Asked by: Charlotte McGuinness, London
In 1996, a naturopath named Peter D’Adamo argued that eating a diet ‘designed’ for your blood type (O, A, B, or AB) meant that your body would digest food more efficiently, and you would lose weight and prevent disease. The diet has proven immensely popular, with millions of followers. Blood is indeed involved in digestion: the digestive process occurs in the gut, and the nutrients are absorbed and transported by blood to the various cells and organs.
There is, however, zero evidence that the different macronutrients (glucose, amino acids and fatty acids) react to the four blood types in any appreciably different way. Our individual biology may well influence how we respond to food, but not our blood type. There is no truth to this diet.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun facts.