New Study Debunks Plant-based Diets Tied to Blood Type

A new analysis published in the Journal of the Academy of Nutrition and Dietetics debunks the idea blood type is linked with the effects of a plant-based diet.

“Risk of cardiovascular disease is lower in individuals with blood type O and increased in individuals with blood type A, compared with those in other blood groups,” the authors wrote in their abstract. “However, little evidence is available regarding whether individuals with different blood types benefit from different diet recommendations.”

The study design was that of a secondary analysis of the metabolic effects of a low-fat plant-based diet on a group of adults with body mass index (BMI) between 28 and 40. They were assigned to either a vegan group (n=122) or to a control diet (n=122) for a period of 16 weeks. Blood types of the participants were evaluated and cataloged. A total of 68 participants completed the vegan arm of the study, as dropouts and exclusions decreased the number of completed cases. The primary outcome was body weight, BMI, fat mass, visceral adipose tissue volume, blood lipid levels, fasting plasma glucose levels, and glycated hemoglobin concentrations.

The authors reported that baseline mean body weight, BMI, fat mass, visceral fat volume, and HbA1C concentration did not differ between the blood type groups. Changes in lipids were also similar between blood type groups. Changes in fat mass and VAT were like those of body weight and did not differ between blood type groups.

“After 16 weeks on a low-fat vegan diet, no significant differences were found in any of the cardiometabolic changes between blood type groups,” the authors wrote. “Although the intervention diet was similar to that recommended by D’Adamo (edit: had written a book prescribing blood-type-specific diets), for individuals with blood type A and specifically recommended against for those with type O, there were no associations between these blood types and the outcomes of the dietary intervention.”

Researcher Neal Barnard, MD, president of the Physicians Committee for Responsible Medicine (authors of the study), said that the results do nothing to take away from the notion that plant-based diets are still healthy no matter the blood type.

“While the blood type diet says that a plant-based diet should be better for blood type A and less so for blood type O, it turned out to be beneficial for people of all blood types, and there was no evidence that meaty diets are good for anyone,” Dr. Barnard said in a press release. “Our research shows that all blood types benefit equally from a vegan diet based on the consumption of fruits and vegetables, legumes and whole grains, looking specifically at weight loss and cardiometabolic health in overweight adults.”