Researchers from the University of Toronto
(U of T) have found that the theory behind the popular blood type diet – which
claims an individual's nutritional needs vary by blood type – is not valid. The
findings are published this week in PLoS One.
"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," said El-Sohemy.
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.
is the blood type diet?
The 'blood-type' diet was popularised in
the book Eat Right for Your Type, written by naturopath Peter D'Adamo. The
theory 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
According to the theory, 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
Just no evidence
The U of T researchers 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.
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." 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 it.
Blood-type diets not backed by science
The blood type diet – the facts