Richard G. Petty, MD

Diet and Blood Types

One of my earlier posts entitled “What in Your Blood?” elicited a most interesting and important question from a reader:

“Does any of this have to do with the research that Dr. Peter D’Adamo has in his "Blood Type Diet" book? I have had clients tell me diseases and pains vanished when they followed his diet, while others had no effect. I would be interested in hearing your take on it all.”

This is a great question that gives me the opportunity to comment about this whole issue. I think that many of us have made similar observations to the reader who asked the question.

For people not familiar with this theory, D’Adamo’s notion is that our ancestors originally all had type O blood group, and that the appearance of agriculture was associated with the appearance of type A blood group, and then as recently as 10,000 B.C.E. – A.D. 1000, types B and AB started to evolve.

In this scheme, people with Type O blood group are the descendents of Hunters, the dominant, hunter-caveman types that require meat in their diet and should avoid wheat and beans. They are supposed to be most likely to suffer from asthma, hay fever, and other allergies. People with Type A blood are originally the Cultivators, and they should eat a vegetarian diet since they are predisposed to heart disease, cancer and diabetes; Type B blood group people were allegedly Nomads, and are dairy-eating omnivores who are susceptible to chronic fatigue and autoimmune disorders, such as systemic lupus erythematosus and multiple sclerosis. The rare individuals who have the AB blood group require a mixed diet, but should avoid chicken. They are supposed to be at risk of heart disease, cancer, and anemia, but tend to have the fewest problems with allergies. So D’Adamo decided that we should eat according to our blood types.

Like a lot of simple models, it is attractive and can be seductive. Yet the underlying concepts are deeply flawed. There are some weak associations between some blood groups and some physical ailments: to name just two, blood type A and coronary artery disease, and type O and gastric ulcers. That second one we now understand: people with blood group O are not able to mount a strong immune response to the usual causative organism: Helicobacter pylori. I did a literature review and dug up over 700 research papers on the subject of blood groups, disease and lectins (the adhesion molecules found, amongst other places, on red blood cells). There was nothing whatsoever to confirm D’Adamo’s claims. Indeed I think that some of his claims are potentially risky. Few people would agree with the idea of feeding some people high fat diets, and the theory takes no account of ethnic differences in food tolerability. For instance the high rates of insulin resistance amongst most people of Indian heritage, or the dairy intolerance common in much of the Asia-Pacific rim.

D’Adamo’s theory of blood group evolution is not correct. Far from having developed new blood groups with the arrival of agriculture, there is solid molecular evidence that the different blood groups were already present at least 5 million years ago. Gorillas and chimpanzees possess similar blood groups. One of the scientists quoted on the D’Adamo website is Winifred Watkins, who was one of the team that first described the structure of the molecules determining blood group types. She was only 29 at the time, and later she became a Fellow of the Royal Society and a mentor of mine. She passed away about three years ago. She was the person who first told me about the evolution of blood groups, and there’s now a fair bit written about it. The last great African Diaspora occurred long before the development of agriculture, and the migrants took their diverse blood groups with them. That is one of the ways in which migration patterns have been tracked. So there is no link between blood groups and “professions.” It is still possible that there is some other arcane link between optimum nutrition and blood groups, but it is now ten years since D’Adamo’s book came out, and we have to ask why there is no published research to support the claims. His website contains a lot of references to research papers on blood groups. Many are quite old, and there is no critical evaluation of the papers.

Yes, some people will benefit from any kind of diet or intervention, which is why some of your clients have benefited, but the predictive value of the four major blood group types is clearly very low.

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About Richard G. Petty, MD
Dr. Richard G. Petty, MD is a world-renowned authority on the brain, and his revolutionary work on human energy systems has been acclaimed around the globe. He is also an accredited specialist in internal and metabolic medicine, endocrinology, psychiatry, acupuncture and homeopathy. He has been an innovator and leader of the human potential movement for over thirty years and is also an active researcher, teacher, writer, professional speaker and broadcaster. He is the author of five books, including the groundbreaking and best selling CD series Healing, Meaning and Purpose. He has taught in over 45 countries and 48 states in the last ten years, but spends as much time as possible on his horse farm in Georgia.

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