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Blood Type Diet: Fact or Fiction?

Popular nutritional diet method examined by researchers…. 

The blood type diet outlined in the book Eat Right 4 Your Type written by Peter D’Adamo advocates specific diets based on blood type. For example, those in blood group O should eat a diet high in proteins, those in blood group A should have a diet that emphasizes vegetables over red meat, while those in blood group B are able to thrive on dairy products. This is because, according to D’Adamo, group O people are believed to have ancestral ties to those in the hunter-gatherer era while group B has ties to nomadic tribes and group A have ties to agrarian societies. His book was first published in 1996 and has since sold over 7 million copies, making the New York Times bestseller list numerous time. This diet has been subjected to controversy because of its lack of supporting scientific evidence. Researchers then set on a study to examine the association between blood group diets and biomarkers of cardiometabolic health.

A study was performed at the University of Toronto in which 1,455 subjects aged 20 to 29 participated in a cross-sectional examination between October 2004 and December 2010. Their dietary intake was assessed using a 196 question semi-quantitative food frequency questionnaire. To quantify adherence to the different blood group diets, subjects received a positive point for consuming one serving of a recommended food item while receiving a negative point for consuming one serving of an item on the list of foods to avoid. Foods that were considered neutral on the questionnaire did not contribute to the final score. The subjects were then grouped based on their scores for each diet. Those with the highest scores represented those whose diet that most closely resembles the corresponding blood group diet.

The findings of this study shows that although adherence to blood group diets are associated with favorable effects on cardiometaboilc risk factors, they are not dependent on the subject’s blood type. For example, adherence to a blood group A was associated with a lower BMI, blood pressure, triglycerides, and waist circumference, while a blood group O diet was associated with lower triglycerides only. However, these associations are not due to the nature of the subject’s blood type.

This particular study shows that there is no scientific evidence to show that the blood group diets work when performed on a person with a matching blood type. However, this is not to say that the diets itself do not work. It is not surprising that a diet rich in vegetables and low on meat products promotes favorable values for cardiometabolic risk factors. There is just no scientific evidence to associate particular diets to particular groups of people. Any of these diets have been met with favorable effects on particular biomarkers of cardiometabolic risk factors. In short, the way an individual responds to these diets has nothing to with their blood type, but rather their ability to stick to a sensible diet.

Accepted for publication in the Endocrine Society’s Journal of Clinical Endocrinology & Metabolism (JCEM).