For decades, the idea of eating according to your blood type has attracted attention. The theory suggests that people with types A, B, AB, or O have different nutritional needs. It became especially popular after a 1990s book claimed that each blood type evolved alongside a specific diet.

According to the theory, people with type O should eat more protein, while type A should focus mainly on plant-based foods. Type B diets often include dairy, meat, and vegetables, while type AB is encouraged to combine elements of the A and B plans. These recommendations have gained millions of followers despite limited scientific support.

Research, however, has not found strong evidence that blood type determines which diet is healthiest. Studies have not shown a clear health advantage from choosing foods based specifically on blood type. Some people say they feel better or lose weight while following these diets, but the benefits may come from eating more nutritious foods rather than from matching food choices to blood type.

Most blood type diets encourage whole foods, fruits, vegetables, and fewer processed foods and added sugars. Those changes can support better health for many people regardless of their blood type. As the original article notes, “These changes can improve health for almost anyone, regardless of their blood type.”

Blood type remains important for medical reasons, including blood transfusions and pregnancy, and it may be associated with certain disease risks. However, current evidence does not show that it determines the foods a person should eat. A balanced diet, healthy lifestyle, and individual nutritional needs remain more important than following a blood-type-based diet alone.