I really miss topping my salads off with a handful of alfalfa sprouts. What makes them so unsafe?

It doesn't seem that long ago that sprouts were ubiquitous at every salad bar you approached. Not so much anymore. They've even disappeared from some major grocery store chains after numerous outbreaks traced to sprouts in recent years.

The problem is in the way sprouts grow: Seeds need warm, moist growing conditions to sprout - exactly the conditions that illness-causing bacteria, such as Salmonella and E. coli, need to thrive.

Even if there's just a small amount of bacteria on or inside a seed, those cells can multiply to dangerous levels within hours in such conditions.

The irony is that raw sprouts have long been touted as one of nature's most potent health foods. But as their popularity grew in the 1980s and 1990s, so did the reported number of illnesses associated with them.

According to the Food and Drug Administration, there were 34 outbreaks associated with sprouts between 1996 and 2010 - the most associated with any type of produce. In fact, sprouts were responsible for more than one-quarter of all produce-related outbreaks - more than those from melons, tomatoes or leafy greens.

The problem isn't confined to the U.S. In 2011, nearly 4,000 people in Europe, primarily in Germany, became ill and 53 died from eating bean sprouts from a German organic farm contaminated with a rare strain of E. coli. Some of those people actually grew their own sprouts from seed - seed that originated from the implicated farm.

Although growers can take steps to reduce the risk from bacteria growing in sprouts, no method can absolutely be determined safe. Thorough cooking kills the dangerous bacteria, but few people cook raw sprouts.

The FDA says people most at risk from foodborne illness - children, the elderly, pregnant women and anyone with a weakened immune system - should avoid eating raw sprouts of any kind, including alfalfa, clover, radish and mung bean sprouts.

If you decide to eat raw sprouts anyway, the FDA offers these tips to reduce your risk:

• Buy only sprouts kept at refrigerator temperature. Select crisp-looking sprouts with the buds attached. Avoid musty-smelling, dark or slimy-looking sprouts.
• Refrigerate sprouts at home. Refrigerators should be set to maintain a temperature of 40 degrees F or below.
• Wash hands with warm water and soap for at least 20 seconds before and after handling raw foods.
• Rinse sprouts thoroughly with water before use. Rinsing can help remove surface dirt. Don't use soap or other detergents.

Chow Line is a service of Ohio State University Extension and the Ohio Agricultural Research and Development Center. Send questions to Chow Line, c/o Martha Filipic, 2021 Coffey Road, Columbus, OH, 43210-1044, or filipic.3@osu.edu.