Many years ago I criticized a very popular but ridiculous book that said people should follow different diets depending on their blood types. Now, finally, a study of 1,455 mostly young and healthy adults shows that there is no relation whatever between blood type and diet-linked heart attack risk indicators such as insulin, cholesterol or triglycerides (PLoS One, January, 2014).
Study participants provided detailed information about their usual diets and had blood drawn for DNA tests to determine their ABO blood type, as well as tests for levels of insulin, cholesterol and triglycerides. They were assigned to the diet that corresponded with their blood type. Then the authors calculated diet scores based on food items listed in the book, Eat Right for Your Type to see how well the people adhered to each of the four ‘blood-type’ diets. The study’s lead author, Dr. El-Sohemy, concluded that “The way an individual responds to any one of these diets has absolutely nothing to do with their blood type and has everything to do with their ability to stick to a sensible vegetarian or low-carbohydrate diet.”
Eat Right for Your Type was a New York Times best-seller that was translated into 52 languages and sold more than seven million copies, even though there was no scientific evidence that blood type has anything to do with which foods a person should eat. According to the book’s author, if you eat the foods he said were dictated by your blood type, you would protect yourself from heart disease and other illnesses. The author failed to tell his readers that the book was based on his opinion and that most members of the scientific community disagreed with him. Last year, another article published in the American Journal of Clinical Nutrition also found no evidence of any health benefits from ‘blood-type’ diets (Am J Clin Nutr, July 2013). However, even though there is no known link between diet and blood type, the four diets proposed by the author are healthful diets and if you follow any one of them faithfully, you are likely to lose weight. They all follow the simple rule of “take in fewer calories than you burn.”