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Genetically Determined Diets
 This article by Dr. Blankenship, a nutritional chemist, originally appeared in The Journal of Health and Healing and is used with their permission.
James W. Blankenship, Ph.D.
The nutrition section of bookstores is loaded with a vast array of books offering instruction on how to eat to have good health, or how to lose weight. The manifested interest on the part of American people is commendable and justified, since the United States is by far the fattest country of the world with 54% of the adult population and 25% of the children being overweight. Thus, the need and interest by Americans for nutrition information is great and this interest is being met by quite an array of diet instruction books. Unfortunately, a large number of the popular best sellers fall into the “fad diet” category.
One of the most preposterous of these diet books is Peter J. D’Adamo’s book, Eat Right for Your Type. D’Adamo, who is a naturopathic physician, has indicated that “your blood type reflects your internal chemistry” and that “change in climate and available food produced new blood types” (p. 3).
Of course, in his book he tries to relate blood type to the evolution of man and whether the specific group of people were of the hunter-gather class or of the agrarian type of lifestyle. The author further indicates that “your blood type is the key to your body’s entire immune system” (p. 17). Obviously, he is short on scientific support for his many statements.
The author then describes a diet for each blood type as follows:
“Type O is ‘the hunter.’ These individuals ‘thrive on intense physical exercise and animal protein’ (p. 52). Type O should use dairy products and eggs sparingly. Also wheat and most grains should be cut out of the diet. “
“Type A flourishes on a vegetarian diet, and Type A individuals are biologically predisposed to heart disease, cancer, and diabetes” (p.97).
“The Type B diet is balanced and wholesome, including a wide variety of foods…the best of the animal and vegetable kingdoms” (p. 145).
The Type AB can utilize a diet that is suitable for both A and B. “You have most of the benefits and intolerances of Types A and B” (jacket flap).
The description of blood type development and the relationship of the nature of the diet to the blood type is naturally regarded by the scientific community as being absurd. Our blood type (ABO system) is genetically determined at the moment of conception. D’Adamo could just as well have developed a diet plan based on the color of the eyes.
This diet, designed to fit your blood type, can potentially be dangerous. For example, the diet for the Type O, which excludes whole grains and includes heavy usage of meat, can lead to certain nutrient deficiencies besides putting a person at risk for developing cardiovascular diseases and cancer because of high animal fat. Likewise, the Type A diet, which is vegetarian, certainly doesn’t predispose a person to heart disease, cancer and diabetes! The representation of science here is seriously flawed.
Another part of D’Adamo’s theory is the role of lectins, which are proteins that have the capacity to bind to red blood cells and to cause them to agglutinate, or clump. This type of experiment can be demonstrated by adding lectins to blood in a test tube. However, this can hardly be equated to what might occur when a food is eaten.. The digestion and absorption processes minimize the contact of intact proteins with the red blood cells of the blood stream.
The Following quotation describes the D’Adamo theory:
“Simply put, when you eat a food containing protein lectins that are incompatible with your blood type antigen, the lectins target an organ or body system (kidneys, liver, brain, stomach, etc.) and begin to agglutinate blood cells in that area” (p. 23). Sounds very serious! Lectins are widely distributed in our food sources. They are proteins which are poorly digested by stomach enzymes. However, after search of the literature, I was unable to find a report indicating the absorption of any lectin.
A sampling of the literature for common foods that contain small amounts of lectins such as tomatoes, beans, , and peas indicates that theses plant lectins are very poorly digested. However, there is no evidence of intact protein absorption into the blood stream and certainly no evidence is reported for dietary lectins being a hazard in producing agglutination (clumping) of red blood cells in the blood vessels.
In summary, D’Adamo’s book has no documented scientific support for his claims for the various complex diet recommendations designed for the four different blood types. As mentioned above, some of the recommendations post some health risks. Certainly, the U.S.D.A. recommendation for increased consumption of fruits, vegetables, and grain products applies to all blood types with expected health benefits. Furthermore, these recommendations come to us with world-wide scientific documentation that promises improved health and the reduction of risk in developing heart disease, cancer, and other degenerative diseases.
REFERENCES
D’Adamo, P.J., with C. Whitmey, Eat Right for Your Type. New York: G. P. Putnam’s Sons, 1996.
Kilpatrick, D.C., Pusztai, A., Grant, G., Graham, C., and Ewen, S.W., Tomato lectin resists digestion in the mammalian alimentary canal and binds to intestinal villi without deleterious effects. FEBS Lett, 1852:299-305, 1985.
Carvalho, M.R., and Sgarbieri, V.C., Relative importance of phytochemagglutinin (lectin) and trypsin-chymotrypsin inhibitor on bean (Phaseolus vulgaris L) protein absorption and utilization by the rat. J Nutr Sc Vitaminol (Tokyo), 44(5):685-96, 1998.
Hara, T., Mukunoki, Y., Tsukamoto, I., Miyoshi, M., and Hasegawa, K., Susceptibility of Kintoki bean lectin to digestive enzymes in vitro and its behavior in the digestive organs of mouse in vitro. J Nutr Sci Vitaminol (Tokyo), 30(4):381-94, 1984.
Aubry, M., and Boucrot, P., Comparative study on the digestion of radiolabelled vicilin, legumin and lectin of Pisum sativum in the rat. Ann Nutr Metab, 30(3):175-82, 1986. |
