The salad you just ate may not be as healthy as you thought. If sprouts were involved, you might have been exposed to deadly bacteria.
A study in this week's Annals of Internal Medicine found that more than half of confirmed food-borne illnesses in California were linked to alfalfa or clover sprouts between 1996 and 1998.
The study investigated six multi-county outbreaks of bacterial infection in California from 1996 through 1998. There were 600 confirmed cases of disease, and two deaths associated with eating sprouts. The study estimates that an additional 22,800 people were infected, but never realized that sprouts were the cause.
"Although sprouts are often touted as a health food, they are potentially hazardous and can cause significant morbidity and even death," wrote the study's lead author, Janet Mohle-Boetani of the Los Angeles County Department of Health Services. The department is part of the California Department of Health Services, which conducted the study with the federal Centers for Disease Control.
During the study period, sprouts caused more outbreaks than any other food, though the common perception is that undercooked meat, and eggs and contaminated water supplies are usually the culprits of the bacteria in question: E. coli and salmonella.
What Is Contaminating Sprouts?
The six outbreaks involved two types of bacteria: Escherichia coli 0157 and salmonella. These bacteria are often associated with animal waste, and are commonly the cause of many food-borne illnesses. Symptoms can include anything from upset stomach to severe dehydration and death.
The seeds from which sprouts are grown are often the source of the bacteria. The seeds can be contaminated by irrigation water, fertilizer containing animal manure, or by grazing livestock.
To grow sprouts, the seeds are put into a rotating drum and misted with warm water. They are left at room temperature to sprout, providing a perfect incubator to increase the population of bacteria that may be present.
Who Is at Risk?
The bacteria involved are capable of infecting anybody. Those at the highest risk include children, people with weak immune systems (including pregnant women), and the elderly. The symptoms that result from infection in these individuals can be much more severe because they are not as well equipped to fight off the bacteria.
The sprouts are most often eaten raw on salads and sandwiches, leaving the bacteria unharmed. The Food and Drug Administration suggests cooking the sprouts in order to kill any bacteria that might be present.
"In order to minimize risk for food-borne illness avoid raw sprouts," said a spokesperson for the FDA. Washing sprouts is not effective, because bacteria on the seed can become internalized during sprouting.
What Is Being Done?
Recently the FDA released a consumer advisory for sprouts. Guidelines were also put in place for decontamination of seeds. All growers are required to sanitize the seeds chemically before growing sprouts. The FDA has also approved irradiation for decontaminating seeds, but not for sprouts.
But the process does not eliminate the problem of possible contamination during the growing process. Although the disinfecting process is good, there is no way to eliminate all pathogens. In addition, if equipment used in the process is not properly disinfected, contamination can occur regardless of how "clean" the seeds are.
The study concludes: "Raw sprouts should not be served in facilities for high-risk persons, such as child care centers, preschools, kindergartens, assisted living facilities, nursing homes, long-term care facilities, and hospitals."