Saturday, May 29, 2010

A Critical Examination Of Blood Type Diets

This is one of the most popular questions I get when I discuss nutrition and health. What do I think about "blood type diets". My answer is that it sounded interesting but I don't know if the science behind it is sound. 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 hot got his blood types wrong according to evolutionary science. Dr. Loren Cordain PhD explains it all as he examines this popular diet theory...

Enjoy the explanation.....

Dr. T

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.


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

Dr. Narson is a 2-term past president of the Florida Chiropractic Association’s Council on Sports Injuries, Physical Fitness & Rehabilitation and was honored as the recipient of the coveted Chiropractic Sports Physician of the Year Award in 1999-2000. He practices in Miami Beach, Florida at the Miami Beach Family & Sports Chiropractic Center; A Facility for Natural Sports Medicine.


V. lagra said...

Of course blood type diet sounds interesting but I also agree there is no science according to that.

TJ said...

You use only 7 references (2 from the D'Adamos) to disprove a book supported by over 120 scholarly articles and countless hours of the author's own research? Way to be thorough. Who's paying you to endorse their diet?

Dr. Todd Narson said...

"Drive55" it's not the quantity of the research or scholarly articles, it's their accuracy. There are inaccuracies throughout with his references for simply the time line for how humans evolved, where they evolved from, etc.. Loren Cordain, PhD has over 300 articles published in human evolution & diet and is an authority on the subject. I think Dr. Cordain's article does quite enough to refute the facts of the blood type diet. As he pointed out, it will work for a certain percent of the population, but because of the holes in his science, it doesn't work for most or all.

And to answer your question about "who pays me"??? My patients pay me to help them get results.

I have to admit though, in theory The Blood Type diet did sounds nice.

'nuff said

Unknown said...

Yes, D'adamo got it wrong on the dates and evolution. But what you fail to mention is that he actually examined the different blood groups under the microscope and TESTED what foods/lectins caused the blood of the different types to agglutinate. And THAT builds the premise for his food recommendations. Either Cordain didnt fully read his book or he conveniently skipped that part.

V said...

I would first like to state that I am not a scientist, but I do not believe that one's diet ought to be influenced by one's blood type. Nevertheless, I would like to pose a question...

You state that, "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 ago."

However, I note that Native Americans are overwhelmingly type O+ with some distribution of A+ in the more northern tribes. (see:

It appears from this distribution map that Central and South American Indians are completely devoid of A or B, with O types approaching 100% of the population.

I 'assume' that the distribution of A types arrived later than those of O, in successive waves of migration.

Therefore I must ask if O is indeed more ancient than A, since these Native Americans are now thought to have arrived into the Americas at a much earlier date than the previously accepted 11,000 years or so. I have heard estimates of possibly upwards of 30,000 - 40,000 years ago.


V said...

Hello again:

Possibly I will, in part, be answering my own question, but I have continued my reading on this subject since posing it earlier...

Apparently there is a correlation between blood type and one's susceptibility to malaria. Researchers have found that malaria presents less severely, or there are fewer severe cases of this disease, in those of blood type O+.


If, as is supposed in Dr. Cordain's refutation of the "Eat Right For Your Blood Type" diet, blood type A is in fact the more ancient type, then it appears that proto-humans with type O+ may have had greater survivability in the face of malaria. I'm willing to hazard a guess that this mutation would have given them the edge needed to multiply their numbers and perhaps become the creature we recognize as fully human today. Perhaps it would be more accurate to say that O+ is the most ancient blood type of homo sapiens, but not of much earlier human-like beings. After all, we branched off from the ancestors of chimps and gorillas a very long time ago.

Again, all thoughts are welcome. Thanks!

Aspiring Steph said...

I agree with "V" above,
I am aware that blood type diet lacks scientific evidence, but it is definitely interesting.
I'm an A, and the foods recommended or not-recommended does really work better for me.
But most of all, chimpanzees and other apes are "A" and they happen to be basically "vegans". When "homos" started eating meat, I've read before that's when the "mutation" occurred for us to be more type O's and we were able to take a huge evolutionary step.
Well, I am not criticizing or anything, but I am just really curious. Doesn't this suggest that perhaps "some" parts of the BTD makes sense?


Dr. Todd Narson said...

Interestingly, I'm sure we all remember from high school and learning how chimps, apes use a stick as a tool to get termites & ants out of their respective mounds. This is one instance that shows apes and chimps aren't vegans.

The eat for your blood type is interesting as it seems that your lineage should influence what fuels your physiology. I always tell people if they want to be healthy, research their ancestry and eat like they did. But there ends up being some commonalities when you go back far enough.

Based on the credibility of the research, I'd have to go with Loren Cordain on this. With his history of research and the too numerous to mention..times he's been published in this area really goes way beyond that of the blood type diet.

The fact that the blood type diet doesn't work for a large % of the people that try it is quite telling.

When eating with paleo principles, everyone that dose it seems to respond quite favorably.

Love the discussion. You guys really make some outstanding points.

Dr. T

Andy said...

Stephanie, Chimps could not at all be described as vegan. Although they primarily eat fruit, they also eat meat, including other primates, birds and eggs, and insects.

Dr. Todd Narson said...

Based on anthropological research, our genes are linked back to about 4.5 million years ago (the last 200,000 of which are virtually unchanged and the last 40,000 the exact same). During none of this time were humans ever vegan or vegetarian.

For that matter, it's well known in (for those that actually study it rather than listen to hearsay) that chimps are not vegan or vegetarian or Fruitarian, they are omnivore. During the dry season they eat meat, small antelope and as pointed out above, other small monkeys. They've been well known for using sticks as tools to retrieve ants and termites from mounds. So the argument that we are supposed to only eat vegetarian or vegan is absolutely ridiculous.

Jess said...

I've always been a little skeptical of the blood type diet, but that hasn't stopped me from loosely implementing it because I have leaky gut. It's really frustrating trying to find food that works. The guidelines from the blood type diet made it a little easier. Many of the foods on the avoid list had a negative effect on me. Lentils and red beans really bothered me where other beans didn't noticeably bother me. Your points make a lot of sense; but what about lectins? You don't address the discussion of lectins in D'Adamo's book which made a lot of sense to me. Thank you.

Anonymous said...

I appreciate this critique of the blood type diet, it feels very fair and balanced, and based on science. Such a refreshing approach.

I think it is easy for us to look for nutritional information in absolute terms. My issue with this diet is the idea that there are foods that are "all good" or "all bad" for you. Even if our ancestors ate certain foods, and maybe those are the easiest for us to process, humans of all blood types have been evolving over hundreds of years and I have a hard time believing that nutrition has to be a rigid formula in order to be considered natural or healthy. When you see healthy 100 year olds being interviewed, usually they describe their eating habits in a very simple way. I haven't heard any 100 year old say that they got to that age in good health because of something like the blood type diet.

Dr. Todd Narson said...

I think your comments are very appropriate and bring up a great point. The "caveman" diet wasn't written in stone because of their general nomadic life-style. They roamed with their food sources. Veggies and fruit would grow in different regions at different times of the year, animals would migrate with their primary food sources and the caveman would do the same. As caveman broke off into various regions, several variations of the "paleo diet" would emerge as different foods were available in different regions of a continent. So there is some variation.

However grains were a starvation food only consumed in times of desperation. It's not something that 99.8% of Paleolithic people are for out entire genetic time on earth. Combine this with the fact that grains have substances to prevent absorption in the digestive tract (so they can make it through an animals digestive tract, be pooped out and then sprout to grow the next generation of plant species, makes them a food we shouldn't consume today.

But yes, the diet of a caveman did vary with the season and locations. But overall, is MUCH MUCH different that what we see in most societies today...