NPR reports that for something many deem a “health food,” sprouts regularly appear on official outbreak lists. Since 1998 there have been at least 49 foodborne outbreaks, including 24 multi-state outbreaks and 1,737 illnesses tied to sprouts, according to a tally kept by Colorado State University.

Sandwich chain Jimmy John’s experienced multiple outbreaks linked to sprouts in 2008, 2009, 2010 and 2012. Sprouts are still on the menu, but place your order online, and a less than appetizing warning pops up: “The consumption of raw sprouts may result in an increased risk of foodborne illness and poses a health risk to everyone. Click ‘Yes’ if you understand the potential risks, or ‘Cancel’ if you’d like to continue without adding sprouts.”

Jimmy John’s may feel comfortable behind their warning label, but offering sprouts is a risk that Kroger and Wal-Mart no longer take — both grocery retailers have deemed sprouts too dangerous to sell. In announcing its decision in 2012, Kroger said it was based on a “thorough, science-based” review.

Sprout seeds need warmth and humidity to grow — which also happen to be ideal conditions for pathogens to flourish. Because of the number of outbreaks associated with sprouts, the FDA developed special requirements for sprout growers within the Food Modernization and Safety Act that is just going into effect. A few years ago, the agency also helped launch the Sprout Safety Alliance, with the Institute for Food Safety and Health at the Illinois Institute of Technology.

Linda Harris, a microbiologist at University of California, Davis, says sprouts continue to be a problem because they’re challenging. Whether they’re alfalfa, mung bean, red clover or radish sprouts, they’re grown in warm environments and usually eaten raw.

“Efforts to reduce risk include testing seed, testing seed water. Soaking seed in sanitizers is another — none of which are foolproof,” says Harris. “It reduces risk, but the fact is, we still see outbreaks on a regular basis.”

Continued outbreaks are one reason lawyer Bill Marler has been crusading for a warning label similar to the one adopted by Jimmy John’s. At least, until a magic bullet emerges to fix the problem. Harris says that hasn’t happened yet.

“I think there’s been an effort to find some solution, but honestly, as a microbiologist, I think [sprouts are] always going to be a higher-risk product, at least under current technology,” says Harris.