The book, Eat Right for Your Type, makes the astounding claim that people with different blood types should eat different foods. Type O's are supposed to be like the hunter and eat a lot of meat, whereas people with type A blood are supposed to eat less. A systematic review of the evidence supporting blood type diets was published in one of the world's most prestigious nutrition journals. 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 they found so outrageous is that the 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 tenants of blood type biology as absurd.
There should be no doubt that the author had practiced in Norway, as opposed to Connecticut, where 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 that your brains fall out: "it 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 specific diet."
I don't know how researchers have the patience to read these popular press books, but 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: “boy, does he have a good imagination.”
Is it any worse than people who believe their fate is determined by the stars? 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. Positive results reported by some individuals may well be due to a general improvement in diet and lifestyle (less fat and sugar, more fruits and vegetables, less smoking, more exercise). Look, anything that gets people to eat fewer doughnuts, I don't care if you say Martians said so.
This may get lost a bit in translation, but this 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 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.
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 the reason you don’t see any studies on blood types and nutrition is because of little interest and available money. He's sold more than seven 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." OK, so that would be 1998, and the results? Still not released.
Good 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 colleague bemoaned, "it is difficult not to perceive the whole thing as a crass fraud.”
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.