ABO blood group system During the 1930s, connecting blood groups to personality types became popular in Japan and other areas of the world. Studies of this association have yet to confirm its existence definitively. Other popular but unsupported ideas include the use of a blood type diet, claims that group A causes severe hangovers, group O is associated with perfect teeth, and those with blood group A2 have the highest IQs. Scientific evidence in support of these concepts is nonexistent. ABO blood group system The ABO blood group system is used to denote the presence of one, both, or neither of the A and
Blood type diet Blood type diet The blood type diets are fad diets advocated by several authors, the most prominent of whom is Peter J. D'Adamo. These diets are based on the notion that blood type, according to the ABO blood group system, is the most important factor in determining a healthy diet, and each author recommends a distinct diet for each blood type. The consensus among dietitians, physicians, and scientists is that these diets are unsupported by scientific evidence. In what was apparently the first study testing whether there was any benefit to eating the "right" diet according to one's blood type,