The richest source of selenium--with 30 times more than any other food--is the Brazil nut! It takes only one or two to get the entire daily Recommended Dietary Allowance for selenium. But if you're nuts about Brazil nuts, beware: They're so stuffed with selenium that eating too many on a regular basis--a big handful every day--could lead to selenium toxicity. On the other hand, a Brazil nut or two a day--on top of a normal diet--is reasonable. Selenium acts in our bodies as a key player against unstable molecules that may cause cancer and heart disease.