The theory behind the blood-type diet is false, according to new new research.

The diet, based on Peter D’Adamo’s best-selling book Eat Right for your Type, claims that an individual’s nutritional needs vary by blood type.

But researchers at the University of Toronto disagree after a study that looked at information from 1,444 people.

Ahmed El-Sohemy, an associate professor and chair in nutrigenomics at the University of Toronto and senior author of the study said: “Based on the data of the 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,” he said.

The book is an  international bestseller

Researchers discovered the associations they observed between each of the four blood-type (A, B, AB, O) diets and the markers of health have nothing to do with the person’s blood type.
The theory is that the ABO blood type should match the dietary habits of our ancestors and people with different blood types process food in different ways. Which means, according to the book, 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 a New York Times best-seller that has been translated into 52 languages and sold over 7 million copies.

What happened in the study?
The research looked at 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 levels of heart health 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.

El-Sohemy says that a previous lack of scientific evidence doesn’t mean the diets didn’t 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.”

Similarly, a comprehensive review published in the American Journal of Clinical Nutrition found no evidence to support the blood-type diet.