If you tried the martini diet, the tapeworm diet and going gluten-free, science has bad news; the popular blood type diet isn't going to work any better for you.
The 'blood-type' diet was popularized in the book "Eat Right for Your Type", written by 'naturopath' Peter D'Adamo. The hypothesis behind the diet is that the ABO blood type should match the dietary habits of our ancestors and people with different blood types process food differently. According to that, individuals adhering to a diet specific to one's blood type can improve health and decrease risk of chronic illness such as cardiovascular disease. The book was unsurprisingly a New York Times best-seller and has been translated into 52 languages and sold over 7 million copies.
The researchers behind the study 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.
‘Blood-Type’ diet (A). Diet score distribution for each ‘Blood-Type’ diet (B). doi:10.1371/journal.pone.0084749
"Based on the data of 1,455 study participants, we found no evidence to support the 'blood-type' diet theory," said the senior author of the study, Dr. Ahmed El-Sohemy, Associate Professor and Canada Research Chair in Nutrigenomics at the University of Toronto. "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."
Researchers 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.
El-Sohemy says that a previous lack of scientific evidence doesn't mean the diets didn't work - but that is what evidence means. If it isn't shown to work, it's homeopathy or acupuncture or anything else until it is shown to work. "There was just no evidence, one way or the other. It was an intriguing hypothesis so we felt we should put it to the test. We can now be confident in saying that the blood type diet hypothesis is false."
Last year, a comprehensive review published in the American Journal of Clinical Nutrition found no evidence to support the 'blood-type' diet and called for properly designed scientific studies to address the issue.