Blood Type Diet Debunked

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

It was Adolf Hitler who coined a propaganda technique he called, “the big lie,” arguing that people may be more likely to believe “colossal untruths,” because “they would not believe that others would have the impudence to distort the truth so infamously.” So, “in the big lie there is always a certain force of credibility.”

The book Eat Right for Your Type makes the astounding claim that people with different blood types should eat different foods. Type Os are supposed to be like the hunter, and eat a lot of meat, whereas people with type-A blood are supposed to eat less. In one of the world’s most prestigious nutrition journals, a systematic review of the evidence supporting blood-type diets was published. They didn’t find any.

“Diets based on the ABO blood group system have been promoted over the past decade…[but] the evidence to support the effectiveness of [such] diets [had evidently] not previously been assessed in the scientific literature.” Actually, in the Journal of the Norwegian Medical Association, there were a number of papers that came out of a day-long scientific seminar held by the Norwegian Society for Nutrition. Hard to believe they would even take the time, but evidently 40,000 copies of the book had been sold in Norway, and so, good for them. They sought to determine “Blood type diets: visionary science or nonsense?” And, they concluded: nonsense.

What was so outrageous is that “[t]he blood-type diet is promoted and justified [in the book] by [supposed] scientific arguments,” yet the author takes “no pains to prove” his ideas—just presenting them “simply as facts,” taking advantage of people’s ignorance of biology.

His arguments sound scientific, and he uses lots of big words. But, he displays a fundamental misunderstanding of the science, describing the book’s understanding of some basic tenets of blood-type biology as “absurd.” “There should be no doubt that [had the author]…practiced in Norway [as opposed to Connecticut], he would be in violation of the “so-called Quack [Law].”

The book cites the work of blood-type biochemists, but if you ask the actual experts, as scientists, they say they obviously have to keep an open mind, but not so open your brains fall out: “[I]t must be stated that an ‘open mind’ should not extend to some of the non-scientific literature where there are books on the ABO [blood-type] system of pure fantasy. The most recent and incredulous of these claims [that] individuals of each ABO blood type must subscribe to a [particular] diet.”

I don’t know how researchers have the patience to read these popular press books, but it can “lead to an appreciation of the ridiculous aspects of the many ignorant and preposterous claims.”

“So, what should the overall assessment of [this] work be?” The nicest thing you can say about the book is: he does have a good “imagination.”

Is it any worse than people who believe their fate is “determined by” the stars, though? Well, yes, because astrologists aren’t telling a third of the population to go out and eat organ meats.

The diet is not as bad as some. “[P]ositive results reported by [some] individuals may well be due to a general improvement [in health] in diet and lifestyle (less fat and sugar, more fruits and vegetables, less smoking, [and] more exercise).” Look, anything that gets people to eat fewer doughnuts.

But though this may get lost a bit in translation, a professor of laboratory medicine at the Norwegian University of Science’s analysis concluded that the author’s “learning must be considered junk and without scientific foundation.”

What did the new review find? They sifted through over a thousand papers that might shed some light on the issue, and “[n]one 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.”

The author responded to the review on his website, saying that there’s “good science behind the blood type diet, just like there was good science behind Einstein’s mathematical calculations,” and that if blood-type diets were just tested in the right way, just like Einstein’s E=MC² , he would be vindicated—complaining that “you don’t see any studies on blood types and nutrition [because of] [l]ittle…interest and…available money.” He’s sold over “7 million” books! Why doesn’t he fund his own studies? That’s what the Atkins Corporation did.

And, the answer is: 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.” Okay, so that would be 1998, and the results? Still not released, 16 years later.

Clever tactic, though, saying you’re just about to publish, 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 colleagues bemoaned, “it is difficult not to perceive the whole thing as a crass fraud.”

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• L Cusack, E De Buck, V Compernolle, P Vandekerckhove. Blood type diets lack supporting evidence: A systematic review. Am J Clin Nutr 2013 98(1):99 - 104.
• J Wang, B García-Bailo, D E Nielsen, A El-Sohemy. ABO genotype, 'blood-type' diet and cardiometabolic risk factors. PLoS ONE 2014 9(1):e84749.
• A Hitler, J V Murphy. 1981. Mein Kampf. London: Hurst and Blackett. Print.
• HM Melter, M Haugen, KC Haavardsholm, KB Hagen, HE Heier, AMB McKellep, H Glørstad, A Tandberg. Blodtypedietten – visjonær vitenskap eller tull? Tidsskrift for Den norske legeforening. 2002 14(122):1402-5.
• T Moen. Blood Type Diet-- Science or Fantasy? Tidsskrift for Den norske legeforening. 2011 3(121):355-8.
• MJ King, ed. Human Blood Cells: Consequences of Genetic Polymorphisms and Variations. International Blood Group Reference Laboratory. Imperial College Press. 2002.
• D Larhammar. Fakes and Frauds in Commercial Diets. Scandanavian Journal of Nutrition. 2005 49(2):78-80.

• Albert Einstein
• Atkins diet
• blood type diet
• exercise
• fat
• fruit
• meat
• nutrition myths
• rheumatoid arthritis
• smoking
• sugar
• vegetables