Despite numerous attempts by many people to let Dr. Andrew Weil know that his traditional criticisms of the Blood Type Diet have no basis in fact, he still insists on peddling his absurd take on my work. In a recent interview for a Canadian website, Weil repeats the same criticisms he has used for the last ten years --despite the fact that they are as inaccurate and ignorant of the basic facts now as they were a decade ago.

Among other things, Dr. Weil says:

This is nonsense. I know of no evidence suggesting that prehistoric people ate diets related to their blood types. The studies D'Adamo cites have been published only by him and not in any scientific journals. By the way, dogs and other animals have blood types similar to those of humans. It would come as unwelcome news to some dogs that they should be vegetarians.

This tone suggests to me that Dr. Weil has not actually read any of my books.

I've never suggested that prehistoric people ate diets according to their blood types. No doubt they should have, but how would they have known? The blood groups were not discovered until 1900.

I have suggested that the variations in our different digestive physiologies stem from adaptations over time to changes in diet that were in part coded by the immunology that governs the gut. And that this immunology is significantly under the influence of ABO blood type.

Dr. Weil avoids or just plain neglects the physiologic links between digestion and ABO blood types. This lets him parody my theory as some sort of 'caveman-fiction.' The effects of secretor status on immune and metabolic function; the connection between lectins and allergies; the influence of blood type on intestinal enzymes; links between stomach hydrochloric acid levels and gut bacteria; the fact that the very foods we eat have 'blood types' --all of this receives no mention.

These findings and facts are part of over 7,000 peer-reviewed studies on blood groups published in the medical literature over the last century. Now, I know that allopathic (MD) education does not teach any of this, so I don't blame Weil for being initially uninformed. Everyone has got to start somewhere. However he does not exhibit any curiosity on the subject nor a desire to investigate it any further. If he'd have contacted me, I'd have probably shared them with him. Instead we're left with the rather smug assumption that since he's never heard of any of this, it must not exist.*

Folks, that is an attitude that they usually do teach you in allopathic medical school.

I've always gotten a kick out of his "Well, animals don't eat right for their type" argument. If he knew the species genetics of ABO blood groups he might be surprised to learn that the ABO gene locus resides on different chromosomes in the various species. In hogs for example, having type O blood gives you a full coat of black hair. By Dr. Weil's account, every human who is type O blood should also have black hair. Dogs, by the way, are a very cancer prone species, and do fare much better on something other than an exclusively carnivorous diet.

Sigh.

The late Arthur C Clarke said it best in his First Rule of Scientific Prediction:

When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.

* Dean Ornish repeats a similar mantra to audiences that he is 'unaware of any studies linking heart disease to blood types', when even the most cursory of searches on MEDLINE would show 200+ articles since 1966 (and probably over 300 from 1950).