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Blood Type Diet Theory Debunked

The diet theory that claims our nutritional needs vary by blood type is not valid, according to researchers at the University of Toronto. The team found that the associations they observed between each of the four blood type (A, B, AB, O) diets and the markers of health are independent of the person’s blood type. The study was published in January 2014 in the journal PLoS One.

The blood type diet was popularized in the New York Times best sellerEat Right for Your Type”, written by naturopath Peter D’Adamo and published in 1997. The author claimed that adhering to a diet specific to your blood type can improve health and decrease risk of chronic illness such as cardiovascular disease. The current study proves this to be false.

A release from the university quotes senior author Dr. Ahmed El-Sohemy, associate professor and Canada Research Chair in Nutrigenomics at the University, as saying, “Based on the data of 1,455 study participants, we found no evidence to support the ‘blood-type’ diet theory. 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.”

The U of T research corroborates the results of a 2013 of a comprehensive review published in the American Journal of Clinical Nutrition that found no evidence to support the blood-type diet and called for properly designed scientific studies to address it. El-Sohemy and colleagues responded to the call for further research. “There was just no evidence, one way or the other," El-Sohemy said. "It was an intriguing hypothesis so we felt we should put it to the test."

The team took an existing population of mostly young and healthy adults who provided detailed information about their usual diets and provided fasting blood that was used to isolate DNA to determine their ABO blood type and the level of cardiometabolic risk factors, such as insulin, cholesterol and triglycerides. Diet scores were calculated based on the food items listed in “Eat Right for Your Type” to determine relative adherence to each of the four blood-type diets.

"We can now be confident in saying that the blood type diet hypothesis is false,” said El-Sohemy.

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