Thursday, November 4, 2010

#94: Peter D'Adamo

Food woo is potent stuff, and Peter D’Adamo is one of the most influential. Now, there is some evidence that his suggestions are, indeed, partially founded on Eastern (more closely Japanese) superstition (many remedies that claim such background are not), though it must, for obvious reasons, be a relatively new kind of superstition. The Eastern connection does, of course, not make his crackpottery more likely to be correct.

So what’s D’Adamo’s thing? D'Adamo's schtick is the Blood Type Diet (a.k.a. blood type astrology), in which the members of each of the four main blood type groups are assigned their own regimen of foods to consume and avoid. D’Adamo’s book, Eat Right 4 Your Type, was on the bestseller lists for a long time, despite (or, the cynical may suspect, because of) a complete lack of scientific evidence to support the central idea, namely that our body's immune system reacts differently to different foods, and tht those reactions are determined by the various antigens specific to the blood types. Apparently he is putting a lot of effort in capturing the Japanese market, as seen from his website.

Throughout his books D'Adamo cites the works of various biochemists and glycologists who have actually researched blood groups, implying that their research supports his ideas. The consensus among dieticians, physicians, and scientists, however, is that the theory is unsupported by scientific evidence. Remember that the Galileo gambit is a fallacy, if you were ever attempted to go down that route.

The wikipedia article is rather overly evenhanded. A more neutral and comprehensive evaluation is found here. (It might, by the way, look like the idea was dreamed up by his father, a naturopath named James D’Adamo – it is not quite clear).

His self-written biography is here.

Diagnosis: Frighteningly common type of crackpot who confuses anecdotal evidence and confirmation bias with science. Some of his advice may actually be harmful, so he must be considered moderately dangerous.

He is of course not alone in peddling this kind of woo. Obstetrician-Gynecologist Steven M. Weissberg, M.D., and Joseph Christiano, a personal fitness trainer, have co-authored a book making similar claims – the slogan being “You are what you eat, but you should ‘EAT WHAT YOU ARE.’ This means each of us should eat the optimal diet compatible with our blood type.” As with D’Adamo’s work, theirs is backed up by a multitude of anecdotes and tenuous correlations.


  1. Looks like we've drawn the attention of one of our entries here

    I suppose I should recommend readers to consult D'Adamo's blog for an erudite takedown of the claims made in this blogpost.

  2. There may be a lack of evidence to support his blood type diet theory, but there is a lack of evidence to support strong rebuttal as well. Hence it begs the question on some people's minds is that why is there a lack of clinical trials published? I mean someone supposedly influential making such claims cannot be left scientifically unchallenged. Do any dieticians have anything to hide ?

    There are even claims circulating that the oldest blood type is linked to Celiac Disease and gluten sensivity due to the fact that our ancestors thrive on primarily meat alone and not grains. Again no clinical trials ? Go ahead and search NIH or other journals, bet you'd find any.

  3. "but there is lack of evidence to support strong rebuttal as well".

    Maybe, but it is sort of missing the point (and d'Adamo himself missed it with flying colors). The reason there are few clinical trials published is presumably because no one has come up with any plausible mechanism for how blood type could affect nutritional uptake or anything (d'Adamo himself garbles the mechanisms and gets the historical narrative spectacularly wrong).

    The real point, however, that justifies concluding that d'Adamo is a crackpot and a loon is not that he is wrong. It is that he back in the 1990s published detailed guidelines (some of the advice demonstrably dangerous, even) on how to align your diet to your bloodtype, without having a shred of evidence for any of it. Even if later trials were, by some cosmic coincidence, to actually prove him right, it wouldn't alter the quackish behavior. A responsible non-crank would have formed a hypothesis, and then tried to test it - not published the unsupported hypothesis as if it were a well-supported and justified claim, and with extravagant, detailed recommendations. Heck, even if the hypothesis had been intuitively plausible, any respectable scientist with any shred of integrity would still have treated it as such - a hypothesis; we all know that even the most plausible-sounding hypotheses drawing on the most plausible causal mechanisms (which d'Adamo's certainly didn't) will generally turn out to be wrong.

    d'Adamo, however, didn't care then, and he doesn't care now. He has his fixed belief, and I betcha no amount of clinical trials, whatever they'd say, would change d'Adamo's (or his followers') beliefs about the matter.

    So no, I have no strong rebuttal (though some of the sources linked to do, and may direct one further to such rebuttals); neither am I a medical expert. To assess a hypothesis you will need to be; to recognize typical crackpot behavior you don't necessarily need to be.

    As for the possibility of a conspiracy theory, well, maybe this may help? It may be that d'Adamo is influential (and he seems to be), but after all, so is Deepak Chopra or Barbara Brennan. There really is not point in testing all the incoherent drivel that fall out of their mouths - it is hard to find anything really testable there, and besides their followers wouldn't care. d'Adamo is certainly not as far out as these two, but the reasons for a dearth of clinical hypotheses may still be the same. Without a plausible mechanism, and without any (non-dubious) case studies supporting d'Adamo's claims, it does not seem worth the cost, especially since most of his claims would need to be tested separately ("do blood type As benefit from including more or less milk in their diet as opposed to a control group"? It requires a pretty large sample, significant effects on the control group's daily lives, and probably a very extensive time frame)

  4. this is why they have a program at Bridgeport University that he heads up called Generative Medicine where blood type polymorphisms are taught..You need to take him off your list