Guess what the biggest source of foodborne illness in California was between 1996 and 1998. Meat? Eggs? Contaminated water?

Nope. Try alfalfa and clover sprouts. According to a study in the Annals of Internal Medicine, which investigated six multi-county outbreaks of bacterial infections, some 600 confirmed case of disease and two deaths were associated with eating bean sprouts. During the study period, sprouts caused more outbreaks of E. coli 0157:H7 and Salmonella than any other food or source.

Seeds are believed to be the source of the bacteria, since they are put in a rotating drum, misted with warm water and left at room temperature in order to grow sprouts. Unfortunately, these conditions also provide a perfect incubator for bacteria. And because sprouts are typically eaten raw, the bacteria remain intact.

According to the U.S. Food and Drug Administration, sprouts should therefore be cooked in order to kill the bacteria. Because the bacteria can become internalized during sprouting, mere washing is not an effective means of sanitizing the produce.