Study Finds the ‘Blood Type Diet’ Doesn’t Work

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Another fad diet bites the dust. A new study finds that the once-popular blood-type diet, which is based on the theory that blood type dictates which foods you should and shouldn’t eat, isn’t grounded in science. Researchers at the University of Toronto analyzed nearly 1,500 adults and determined that eating according to blood type has no impact on health.

This diet was introduced in 1996 in the book Eat Right for Your Type by Peter D’Adamo, which sold some 7 million copies. D’Amano proposes that people with blood types A, B, AB, and O process foods differently. In the book, he lays out restrictive meal plans – such as eliminating grains or going vegetarian – according to each blood type, which supposedly helps reduce risk of heart disease, diabetes, asthma, stress, cancer, and more.

But, as many doctors and dietitians had suspected, this style of eating doesn’t hold up in the lab. “There is absolutely no science to back up any correlation between blood type and which foods are best for you,” says Joan Salge Blake, RD, a health sciences professor at Boston University and spokeswoman for the Academy of Nutrition and Dietetics. “What we do know, based on lots of science, is that a well-balanced, heart-healthy diet can reduce the risk of cardiovascular disease, type 2 diabetes, heart attack, stroke, and certain cancers.”

The other big problem with the blood-type diet, according to Salge Blake, is that eliminating certain foods unnecessarily can leave you starved for much-needed nutrients. “According to this theory, if you have a certain blood type, you should eliminate wheat,” she says. “But by cutting out wheat, you may be lowering your intake of fiber and vitamin B.”

Salge Blake agrees that different foods affect the blood, which impacts whole-body health. For instance, she says decreasing saturated fat will help lower LDL, or bad cholesterol, which reduces the risk of cardiovascular disease. But that’s true no matter what type of blood you have.