Favism

Eating fava beans is the cause of a serious disease, favism, in people who have an inherited deficiency of a particular enzyme. Most victims are children who live in the southern Mediterranean and Middle East, or whose ancestors came from that region. When they are exposed to two unusual amino-acid relatives (vicine and convicine) in the beans and in the flower pollen, their bodies metabolize these chemicals to forms that damage their red blood cells and cause serious, sometimes fatal anemia. The enzyme deficiency also turns out to suppress the growth of the malaria parasite in red blood cells, so it may actually have been an advantageous genetic trait before malaria was brought under control.