Blood Type Diet Debunked
Dr. Peter D’Adamo’s book Eat Right for Your Type makes the astounding claim that people with different blood types should eat different foods. Type O’s, for example, are supposed to be like the hunter and eat a lot of meat, whereas type A’s are supposed to eat less. A 2013 systematic review of the evidence supporting blood type diets was published in one of the world’s most prestigious nutrition journals. The researchers didn’t find any.
The researchers sifted through over a thousand papers that might shed some light on the issue, and none of the studies showed an association between blood type diets and health-related outcomes. They conclude that “there is currently no evidence that an adherence to blood type diets will provide health benefits, despite the substantial presence and perseverance of blood type diets within the health industry.”
Ten years earlier, the Journal of the Norwegian Medical Association released a number of papers that came out of a day-long scientific seminar held by the Norwegian Society for Nutrition. 40,000 copies of the Eat Right for Your Type had been sold in Norway, and so the researchers sought to determine whether blood type diets were visionary science or nonsense. They also concluded that they are nonsense.
The author of the blood type diet book responded to the review on his website, saying that “there is good science behind the blood type diet, just like there was good science behind Einstein’s mathematical calculations.” He says that if blood type diets were just tested in the right way, like how Einstein’s E=MC2 was, he would be vindicated. The reason we don’t see any studies on blood types and nutrition, he complains, is “because of little interest and available money.” But he’s sold more than seven million books. Why doesn’t he fund his own studies? That’s what the Atkins Corporation did.
In fact, he has! In 1996, he wrote, “I am beginning the eighth year of a ten year trial on reproductive cancers, using the Blood Type Diets … By the time I release the results in another 2 years, I expect to make it scientifically demonstrable that the Blood Type Diet plays a role in cancer remission.” OK, so that would be 1998. The results? Still not released, sixteen years later.
Good tactic, though, saying you’re just about to publish a study and banking that nobody would actually follow up. So in his sequel, he said he was currently conducting a “twelve-week randomized, double-blind, controlled trial implementing the Blood Type Diet, to determine its effects on the outcomes of patients with rheumatoid arthritis.” That was ten years ago.
As my Norwegian colleague bemoaned, “it is difficult not to perceive the whole thing as a crass fraud.”
So rarely are popular press diet books afforded such fact-checking. Kudos to these researchers. If only we had this 17 years ago when the book was on the bestseller list!
I have a few videos on popular diets, such as:
I wrote a book about low-carb diets, with the full-text now available for free at AtkinsFacts.org
Michael Greger, M.D.
PS: If you haven’t yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of Death, More Than an Apple a Day, and From Table to Able.