Some people believe your blood type -- A, B, AB, or O -- is a good predictor of what your personality traits are, including whether or not you'll be introverted or extroverted and even how well you'll do in the romance department. In fact, in 2011 Japanese politician Ryu Matsumoto blamed the offensive remarks he made after the devastating earthquake and tsunami on his blood type, which is cold and impulsive type B [source: Reuters].
In the mid-'90s, the Eat Right for Your Type diet encouraged Americans to be healthier by eating a menu determined by your blood type. For example, O blood types are an "old" blood line and should focus on ancient eating habits that include meats and fish; wheat, on the other hand, should be avoided because it makes O types sluggish and bloated. Type A? Try an A-for-agrarian (vegetarian) diet. We could go on, but there's no evidence that following such a diet is at all beneficial for good health and decreased risk of chronic illness [source: Cusack].