A Critical Examination Of Blood Type Diets

This is a pretty popular questions I get asked. “What do I think about ‘blood type diets?'” My answer is always it sounds good but I am not very convinced…there just isn’t much scientific evidence to support it.  Turns out, I was right. Blood type diets work for 44-62% of the people but for all the wrong reasons. When he ends up recommending to 44-62% of his readers is a paleo-diet. Unfortunately, his reasoning is all wrong because he got his blood types wrong according to evolutionary science. Dr. Loren Cordain PhD explains it all as he examines this popular diet theory…

A Critical Examination Of Blood Type Diets

– by Loren Cordain, Ph.D., Professor

The History And Characterization Of Blood Type Diets

Blood type diets were first popularized by Peter D’Adamo, a naturopathic physician, in his best selling 1996 book, Eat Right 4 Your Type1. The inspiration for Dr. D’Adamo’s book came from subjective clinical impressions of his father, James D’Adamo; also a naturopathic physician who first proposed this concept in his book, One Man’s Food is Someone Else’s Poison 16 years earlier in 19802. As a member of Bastyr College’s first graduating class of naturopathic physicians in 1982, Peter became interested in attempting to validate his father’s subjective and personal observations from reviews of the scientific and medical literature – thus the fundamental reason for Peter writing his hugely successful diet book.

The underlying premise for Peter’s dietary ideas is that ABO blood type is the most important issue in determining healthful diets. He advocates separate diets for people with one of the four most common blood types (A, B, O or AB), and has further subdivided his dietary recommendations into three arbitrary ancestral categories: “African, Caucasian and Asian.” Hence 12 subgroups (4 blood types x 3 ancestral categories) exist – each with differing dietary recommendations. Each blood type diet includes 16 food groups which are divided into three categories: 1) highly beneficial, 2) neutral and 3) avoid. For each of the 12 subgroups differing recommendations exist for the three food categories. If these nutritional recommendations sound somewhat complex to you, I had to re-read them about a dozen times to get the drift myself. Although I don’t want to get ahead of the game, for the observant reader, you may be curious to know how Dr. D’Adamo dreamed up this complex dietary system and if a long trail of experimental human clinical trials exist to support Peter’s recommendations? I, too, had to ask myself these same questions.

Before we get into the science or lack thereof of the blood type diet, I’ve got to flesh out a few more of the underlying concepts. Dr. D’Adamo believes that blood group O (“O for Old”) was the earliest human blood type and that all humans at one time maintained this blood group before the subsequent evolutionary appearance of blood types A, B and AB (reference 1, pp. 6-13). Accordingly, Peter believes that people with the O blood type had ancestors who were skillful hunters and whose diets were high in meat and animal proteins. For modern people with the O blood type he advocates a high meat, low carbohydrate “hunter” diet, with virtually no wheat, few grains or legumes and limited dairy products. Do these dietary recommendations ring a bell for you, or sound vaguely familiar? Keep this thought in mind, as it may well explain the lasting popularity of Peter’s first book.

Peter now goes on to explain to us that blood group A (“A is for Agrarian”) “appeared somewhere in Asia or the Middle East between 25,000 and 15,000 B.C.” . . . and “allowed them to better tolerate and absorb cultivated grains and other agricultural products” (reference 1, p. 8). For type A’s, Dr. D’Adamo recommends a mainly vegetarian diet – the diet that he personally follows. However, more importantly he recommends that blood type A’s also avoid wheat and dairy (do these recommendations also sound familiar?) and replace meats with some “highly beneficial” fish and seafood – Hmm, lots of fresh fruits and veggies for type A’s, little wheat or dairy and fish instead of meat? Keep these recommendations in mind.

Peter next tells us that blood type B, “developed sometime between 10,000 and 15,000 B.C. in the area of the Himalayan highlands – now part of present-day Pakistan and India (reference 1, p. 10). Peter suggests that type B’s have evolved the most varied diet and can include both meats and dairy in their daily menu, but again should avoid wheat. Before we move on to the final blood type (AB) it should be noted that Dr. D’Adamo generally eschews highly processed foods (chips, pastries, candy, ice cream, snack food, fast food, etc.) for all blood groups – once again, does this not sound like another familiar dietary suggestion?

From Peter’s diagram on page 6 of his book, he indicates that blood type AB appeared first in humans sometime between 500 B.C. and 900 A.D. He characterizes “AB is for Modern” and states “Until ten or twelve centuries ago, there was no Type AB blood.” (reference 1, p. 13). Peter indicates that AB’s are a conglomeration of type A and type B blood types, and consequently their diets should reflect a mixture of the recommendations he makes for these blood groups. AB’s are therefore advised to eat meats, seafood and dairy, and to once again avoid wheat.

The Reality And The Science Of Blood Type Diets

The reality of Dr. D’Adamo’s book, Eat Right 4 Your Type, is that it has overwhelmingly become one of the sustained, best selling diet books of the past two decades, and continues to sell well on Amazon and other retail outlets – 14 years after its initial release in 1996. Unfortunately, as I will shortly demonstrate, Dr. D’Adamo’s explanations for the health-promoting effects of his diet have little or nothing to do with ABO blood groups. His claims about the origins of human blood types and the dietary selective pressures which elicited the four common blood types are completely incorrect and have no basis in the current scientific literature. By critically examining the faulty concepts and evidence underlying this book, it becomes almost comical how Peter’s series of errors, incorrect assumptions and conclusions actually ended up with dietary recommendations that may have therapeutic value for about 60% or more of the world’s population. The paradoxical nature of this book (bad science, pretty good dietary recommendations) helps to explain its lasting commercial success.

Actual Origins of Human Blood Types

Peter’s suggestion that O is the original human blood type is incorrect. Studies in humans, chimpanzees and bonobos (a specific type of chimpanzee) show that alleles (different versions of genes) coding for the A blood type was actually the most ancient version of the ABO blood group, and was shared prior to the evolutionary split between chimpanzees and hominids five to six million years ago3-5. Hence, Peter’s suggestion that blood type A appeared 15,000 to 25,000 years B.C. in response to dietary changes brought about by the new foods (i.e. grains) of the agricultural revolution is not only incorrect, but off base by about five million years. Now, let’s play a little game of logic and apply the correct data to Peter’s reasoning that “the original ancestral human blood type should be eating a high protein meat based diet.” Since type A is the actual ancestral human blood type (rather than O), if we use Peter’s logic then he – himself a type A – should not be following a vegetarian diet, but rather a high protein meat based diet. These kinds of games of logic – although fun to play – more importantly underscore the fundamental and incorrect assumptions upon which Peter’s book is based.

The next blood type that appeared in the human lineage was B – which split from A – about 3.5 million years ago3-5, not the recent 10,000 to 15,000 years B.C. origin that Peter has proposed. The O blood type split from A about 2.5 million years ago3-5 and consequently does not represent the oldest blood type as claimed by Peter. The only fact that Peter correctly deduced about the origin of human blood types was that AB was the youngest, but once again he completely missed the correct date, as it was actually about 260,000 years ago3 – not the mere 1,500 years ago that he has proposed.

So Peter has got all of his blood group origins messed up, his dates wrong, and the evolutionary splits incorrect. Why does this matter and how does it affect his dietary theories? To begin with, even if we were to believe in Peter’s underlying assumptions that diets should be prescribed upon blood types, he would have to completely revamp his original recommendations. Type A’s should be eating a high protein, meat-based diet rather than the vegetarian fare he suggests. But what about type O’s? With the correct evolutionary information, should they now be eating a vegetarian menu? And what about type B’s and type AB’s – what should they now be eating? Most telling of the logical failings of Peter’s blood type diet is the observation that all four of the major blood types had evolved almost 250,000 years before the coming of the Agricultural Revolution 10,000 years ago. Yet Peter would have us convinced that three of the four major blood groups only came into existence slightly before or after the Agricultural Revolution, and as a direct result from dietary selective pressures wrought by Neolithic food introductions.

So, why has Peter’s book become one of the best selling diet books in the past two decades? Because it works – but only for about 44-62% of the people who adopt it. Remember that for blood type O, Peter advocates a high meat, low carbohydrate “hunter” diet; with virtually no wheat, few grains or legumes and limited dairy products. If we look at the frequencies of the four major blood types for the entire world population, blood type O is by far the most frequently occurring version. It is found in 62% of all the world’s people, followed by A (21%), B (16%) and AB (1-3%)6. In the United States, the four blood type frequencies are O (44%), A (42%), B (10%) and AB (4%)7. So you can see that Peter has essentially advocated a diet similar to the Paleo Diet for between 44 and 62% of his readers. Quite simply, Peter’s diet works for about 44 to 62% of the people who adopt it – not because of their blood type, but because it emulates the same diet that natural selection has designed for us all.

References:

1. D’Adamo, P. with Whitney, C. Eat Right 4 your Type: The Individualized Diet Solution to Staying Healthy, Living Longer & Achieving Your Ideal Weight. Putnam’s Sons, New York, 1996.
2. D’Adamo, J. One man’s food–is someone else’s poison. R. Marek Publisher, 1980.
3. Calafell F, Roubinet F, Ramírez-Soriano A, Saitou N, Bertranpetit J, Blancher A. Evolutionary dynamics of the human ABO gene. Hum Genet. 2008 Sep;124(2):123-35.
4. Saitou N, Yamamoto F. Evolution of primate ABO blood group genes and their homologous genes. Mol Biol Evol. 1997 Apr;14(4):399-411.
5. Lalueza-Fox C, Gigli E, de la Rasilla M, Fortea J, Rosas A, Bertranpetit J, Krause J. Genetic characterization of the ABO blood group in Neandertals. BMC Evol Biol. 2008 Dec 24;8:342.
6. Mourant AE, Kopec AC, Domaniewska-Sobczak K. The Distribution of the Human Blood Groups and other Polymorphisms. Oxford University Press, London, 1976, p. 6.
7. Stanford School of Medicine, Blood Center.

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