Updated on 4/4/2005
In 2002 the FDA issued a health advisory warning consumers of the risks associated with eating raw sprouts due to an outbreak of E. coli associated with alfalfa sprouts. The advisory also included raw and undercooked mung bean sprouts.
I have long advised against eating bean sprouts raw because of toxins they contain that are only broken down by thorough cooking. (The toxin in alfalfa sprouts is canavanine, which can harm the immune system.) The problem for which the FDA issued its warning concerns outbreaks of foodborne illnesses stemming from the bacteria Salmonella or E. Coli. The symptoms these bacteria cause include diarrhea, nausea, abdominal cramping and fever, which can last for several days. While unpleasant, these infections generally aren't a great threat to healthy people but can be dangerous to children, the elderly and those with weakened immune systems.
Between 1995 and 1998 there were 35 outbreaks of foodborne illnesses in the United States affecting more than 1,200 people caused by Salmonella or E. coli due to consumption of raw bean sprouts. Incidentally, samples of both imported and domestic fruits and vegetables have also been found to be contaminated with Salmonella and E. coli. The best way to protect yourself from infection is to wash all fruits and vegetables thoroughly under running water and avoid cross-contaminating one food with another by washing your hands, utensils, and cutting boards after using them for one type of raw food and before using them again for another.
As for bean sprouts, don't eat them raw or lightly cooked. In the case of alfalfa, that means not eating them at all, since cooking turns the delicate sprouts to mush. According to the FDA not even homegrown sprouts can be safely eaten raw because many outbreaks have been due to contaminated seeds. If the bacteria are in or on the seeds, they can flourish during sprouting even under clean conditions. Insist that sandwiches and salads in restaurants and delis be served without alfalfa sprouts, and if and when you do eat other bean sprouts, make sure that they're thoroughly cooked.
Andrew Weil, M.D.