The ‘blood-type’ diet is based on a popular book published in 1996, which has since sold over 7 million copies.2,3 The idea is that our blood group reveals something about our ancestral dietary habits, and matching our current eating to those habits help reduce disease risk. Those with blood group O, the hunter, are advised to eat a high-animal protein diet, blood type A, the agrarian, a mostly vegetarian diet, type B, the nomad, should eat...