Simply eating more healthfully, and not following menu guidelines based on blood type, is apparently the real secret behind a popular diet based on blood type, researchers in Canada say.

A scientific team from the University of Toronto has determined the theory behind the so-called blood-type diet -- which claims an individual's nutritional needs vary by blood type and has recently gained several high-profile celebrity fans, in addition to widespread interest -- is not valid.

"Based on the data of 1,455 study participants, we found no evidence to support the blood-type diet theory," Ahmed El-Sohemy, the study's senior author, an associate professor and Canada Research Chair in Nutrigenomics at the university, said in a release.

"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 added

The findings were published this week in the journal PLoS One.

El-Sohemy and his colleagues discovered the supposed links they observed between each of the four blood-type diets (for types A, B, AB and O) and the indications of good health were actually independent of people's blood types.

The blood-type diet was popularized in the book Eat Right for Your Type, which was written by naturopath Peter D'Adamo.

The theory behind the blood-type eating approach is that people with different blood types process food differently.

As such, individuals who follow a diet specific to their blood types can improve their health and decrease the risk of chronic illnesses, such as cardiovascular disease.

The book, which suggested those with A, B and O types should match the dietary habits of earlier humans, has been New York Times best-seller that's sold over 7 million copies worldwide and has been translated into 52 languages.

The researchers took an existing population of mostly young and healthy adults who provided detailed information about their usual diets and also fasted before giving blood samples, which were used to determine their blood types, isolate DNA and determine risk factors, such as their levels of insulin, cholesterol and triglycerides.

The diet scores of the study participants were calculated based on the food items listed in Eat Right for Your Type, showing apparent connections between the health of participants and their adherence to their individualized blood-type diets.

El-Sohemy said the new data left no doubt that the blood-type diets don't deliver on their health claims.

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

In 2013, a comprehensive review published in the American Journal of Clinical Nutrition found no evidence to support the blood-type diet. That piece called for additional scientific studies to futher examine the effectiveness of the diets.