Dieting: As Simple as AB?          John Mayer

Since taking this nutrition class I have become aware of the astonishing variety of diet concepts and the vast hordes of Americans grasping for any and all theories that might relieve them of unwanted pounds. Apparently we are willing to try anything to lose weight short of exercising and eating less. I’ve come to believe that the United States of America has an eating disorder.

As one who has never given my weight a great deal of thought or attention (though perhaps I should have), I haven’t paid much attention to diet plans and fads. And I may not be as sympathetic as I should be to the problems of those who just can’t say no to upsizing their servings; most of the world’s population would love to have that problem. I don’t believe that two-thirds of Americans have a glandular problem. But, having almost completed this course, I’m beginning to see that Americans have all the forces of government and skillful corporate advertisers arrayed against them, tempting us to indulge our every appetite – “Snickers satisfies until your next meal” – and then condemning us for being unfashionably fleshy.

It seems, too, that for every fast food advertiser there is another merchant offering books and diet supplements to trim away that fast food fat. Most Americans have no way of evaluating the merits of the various diet plans other than by what they read in uncritical news reports, reactions of friends and blurbs on book jackets. Sadly, there is no national agency to share with us the general consensus of real science, though one might think the Surgeon General’s office could serve that function. So Americans accept the diet plans with the best advertising, not the best research. We are even now engaged in a great national experiment, the Atkins Diet, that will show us whether diets rich in fat and high in protein will improve the national physique or, instead, will increase the average intelligence of future generations through Darwinian principles.

I have only recently, however, become aware of a diet that makes the Atkins Diet seem sensible by contrast; it is called the Blood Type Diet, or the AB Diet. According to advocates of the diet and its originator Dr. D’Adamo, foods that are salubrious for one blood type can be harmful, even deadly, to another. It seems that the blood types are an evolutionary response to available foods and pathogens that our ancestors encountered in the great human diaspora thousands of years ago. As Dr. D’Adamo explained, quoted by CNN’s Brian Jenkins in 1997, “[Blood types] control whether we view certain things in our diet as foreign or friendly…” The doctor dismissed the pooh-poohing of mainstream scientists in nutrition and serology as the knee-jerk reactions of an entrenched nutrition science establishment, fearful of change. D'Adamo said in that interview, "All ideas that are revolutionary are going to engender opposition ... because they are very threatening."

The article goes on: “D'Adamo's ideas are based on evidence that the most common blood type, ‘O,’ goes back to the pre-historic age of hunter-gatherers. As a result, the theory goes, people today with type ‘O’ blood do best eating foods rich in fat and protein. Type ‘A’ blood appeared later in farming cultures, making modern-day ‘A’ and ‘A-B’ blood types better off with diets heavy on grains and carbohydrates. Blood type ‘B,’ evolved after ‘O’ and ‘A’ and is a balance of both, says D'Adamo. Under his theory, a person with type ‘B’ blood can't burn the fat in red meat as efficiently as a type ‘O’ can. Likewise, a type ‘B’ person doesn't burn carbohydrates as fast as a type ‘A’ does.” The report concluded with the account of a Michael Kirshbaum who went to Dr. D’Adamo with a liver condition and itching and upon being instructed to stop eating potatoes, wheat products, chicken and oranges (and given five herbal medicines) was healed. Compelling anecdotal evidence, indeed. 

This all sounds so far-fetched that one might be tempted to dismiss it all as a sort of dietary equivalent of astrology; “Virgos should avoid spicy foods and quarrelsome dinner companions, and always chew everything 32 times.” Who could possibly take such pronouncements seriously? Well, a lot of people, it seems. The first book in D’Adamo’s series, Eat Right 4 Your Type was on the New York Times best seller list, and has sold more than 340,000 copies.  Well, after all, the book was written by a doctor.

The diet, in fact, is often referred to as Dr. D’Adamo’s Blood Type Diet, so we are constantly reminded in reading about it that it is the product of the research and study of a doctor. And doctors are smart. A visit to the Blood Type Diet’s webpage ( ) informs us more precisely that Peter D’Adamo is a Doctor of Naturopathy. The word conjures up an image of a bearded man in druidic costume wandering through the forest collecting roots and berries, but that is an unfair and uninformed reaction on my part; perhaps Doctors of Naturopathy undergo training every bit as rigorous as a doctor of medicine. So I consult the website of what is, reportedly, one of the nation’s top schools of naturopathy, Bastyr University. Indeed, it seems that Bastyr does not accept just anyone into their doctoral program; there are stringent prerequisites that must be met. Their website ( ) clearly states:  “In selecting applicants for admission, the Bastyr University naturopathic medicine program seeks those qualities of motivation, intellect and character essential to becoming a physician. Applicants are considered on the basis of academic performance, maturity and demonstrated humanitarian qualities. Work and/or volunteer experience in health care coupled with an awareness of the field of natural medicine is strongly recommended.” If only I’d known beforehand that I could get an advanced medical degree without the superfluous unpleasantness of chemistry.

Wishing to know more about naturopathy I turned to the Skeptic’s Dictionary
( ) where I read the following: “Naturopathy is a system of therapy and treatment which relies exclusively on  natural  remedies, such as sunlight, air, water, supplemented with diet and therapies  such as massage. However,  some naturopaths  have been known to prescribe such unnatural treatments as  colon  hydrotherapy for such diseases as asthma and arthritis. Naturopathy is based on the belief that the body is self-healing. The  body will repair itself and recover from illness spontaneously if it is in  a healthy environment. Naturopaths have many remedies and recommendations  for creating a healthy environment so the body can spontaneously heal  itself. Naturopaths claim to be holistic, which  means they believe that the natural body is joined to a supernatural  soul  and a non-physical mind and the three must be treated as a unit… Naturopathy is  fond of such terms as ‘balance’ and ‘harmony’ and  ‘energy.’ It is often rooted in mysticism and a metaphysical  belief in vitalism (Barrett).” Which sounds a bit like my impression of Christian Science.

To explore the assertions that underlie the blood type diet in a bit more detail, they are as follows:

Type O'S were the Original Blood Type, the first humans, hunter-gatherers. Their modern O descendents should eat according to their inherited fierce hunter-gatherer natures by eating meat  (lots of protein, few carbs, rather like the Atkins diet), cut out wheat and grains, and exercise vigorously.
Type A's came along after agriculture was invented around 25,000 B.C. or so, and were gentle farmers whose descendents should follow a vegetarian diet high in carbs and low in fat. They should engage in gentle exercise such as yoga or golf (like their ancestors, I suppose). Disregarding the question of whether golf should be included under the heading of exercise, it is obvious that Dr. D’Adamo has never worked on a farm if he believes the work is “gentle.” In fact, I have read that hunter-gatherers actually spent about four hours a day in providing for their basic needs, the rest being spent in leisurely pursuits. Anthropological studies of primitive tribesmen also suggest that they are far less successful in bringing home meat than has been assumed, relying much more on foraged and cultivated plant foods. It is likely that ancient farmers, able to raise and slaughter their own meat, consumed much more of it than nomadic hunters did.

Type B's are called the Balanced Blood Type and evolved between 15,000 and 10,000 B.C. They combine the genotypes of A and O. This blood type emerged as  a result of the migration of the races from Africa to other parts of  the world  “and may have mutated due to climactic changes.” B's  get to eat the greatest variety, the traditional “balanced diet.” They’re the only ones that should consume dairy products. They should exercise moderately, maybe by taking a nice walk.
Type AB's are, apparently, a product of modern Type-Mixing of the races, only having shown up on the earth within the last 1000 years, and they should eat a diet combining the foods of A’s and B’s,  which would seem to mean a vegetarian diet with an occasional cold cut or insect thrown in. Their exercise is even less strenuous than that of the Eloi-like A’s, consisting only of calming exercise and relaxation techniques. Plainly the  type O’s can kick all the other types’ butts.

I’m afraid it is beyond the scope of this little paper to address the fallacies of this fad diet point by point; after all, the last book in the series was a whole encyclopedia. And I’ve yet to pass my first microbiology class, though I am hopeful that that is about to change. But even I was able to spot what I might charitably call carelessness in Dr. D’Adamo’s writing.  For example, in The Complete Blood Type Encyclopedia he mentions, “The  effects of ABO blood group on survival against most forms of epidemic illness is so distinct that a modern day map of the ABO blood group distribution in Europe closely parallels the locations of  major epidemics, with higher densities of blood group A and lower frequencies of  blood group O in areas historically known to have had long histories of repeated  pandemics.” Leaving us to wonder exactly which areas had long histories of world-wide epidemics.

I certainly would not recommend anyone seeking a healthy diet turn to “Dr.” D’Amato’s teachings, rating them as a “1” on a ten point scale of reliability. He definitely has a product to sell. He may, as well, have a philosophy to sell; it seems he is following in the footsteps of his father, also a naturopath and the actual originator of the Blood Type Diet theory. There are a number of books and supplements available from the Eat Right 4 Your Type website, and it seems that particular new diet industry is doing a brisk trade. As I mentioned, I don’t have the expertise to challenge all of the “doctor’s” assertions, but nothing in this entire semester’s study of nutrition has hinted at the importance of dietary restrictions based on blood type. Authorities in the field who have troubled to comment on this particular fad have been unimpressed by Dr. D’Amato’s research, or rather the lack of it. He has yet to present a single study or empirical evidence of the agglutination of blood cells in anyone as a result of eating the wrong foods for their blood types. Having read of the dramatic and deadly effect of such agglutination as a result of sepsis in both microbiology and for the previous paper for this class, it would seem such a danger would have become apparent to real nutritionists long before now.  Dr. Michael Klaper (Doctor of Medicine, in this case) says, “Pathologists and other medical scientists would be very familiar with a syndrome of organ failure due to lectin-induced micro-infarctions (cell death). The existence and intricacies of such a widespread disease would be as well-known as is atherosclerosis. Yet, I am aware of no such description in the pathologic literature and no pathologist I know has ever mentioned this as a cause of any disease in humans.”
( )

Finally, another bit of information I came upon as a result of studies in microbiology also makes me dubious about Dr. D’Amato’s conclusions. It seems that humans share their blood types with the great apes. The CDC website says, “The distribution of ABO blood groups found in baboons indicates that approximately one third are group A, one-third group B, and one-third group AB. Universal donor group O, however, is exceedingly rare. In Americans of Western European descent, the relative frequency of blood types is approximately 45% group A, 8% group B, 4% group AB, and 43% group O.” ( ) Surprising if all humans began as Type O, especially as baboons are the only one of the great apes whose diet includes a significant amount of meat. Our closest relative, the chimpanzee has mostly type A with a small percentage of O’s. Gorillas are all type B. We can only hope gorillas avoid overly strenuous brachiation.

©2004 John Mayer