A Closer Look at the Blood Type Diet

Just Eat an Apple
Fall 2002

A Closer Look at the Blood Type Diet
Compiled by Frédéric Patenaude

"Blood is magical. Blood is mystical. Blood is alchemical."
 —Dr. Peter J. D'Adamo, author of Eat Right For Your Type

The Blood Type Diet, a new diet fad started by Peter J. D'Adamo with the book Eat Right For Your Type, has received a lot of attention in the last few years. According to D'Adamo's theory, we should be eating according to our blood type, not according to proven health principles. In his book, he pictures Type A's as docile vegetarians. Type B's as dairy-eating omnivores, and Type O's as the dominant, hunter-cavemen meat-eaters. This new book has become a manifesto for many people; it is a way to rationalize the regular inclusion of meat and other animal products in their diet. In this article I will demonstrate why the blood type diet cannot be taken seriously, how it works, and how it can actually hurt people.

"According to D'Adamo, our ancestors were all type O blood and meat-eaters. Later, as they learned to cultivate crops the blood type A appeared. Then between 10,000 years ago and 1000 A.D., types B and AB bloods started to evolve. The latter apparently have the most tolerant and evolved digestive systems. D'Adamo is a naturopath and developed his theory during his studies. Later came the dietary suggestions that our foods should match our blood groups based on ancestral eating habits.

"The blood type diet is not based on any solid science. The diet he recommends for type O, the most common group, is very similar to the Atkins diet, which is a diet high in protein and saturated fats. All the research in the past 20 yeas has shown that diets high in saturated fats coming from animal sources lead to cardiovascular disease and some types of cancer.

"But it's D'Adamo's theory of blood group evolution that is complete hogwash. The molecular evidence for the different ABO groups shows that these blood groups developed maybe earlier than 5 million years ago. An array of blood groups is not any way unique to humans. Gorillas and chimpanzees possess similar. So, by the time you arrive at Homo Sapiens—US!—there is not a scrap of evidence for the existence of one blood group that evolved later into several, and the new DNA signature testing demonstrates this adequately. Dr. D'Adamo is wildly out of date.

"The migration of people out of Africa happened long before the development of agriculture, and the migrants took their diverse blood groups with them, so there is no evidence that any one belonged to a specifically hunter type." (Declan Twohig of the Rea Centre)

Let's see what Dr. Klaper, a medical doctor and an expert on the vegan diet, has to say about the book Eat Right For Your Blood Type:

"One of the book's most disturbing characteristics are the frightening images that the author calls forth without providing scientific documentation. For example, D'Adamo hangs much of his theory on the action of lectins, proteins found on the surface of certain foods that can cause various molecules and some types of cells to stick together. He blames lectins for serious disruptions throughout the body, from agglutination of the blood cells to cirrhosis and kidney failure (page 24). He even scares the reader about these lectin "boogie men" with the tale of ex-KGB agent Georgie Markov who was murdered with an injection of the ultra-potent lectin, ricin…

"If one is going to make a statement like that—and publish it in a book destined for the New York Times best-seller list and intended to change the eating habits of a nation—I believe the author is obligated to present solid scientific evidence of supporting their assertions which D'Adamo repeatedly fails to do. (An example of an author who presents credible proof is Dean Ornish, M.D., who published in his book the "before and after" photographs of X-rays demonstrating increased blood flow through arteries which had opened more widely after patients had participated in his diet and lifestyle program)" D'Adamo presents neither photos nor corroborating studies to support his speculations.

Meat-Eating Eugenics?

Klaper: "Also disturbing is D'Adamo's portrayal of people of vegetarian persuasion. Where in the book, he tells flesh-eating Type O's that they have a "genetic memory of strength, endurance, self-reliance, daring, intuition, and innate optimism.

"…the epitome of focus, drive… "hardy and strong, fueled by a high protein diet" (is he describing a Type O "master race"?), he paints the "more vegetarian" Type A as submissive tofu eaters, "biologically predisposed to heart disease, cancer and diabetes" (pg. 97).

He paints Type A's with personalities "…poorly suited for the intense, high-pressured leadership positions at which Type O's excel" (p. 142), stating that, in pressure situations, people with Type A blood "tend to unravel" and "become anxious and paranoid, taking everything personally." Finally, on page 143, he saddles the group with the dark image of Adolph Hitler, "…a mutated Type A personality." D'Adamo's system seems to create a "blood type astrology" ("What's your type? O Positive? I knew it! So am I!") that imposes strange, limiting stereotypes on very complex human beings."

Blood Analysis

Klaper: "Is the blood type the ultimate determinant of successful adaptation to a particular dietary style? How do we explain the experience of people who say, "I tried to be vegetarian and it didn't work for me so I added some meat back into my diet and I feel better. I guess I'm a Type O caveman," or "A practitioner of 'live cell' analysis stuck my finger and I saw my blood agglutinate! He said I must have eaten foods wrong for my blood type!" I hear variations of these two statements several times per year. Does either of these phenomena validate D'Adamo's blood type theory?

"First, the red cell clumping on the TV screen… I have walked through many medical meetings and health expos and seen this demonstration set up and performed many times. A subject's finger is punctured and a drop of their blood is placed under the microscope slide with the image projected on a large screen or television monitor. The results can appear quite dramatic as a person often sees on the TV screen their red blood cells, platelets, and other cellular elements apparently misshapen and clumped together. It can then be an opportune time to convince the startled person that their blood is laden with toxins or deficient in vital minerals or some other nutrient – and then sell them the 'necessary' supplements that the 'live cell analyst' happens to be purveying.

"Though the images may be graphically convincing, the unsuspecting subject is probably unaware that they may have just witnessed a biological parlor trick. The 'live cell analyst' has probably failed to inform them that the 'agglutinating' effect seen on the screen can be produced by a number of factors, most having nothing to do with lectins, blood type or any other forces beyond the physics and chemistry of a drop of blood on a slide. Remember, that a drop of blood on the microscope slide is very different than a drop of blood flowing through your bloodstream."**

Why Doesn't the Vegetarian Diet Work Sometimes?

Klaper: "After months or years on a flesh-free diet, these individuals might experience deterioration of their health or energy, only to feel better upon resumption of meat ingestion. To the person, this may seem like confirmation that they are 'natural meat eaters.' rather, it may be evidence of an acquired dependency on flesh-borne nutrients formed through early eating patterns. If this is the case, it may be possible to prevent, repair, or at least compensate for these imbalances through provision of additional nutrients, removal of inhibiting substances in the diet, varying combinations of food, etc., utilizing foods of plant-based origin. There is much to learn about the subject and much research needs to be done.

"In my experience, these problems are not encountered in people raised on vegetarian diets from infancy. This effect might be especially pronounced in long-term omnivores who make an abrupt change to a vegan diet, as opposed to those who taper flesh foods out of their diet more gradually It may be that some "omnivore-from-birth" people who desire to sustain themselves on a vegan diet may have to make a more graded transition to completely plant based foods, sometimes over several weeks or months, to give the body time to 'gear up' its metabolic machinery. In other words, what appears to be a 'natural need for meat' may really be the need for an attenuated weaning process from animal products in order to overcome metabolic patterns begun early in life, created largely by cultural practices.

"An additional thought: Less than optimal functlon on a plant-based diet (or any diet) may not stem from a 'lack of meat' or a nutrient deficiency at all, but rather from an individual's other health conditions, like digestive dysfunction, malabsorption by the intestine, parasite problems, adverse immune reactions etc. To me, these are far more likely mechanisms that could explain the 'failure-to-thrive' syndrome occasionally seen in vegetarian and vegans, rather than a genetic mandate to consume flesh determined by their blood type. Much more research is needed to obtain the answers to so many questions in this essential but subtle science."

How the Blood Type Diet Works

Let's analyze the two main solutions proposed by the Blood Type Diet:

a vegetarian diet, without dairy products
a non-vegetarian diet, mostly without grains and without dairy products
The first diet has the benefit of eliminating meat and dairy products. Since eating too much dairy and meat clogs most people up, it is easy to understand why they feel better on this improved diet.

The second diet, the meat diet, mostly avoids grains and completely avoids dairy products. The best thing in this diet, in addition to the avoidance of dairy products, is the near exclusion of all grains and grain products, like bread. It is easy to understand how long-term vegetarians who have been consuming a lot of bread and grains, can feel better when they begin eating some meat while simultaneously cutting down, or even omitting any grain consumption. But these results do not come from inclusion of meat, but by the exclusion of grains and dairy products.

In our opinion, the natural diet of humans is composed chiefly of fruits and vegetables, with the addition of some nuts and seeds. This means no bread, no grains, no fish, and no dairy products. Both of the main Blood Type Diets in D'Adamo's book partly achieve this goal, and that is why people feel better on these diets than they do on some vegetarian diets that rely heavily on grains and dairy.

Because I am a blood type A, some people could say, "But yes, that's why you feel good on your vegetarian diet!" I would then say that I have met dozens of long-term (some for over twenty years) strict vegetarians, who eat no meat, no fish, no animal protein whatsoever, but who are blood type O.

Recommending Poisonous Foods as "Highly Beneficial"

D'Adamo divides foods into three categories: those that are highly beneficial, neutral, and ones to avoid. A highly beneficial food acts like a medicine, whereas a neutral food acts like a food. Foods to avoid are those that act like a poison within our bodies.

Since I am a blood type A, I have taken a look at D'Adamo's recommendations for my kind. Apparently, coffee would be highly beneficial, as well as red wine. But I should definitely avoid beer and sodas. I personally know that coffee is not only a poison to everyone, but to me in particular. I personally can't stand garlic, but according to D'Adamo, it would be highly beneficial for me to eat some. Fresh figs, apricots, and pineapple, but I am to avoid oranges, mangoes, and tangerines. If I understand correctly, they are poisons for me. Now in what alternate universe would I be living in if coffee became my medicine, and oranges my poison?

That is too bad for blood type O's, who like myself are not allowed to have oranges. But what makes me really jealous is that they can have mangoes while I can't. In the meantime, we'll pig out on fresh figs, which are beneficial to both of us. But while blood type O's cannot have coffee, they can drink beer in moderation.

It is obvious that all these ridiculous recommendations are not based on anything scientific. D'Adamo never explains why one blood type should eat or avoid certain types of fruit.

It appears that we can only infer one thing from the evidence presented in this book—he made everything up.

The Emperor's New Clothes

I would like to conclude this article with a text by John J. McMahon, Jr., N.D.

"The Blood Type diet has become a nutritional emperor's new clothes in my profession and in pop nutrition. Criticism of it is ignored. Naturopathic physicians and people offering nutritional advice need to evaluate any protocol they embrace."

The Archaeology of Diet

"The theory of diet according to blood group implies that blood types have evolved or mutated over the course of human existence on this planet. This is not the case. We share the ABO blood groups with chimpanzees and gorillas, indicating that these blood groups have been a part of our biological heritage for the past 5 million years (Christopher Stringer Ph.D. Africa Exodus, 1998). Australopithecine, our earliest hominid ancestor, is universally considered vegetarian by paleoanthroplogists. Professor Lewis Binford, considered the 'Father of New Archaeology,' makes a good argument, using modern archaeological techniques, for a predominantly vegetarian diet throughout human speciation even during the Paleolithic era.

"D'Adamo's main references are two arcane books of anthropology by Mourant titled Blood Groups and Disease and Blood Relations: Blood Groups & Anthroplogy. These books are the source for the blood type-anthropology timeline on page 6 of the blood type book. I have read Mourant's work; it is available to anyone via interlibrary loan from the UMass library.

Mourant's books are, without question, the worst books of anthropology I have ever read and I've had to read some very bad anthropology. I majored in anthropology as an undergraduate at the University of Notre Dame. Mourant engages in conjecture that Eat Right For Your Type presents as fact. For instance, there is no basis in archaeology for the claim that blood type O is consistent with an early hominid, warrior, and flesh-eating stage of human evolution. Cro-Magnon, the ancestor who is described by Eat Right For Your Type in this fashion, actually was creative, compassionate and, given the elaborate burials found at Cro-Magnon digs—a very spiritual being. Cro-Magnon also appears to have gotten at least 70% of his/her calories from wild vegetation (Stringer, African Exodus, 1998)."

Naturopathy, Medicine, & Diet

"The physicians who defined the practice of naturopathy, Dr. Henry Lindlahr & Benedict Lust, recommended and ate a vegetarian diet. Recent research using vegetarian diet by Ornish (successful treatment of heart disease), Lindahl (successful treatment of asthma), Kjeldsen-Kragh (successful treatment of rheumatoid arthritis), Barsotti (successful treatment of kidney failure patients on dialysis), Chen, Campbell & Peto et al (lowered cancer rate) as well as Wahlqvist and Aldercreutz (successful care for menopausal symptoms including bone loss and hot flashes) have validated the reliable, health-promoting impact of vegetarian food choices on human beings. People of blood group O and B, for whom Eat Right For Your Type recommends daily consumption of animal protein, comprise at least 53% and potentially upwards of 60% of a random sample of the population (Eloise R. Giblett, M.D. Blood Groups and Blood Transfusion in Harrison's Principles of Internal Medicine, 10th Edition, pp 1909-13). Given Eat Right For Your Type's claims, each of the afore-mentioned studies using vegetarian or vegan diet should show a failure rate close to the 55-60% incidence of men and women of blood type O and B in a random research sample. This does not occur.

"The blood type solution ignores this research on vegetarian diet and the common sense conclusion about percent blood group variables, prescribing regular consumption of beef to people of blood type O and B. Regular consumption of beef is consistently associated with increased incidence of colon cancer (World Rev Nutr Diet 66:3446-61, 1991)."


"The blood type solution discourages anything more taxing than low-impact aerobics in people of blood type A in spite of the unequivocal evidence that more rigorous exercise is vital for prevention of osteoporosis (Spine, 1996; 21:2809-13).

"The 'blood type solution' encourages sundry capricious restrictions on diet, exercise and life. Good science and common sense makes this theory impossible for me to take seriously."


My Critique of Fad a Diet The Blood Type Solution, John J. McMahon, J., N.D.
A Review of Peter D'Adamo's Eat Right 4 Your Type, by Declan Twohig (The Rea Centre)
Challenges to the Blood Type Diet, by Michael Klaper, M.D.


**Contrary to Klaper's opinion, (which I respect on most issues) live blood analysis in competent hands, is an excellent tool to discover the condition of your blood. _Rhio.

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