious reasons. You fail to understand that if people refuse to follow a healthy and balanced lifestyle, health risks will manifest whether or not they are vegetarian/vegan.

    • Yes, and have you not seen the birth defects that come out of India? They’re some of the worst we see. Indian babies whose mothers don’t get proper nutrition–and that means MEAT–in their diets are being born with horrible neural tube defects.

      You can be “compassionate” all you want, but it’s not going to stop humankind from eating animals. It’s just not going to happen. Vegans are not that powerful and never will be. Instead, you guys are gonna become crippled earlier from Alzheimer’s than the rest of us (because there is a definite link between B12 and brain cells…). It ISN’T just a matter of supplementation; human bodies have a process and they do not normally process supplements as well as they do naturally occurring nutrients, and you’ll still be B12 deficient (as well as carnosine deficient) if you’re vegan. And please do note that once your brain cells have died and formed plaques (the beta-amyloid plaques, and in the case of Parkinson’s, Lewy bodies), you -cannot- get restore them; it’s not as simple as B12 injections (which work for temporary severe B12 deficiency when you’re young). Neurological B12 deficiency symptoms can mimic dementia/psychosis…there really is a reason why we evolved as we did (we ate meat/animal protein!). No matter how noble you think you’re being to the animals, no one can fight the nature of how our bodies work and cannot force us to evolve “not needing meat”. Vegans’ brains are just literally going to plaque up (eventually) worse than meat eaters’, and you’re going to give birth to babies with neural tube defects. That’s just how it is, and you will have to live with that…but hey, if you’re okay becoming senile sooner than the rest of us, fine by us…just don’t make us take care of your idiot asses when it’s too late to help you.

      • I’m a middle class Indian vegetarian myself with access to decent quality food, my whole family, whole community has been vegetarian for thousands of years. In the last 100 years of history that I know about my forefathers, we dont have crippled babies or alzheimer’s patients or plaqued brains in my family. We may not be as strong as meat eaters, but then, I”m not delivering furniture for a living so I dont need a reason to be able to carry heavy weights every day. Most older people that I knew in my community lived 75-95 years, they just had the right mix of vegetables, fruits, grains, milk, pulses, exercise and regimen. This is way of life for many many people in India and they are perfectly fine. The babies with birth defects usually happens in the lower strata of the society where there is a lot of meat consumed but in general the quality of food/life is low not in middle class families that get simple and good food.

  41. While I personally chose to live a vegan lifestyle for ethical reasons, a plant based diet is easier on the environment and I have reduced my cholesterol, am no longer pre-diabetic and about 60 pounds lighter.

    • While being a vegan may have helped you, eating meat helped me. Moving to a paleo diet heavy in meat (and of course also veggies) drastically reduced my IBS symptoms, made my migraines go away, and removed my belly fat. I’ve been a vegetarian before and I was overweight and unhealthy, despite not eating a lot of junk food. Everyones body is different. Veganism is not a cure-all that works for everyone. Also, several of my vegan friends are overweight and I think the over processed “meat alternatives” probably have alot to do with that.

    • I would be curious to know if you made other dietary changes when you eliminated animal products from your diet. For example, did you eliminate or reduce processed foods, sugars, refined grains. (People who “go vegan” for health reasons would typically do these types of things.) Also, did you reduce the number of calories you ate?

  42. Hi,

    I’ve been a supporter of Paleo lifestyle for a number of years. I can’t deny the health benefits. Unfortunately I’ve had to cut down on my meat consumption recently because of startling statistics concerning the amount of meat produced for the planet as a whole.

    In 2012 70 billion animals were reared for food consumption* And a study by the National Academy of Sciences showed that livestock production is one of the most destructive forces driving climate change^

    Raising animals to eat produces more greenhouse gasses (via methane and nitrous oxide) than all of the carbon dioxide excreted by automobiles, boats, planes and trains in the world combined.

    Industrialised livestock also contributes to deforestation used to rear animals or grow soya to feed them.

    We could turn to the seas and oceans. Sadly 53% of the world’s fisheries are fully exploited, and 32% are overexploited, depleted, or recovering from depletion** and Unless the current situation improves, stocks of all species currently fished for food are predicted to collapse by 2048^^

    I’d like to know what you think the future holds for the Paleo diet within the context of climate change.




    • In regards to the environmental impacts of eating meat, the solution is to garden and grow your own meat (chickens, or larger animals if you have more space), or buy from people who are using sustainable practices. Look up the Savory Institute (named for Allen Savory, not the flavor of meat!) and see how cattle can be used to improve the landscape and enrich the soil. Or watch videos of Geoff Lawton or Sepp Holzer and see how animals are incorporated in a permaculture design. Yes, the current commercial methods of meat production are terrible for the environment, but it does not have to be that way.

      • Agree completely. Raising your own meat is ideal. It ensures a humane, healthy life for the animals and healthy, leaner meats on the table for our families. Unfortunately, many families do not have the potential to do this. The alternative is buying local grass-fed beef, pork by pigs raised on pasture and free range poultry. It is more expensive, but healthier and ensures humane treatment of the animals – please no comments about it being inhumane to humanely kill livestock.

        The one area Andy is so off base is that he fails to recognize the environmental consequences of a vegan diet. Farming is a significantly industrialized industry with lots of machinery. An argument can be made that farms contribute to climate issues just as much because of deforestation and draining of wetlands, as well and because the large amount of nitrous oxide emissions from huge amounts of pesticides – most vegans are not organic vegans. Agriculture also consumes the most oil when you consider machinery and transportation.

        It is also hard to make an argument for a vegan diet being healthier. Vegans replace meat and meat by-products with GMO foods and processed foods like wheat, flour and sugar. Most of the studies you see are vegans compared to the average non-vegan. There is no doubt that the majority of Americans are not healthy eaters, with most consuming a lot of fast food, chips, sodas, etc.

        At the same time, a high percentage of vegans are health conscious – even if misguided. A health conscious person will eat better than one who is not. A survey that compares a health conscious vegan to a health conscious omnivore would seem to provide a better comparison.

        A whole foods diet will trump a vegan diet health-wise anyday. A vegan diet will still trump a high carb, fast food diet.

        • Mike you seem to forget that most land and machinery is being used for farming plant based foods to feed the millions of cattle, pigs and poultry. Please educate yourself before commenting or you will forever be a denialist.

  43. My close relative is a vegan. Takes Vitamin B12 supplement regularly.Recent extensive blood tests prove
    all parameters perfectly right.

    I rest my case here.

  44. Pingback: Vegetarian and Vegan Diets: Nutritional Disasters Part 3 : The Paleo Diet™

  45. i take the new “RAW” protein supplement from whole foods and rainbow vitamins for men with joint supplements for vegans, no soy in my vegetarian lacto/ovo diet. i play drums at least 1 hour a day, and i’ve had no health issues “ever”. i’m 55 5’7″ weigh 145 with a body fat ratio of 11% and no wrinkles and all my hair as of yet! people can’t and won’t believe my age unless i whip ut my drivers license and i have achieve orgasm at least once a day and up to 6x of sex on our vacation weekends all of my adult life! my eyes are slowing thats it. go veggie but take a protein supplement and no soy if you;re a guy of avoid the female estrogen, good luck!

  46. Pingback: Vegetarian and Vegan Diets: Nutritional Disasters Part 2 : The Paleo Diet™

    • Yes, because giving a damn about the suffering of other sentient creatures is nonsense.

      As for the health benefits, it’s funny how Cordain himself is one very unhealthy looking and sounding individual. Of course just because he preaches the benefits of the paleo diet doesn’t mean to say he follows it himself, but if he does then I’m sorry, I’ll stick with the dietary plan of the kind and the decent over the morally bankrupt. It doesn’t seem to have harmed people like Iyengar, Krishnamacharya, etc, who all lived into their nineties or beyond.

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