Blood Type Diets

My wife recently purchased some vitamins at a General Nutrition Centers (GNC) store. While there, she overheard one of the employees explaining to a customer that she needed to adjust her diet based upon her blood type. Have you ever experienced such nonsense while shopping there?

According to the Toronto Vegetarian Association:

The “blood type diet” theory has gained widespread attention from the public since the release of “Eat Right For  Your Type” by Peter J. D’Adamo, N. D. (G. P. Putnam’s Sons, New York, 1996). The book's basic premise - that Type O's are the dominant, hunter-caveman type that require meat in the diet, that Type A's are docile vegetarians, while Type B's are dairy-eating omnivores - has become a manifesto for many people to rationalize including regular portions of meat and other animal products in their diet.  ("After all, my ancestors did it.")  However, the "blood type diet" theory, and the book that promotes it, presents many problems that prevent me from seriously basing any of my dietary choices upon them.

One of the book's most disturbing characteristics is 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. Then, on Page 53, D'Adamo states that, "...certain beans and legumes, especially lentils and kidney beans, contain lectins that deposit in your muscle tissues, making them more alkaline and less charged for physical activity."  This is quite a serious scientific charge, and an alarming thought if you are blood Type O - namely, that after eating a bowl of bean chili or lentil stew, lectin proteins are depositing in your muscles and altering their function, changing their acidity, and diminishing your capability for physical action.

Since most people are unaware of their blood types, let alone what foods are "evolutionarily inappropriate" for them to eat, it is reasonable to assume that on most days most people eat the "wrong foods" for their blood type (e.g., Type O eating wheat, Type A eating meat, etc.). Thus, according to D'Adamo's theory, most everyone experiences repeated showers of agglutinated red cells throughout their bloodstream after most every meal – day after day, month after month, year after year. If the capillary beds in your heart, lungs, kidneys, brain, eyes, and other essential organs are subjected to barrage after barrage of agglutinated red cells, they will eventually begin to clog up. These micro-areas of diminished blood flow would at first cause scattered, then more concentrated areas of tissue damage - with eventually many micro-infarctions scattered throughout these vital structures. The brain, heart, lungs, kidneys and adrenals would soon be irreparably damaged by these processes, resulting in potentially fatal outcomes in millions of people.

[W]hen I read a "one size fits all" statement like on page 63, "Type O's do not tolerate whole wheat products at all," I have to ask, "What does he mean, 'at all'?" Do Type O's eat a whole wheat cracker and fall on the ground holding their abdomen and vomiting - or worse yet, suffer immediate brain damage due to their blood cells agglutinating throughout their brain? How much wheat can a Type O eat before their blood agglutinates?  One hamburger bun? One noodle?

Another assertion in this book that make me not want to recommend it to my patients is on page 53, where D’Adamo writes that: "This condition, called hypothyroidism, occurs because Type O's tend not to produce enough iodine." The reality is that the body does not "produce" iodine at all, any more than it produces calcium, magnesium, sodium, or any other earth mineral. Iodine is a halogen element, related to chlorine and bromine, which is taken up by plants from the soil and in the sea – which are then consumed in the diet.

Remember, there is nothing sacrosanct about the ABO blood typing system devised by Dr. Landsteiner in the 1920's. It is only one system classifying more than thirty proteins on the surface of cells that determine other blood groups, with names like Auberger, Diego, Duffy, I, Kell, Kidd, Lewis, Lutheran, MNSs, P, Rh, Sutter, and Xg. This means that food selections that may be "right" for the ABO blood group system might be "dead wrong" for someone's Kell or Kidd antigens. Why are we deifying the D-galactosamine-fucose molecules on the red cell surfaces that determine ABO Type?

According to Diet Bites:

At times, the above referenced book is frightening - filled with mumbo-jumbo 'facts' that will leave Type A's frightened to drink milk, and Type O's running from the wheat fields even though there's not a scarecrow in sight! It is my belief that this dream weaver has spun a best-selling, illustrious evolutionary fairy tale from Never-Never Wheat Land.

Brian Johnson comments:

Of course, the theories presented in the book have been met with criticism from many within the medical community—citing the lack of scientific data. One critic--Dr. Victor Herbert (who studies blood and nutrition at New York's Mt. Sinai Medical Center) so generously commented that “linking blood type and diet is pure horse manure.” Eww.

He continues, blood type has "nothing to do with...how we handle the food we eat.” D’Adamo’s response: "All ideas that are revolutionary are going to engender opposition...because they are very threatening."

His advice: “Determine your blood type and follow your blood type diet for 2 weeks. Experience the results and decide its value for yourself.”

My perspective: The only scientific element that everyone acknowledges is the fact that individuals with Type O blood have a greater incidence rate of stomach ulcers than other blood types and individuals with Type A blood have a greater incidence rate of stomach cancer thank other types. That information is published in scientific journals. D’Adamo’s lab experiments are not; they have not been subjected to rigorous peer review and, therefore, they are often criticized by those in the more conservative medical community. Further, his application of physical anthropological theories of evolution are obviously not scientifically “proven.” They are theories.

At Cellular Nutrition we can read:

Since the "eat-right-4-your-type" concept mainly focuses on dietary lifestyles being matched to blood groups, it would stand to reason that blood types should match the chemical and nutritional profiles of an individual - sort of like the Metabolic Typing of patients - where diets are adjusted according to someone's biochemical or genetic make-up.

Unfortunately, there is no practical or clinical match whatsoever - just like eye color and hair color are not a practical or clinical indication of a person's present or future medical risks (other than those with blue eyes or red hair being more prone for sun damage).  Years ago, plotting the Biorhythm of an individual was another popular concept that had its followers track someone's physical, intellectual and emotional well-being (to identify critical days), although this method equally lacked scientific support.

Of course some people I have talked to mentioned that ever since following the "eat-right-4-your-type'' recommendations, they had lost some weight or otherwise felt better - which just proves that there are always some people that benefit, no matter what system is marketed.  However, when asked about any specific changes made, they invariably consisted of lifestyle changes that are universally considered to be beneficial, regardless of someone's blood type (improving one's diet and cutting out junk foods).

The notion that individuals with certain blood types suffer from specific medical problems (i.e. "Type O is commonly affected with hypothyroidism, high stomach acid [leading to ulcers], and thinner blood...") is incorrect -- there is a major difference between a "risk factor" or "reduced resistance" and actually suffering from a disorder. Many conditions change over a lifetime, but would have to remain fixed according to the premises of the "Blood Type Diet."

Fluctuating nutritional requirements as a result of aging also invalidate "eat-right-4-your-blood type" concepts where a blood group-specific lifestyle is supposed to be maintained throughout a lifetime. For instance, a lot of changes take place post middle age.  Along with the usual hormonal slowdown, an individual's stomach acid, potassium, or zinc levels frequently decline, while phosphorus and/or sodium levels / retention tend to increase - independent of dietary intake or blood type.

Given all of these problems, why would someone at GNC be recommending it? Do the people at GNC get no training in nutrition? If not, why should they be permitted to recommend specific diets — lacking medical or nutritional certification of any sort, aren't they stepping outside the boundaries of what is justified?

My wife buys vitamins there because the prices are good. I'd rather find someplace better, now.

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