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
Although 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 planned“28 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 cycle“28 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
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