Sprouts may be small but pack a big foodborne illness punch

November 17, 2016

A new report is showing just how dangerous eating raw sprouts can be. Over the past two decades, researchers found various kinds of sprouts were responsible for sickening more than 2,500 people, sending 186 to the hospital and causing three deaths.

"Sprout contamination continues to pose a serious public health concern," the researchers from the Food and Drug Administration (FDA) wrote in their report. The arm of the FDA that wrote the new report focuses on investigating outbreaks and finding ways to prevent them.

From 1996 to August 2016, 48 outbreaks of illness were associated with sprouts, the researchers found, with alfalfa sprouts being the most common culprit with 30 outbreaks. In addition, there were seven outbreaks linked to clover sprouts, six outbreaks linked to mung bean sprouts, two outbreaks linked to unspecified sprouts, two outbreaks linked to multiple sprout types and one outbreak linked to a food ingredient called sprouted chia powder.

The researchers also found not one, but multiple times of bacteria responsible in the sprout outbreaks. Salmonella was implicated in the greatest number of outbreaks, at 35, followed by Escherichia coli (11 outbreaks) and Listeria monocytogenes (two outbreaks). Of the three sprout-related deaths during the study period, two were attributed to Salmonella and one to Listeria.

Sprouts "certainly rank up there" among types of produce that have been linked to outbreaks, said Dr. Kathleen Gensheimer, the director of the FDA's Coordinated Outbreak Response and Evaluation Network and the lead author of the study. This, she explains, is because of the way sprouts are grown.

To grow sprouts, seeds are placed in water in a warm, humid environment that is ideal for rapid bacterial growth. That means if a seed is contaminated with bacteria before the sprouts are grown, the problem gets worse during the sprouting process, because the bacteria will multiply, Gensheimer explained. In most sprout outbreaks, the outbreak stemmed from seeds that had been contaminated with bacteria before the sprouting process began, she continued. Bacteria can get on a seed when it's being harvested and can survive for months in the dry conditions in which the seeds are stored.

Alfalfa sprouts, the most common source of an outbreak in the study, are the most popular type of green seed sprouts that are typically eaten raw, Gensheimer said. Sprouts that come from green seeds, including alfalfa sprouts, clover sprouts and radish sprouts, typically aren't cooked before they are eaten, and so they are more commonly associated with outbreaks. In contrast, sprouts that come from beans, such as mung bean sprouts and soy bean sprouts, typically are cooked.

Gensheimer explained thoroughly cooking sprouts can reduce a person's risk of getting sick, because cooking can kill the harmful bacteria, but said they are also a "stealth ingredient” — often added to sandwiches or a salads in a restaurant or deli without being mentioned.

Currently, the U.S. government says that people who are the most at-risk for infectious diseases should avoid eating raw or lightly cooked sprouts of any kind. This includes children, the elderly, pregnant women and people with weakened immune systems.

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Category: Food Safety