Since July 1999, when the U.S. Food and Drug Administration issued its first warning about the safety of raw sprouts, there has been a growing controversy about this issue. On the one hand, sprouts have some well-documented health benefits. For example, they can work better than antibiotics in preventing stomach ulcers related to overgrowth of the bacterium Helicobacter pylori. They can also help prevent stomach cancer in relationship to this same set of events.U.S. Food and Drug Administration (FDA) Warning
At the same time, however, ingestion of radish sprouts contaminated with the bacterium E. coli O157:H7 caused the death of 17 persons in Japan in 1996, and was also responsible for illness in over 6,000 persons. This outbreak factored into the U.S. Food and Drug Administration's decision in 1999 to issue a warning about the dangers of eating raw or lightly cooked sprouts and recommending cooking of all sprouts to lower risk of infection. The FDA specifically mentioned alfalfa, clover, and radish sprouts in this initial warning. In 2002, it focused on mung bean and alfalfa sprouts in a renewed warning about consumption of these foods.
Since 1995, the Centers for Disease Control (CDC) in Atlanta, Georgia have reported 15 salmonella outbreaks of salmonella poisoning and two outbreaks of E coli O157:H7 poisoning in association with consumption of raw sprouts. In its renewed warning in 2002, the FDA referred to these outbreaks as further reasons to cook sprouts before eating.
The process of preparing, processing, and handling of raw sprouts does not appear to be the main source of potential contamination with Salmonella or E. coli bacteria. Apparently, this contamination usually involves the status of the seeds which are being sprouted. For example, use of improperly composed manure or fertilizers during seed production appears to be a likely source of bacterial contamination since bacteria-related outbreaks have usually been associated with specific seed lots (batches of seeds that can be traced through specific lot numbers). Improperly cleaned seed harvesting or processing machinery, use of untreated water during seed production, or water runoff from animal production facilities into seed production facilities can all be related to seed contamination. Once seeds have become contaminated, sprouting can make things worse, since the moisture and heat involved with sprouting can also be conducive to bacterial growth.
Even though it's the seed production step (as opposed to the sprouting step) that seems most implicated in sprout contamination, it's certainly not impossible for contamination to take place when the seed sprouting is carried out in a fully sanitary way.
If you do decide to keep raw sprouts in your Healthiest Way of Eating for their health benefits, here are some steps you can take to help make sure that they are safe to eat:
Anonymous. (1999). Microbiological safety evaluations and recommendations on sprouted seeds. National Advisory Committee on Microbiological Criteria for Foods. Int J Food Microbiol Nov 15;52(3):123-53.
Fahey JW, Haristoy X, Dolan PM, et al. (2002). Sulforaphane inhibits extracellular, intracellular, and antibiotic-resistant strains of Helicobacter pylori and prevents benzopyrene-induced stomach tumors. Proc Natl Acad Sci U S A May 28;99(11):7610-5.
Kim DJ, Shin DH, Ahn B, Kang JS, Nam KT, Park et al. (2003). Chemoprevention of colon cancer by Korean food plant components. Mutat Res Feb-Mar;523-524:99-107.
Thomas JL, Palumbo MS, Farrar JA, et al. (2003). Industry practices and compliance with U.S. Food and Drug Administration guidelines among California sprout firms. J Food Prot Jul;66(7):1253-9.