Questions Keep Sprouting About Sprouts
New Sprout Warnings Issued July 9, 1999.
US FDA
by Paula Kurtzweil
Sprouts--those crunchy, healthy newborn
plants often associated with the hippie days of the 1960s--have in this decade
become regulars in salad bars and produce departments across the country. But
along with their increasing presence has come an increasing frequency of
sprout-related food-borne illness.
The federal government has linked the most
common kind--alfalfa sprouts--to a number of food-borne disease outbreaks, most
occurring since 1995. The disease culprits included the bacteria Salmonella and
Escherichia coli O157:H7, a particularly dangerous pathogen.
These outbreaks led the Food and Drug
Administration in August 1998 to issue a health advisory for high-risk groups
warning them not to eat raw alfalfa sprouts and, in September, to conduct a
public hearing to determine what further steps, if any, are needed to ensure the
safety of sprouts.
"There are some interesting questions
raised about sprouts," says Karen Hulebak, a science policy analyst in FDA's
Office of Policy. "What do we know about the source of sprout contamination?
What should consumers do? ... There are a lot of uncertainties."
What Are Sprouts?
Sprouts, which are the germinating form of
seeds and beans, are easy to produce. They require no soil, only water and cool
temperatures. They emerge in two to seven days, depending on the type of seed or
bean. In addition to raw alfalfa sprouts, other varieties include clover,
sunflower, broccoli, mustard, radish, garlic, dill, and pumpkin, as well as
various beans, such as mung, kidney, pinto, navy and soy, and wheat berries.
Many are sold individually, some in mixtures.
Potomac Glen Farms in Potomac, Md., sells
a wide array. Each offers a distinct flavor, suggesting, as sprout growers like
to point out, that sprouts indeed work well in a variety of dishes, such as
soups, salads, sandwiches, and stir fries. Nancy Snider, owner of Potomac Glen
Farms and president of the International Sprout Growers Association, says one of
her favorite foods is sprouts with peanut butter and crackers.
While versatile, sprouts also are favored for their nutritional value. Like
other fresh produce, sprouts are low in calories and fat and provide substantial
amounts of key nutrients, such as vitamin C, folate and fiber (see
text alternate for chart).
A 1997 Johns Hopkins University study suggested raw broccoli sprouts may be
particularly rich in sulforaphane, a compound that may mobilize the body's
natural cancer-fighting resources and reduce the risk of developing cancer.
Though popular in this country in only the
past few decades, sprouts have actually been around for thousands of years. Mung
beans have been used in Chinese foods for years--though usually in cooked
dishes.
Today, sprouts in the United States are a
$250-million market. Some 475 U.S. sprout growers produce 300,000 tons of
sprouts every year, according to the International Sprout Growers Association.
As many as 10 percent of Americans eat sprouts regularly.
Food-Borne Illnesses
Sprouts have only recently emerged as a
recognized source of food-borne illness. Since 1995, health officials have
attributed 13 food-borne disease outbreaks worldwide to sprouts. Ten of these
outbreaks occurred in the United States, resulting in illnesses in at least 956
Americans and at least one death.
Four of the outbreaks were caused by E.
coli bacteria, and three of those involved the most dangerous strain, E. coli
O157:H7. The biggest outbreak occurred in Japan in 1996; 9,000 people were
sickened and 17 died after eating radish sprouts contaminated with E. coli
O157:H7. (Note from ISS: The High Court of Japan has since
determined that radish sprouts were not involved in this outbreak;
See:
"High Court Orders Gov't to Redress
Radish Sprout Growers", May 21/03, Kyodo.)
The O157:H7 strain produces toxin in the
human gut that damages cells of the intestinal lining. This allows blood to pass
into the stool. Other symptoms of O157:H7 infection are stomachache, nausea and
vomiting. Infection can lead to hemolytic uremic syndrome (HUS), a major cause
of acute kidney failure in children in this country. HUS is fatal in about 3 to
5 percent of cases.
Many of the outbreaks have involved raw
alfalfa sprouts or mixed sprouts containing raw alfalfa sprouts contaminated
with Salmonella.
In people, Salmonella can cause
salmonellosis, an illness characterized by fever, stomach cramps, and diarrhea.
The illness can last as long as seven days, and severe cases may require
hospitalization. In some people, it can cause death. A small number of illnesses
may develop into recurring joint pain and arthritis.
Where do these bacteria come from? It's
believed that the seeds from which sprouts are derived are often the source.
Some of the seeds may become contaminated by animals in the field or during
post-harvest storage, for example. Also, the use of animal manure in fields of
alfalfa intended for nonhuman use may be a problem if seed is used for
sprouting.
The ideal conditions provided by
germinating seeds and beans--namely abundant nutrients in this phase of plant
growth, high levels of moisture needed to produce sprouts, and heat generated
from the sprouting process--help ensure the survival and growth of bacteria. "In
the sprouting environment, bacteria can grow quickly," says Robert Wick, Ph.D.,
a plant pathologist with the University of Massachusetts and one of the
presenters at FDA's September 1998 public hearing on sprouts.
So far, mishandling of sprouts during
production, packing or distribution has not been implicated as the source of
sprout contamination. However, bacteria already present in the sprouting seed
can continue to thrive in conditions in which poor food handling techniques are
practiced--for example, lack of refrigeration, infected workers, and dirty and
unsanitary sprouting facilities.
Preventive Measures
Following three 1998 food-borne disease
outbreaks involving raw alfalfa sprouts, FDA in August reaffirmed a warning that
had been issued by the national Centers for Disease Control and Prevention in
1997. The advisory urged people at high risk for severe food-borne
disease--children, the elderly, and people with compromised immune systems--to
avoid raw alfalfa sprouts until methods to improve the safety of sprouts can be
identified and put in place.
In September, the agency held a two-day
public meeting on sprout safety to learn, among other things, possible
preventive measures to ensure safe sprouts. Representatives from the sprout
industry and consumer groups, as well as scientists and regulators, presented
information to the Fresh Produce Subcommittee of the National Advisory Committee
on Microbiological Criteria for Food.
High on the list of possible strategies
was decontamination of sprout seeds. The most promising method is chemical
treatment with calcium hypochlorite. It already is in use in California on an
emergency basis, as approved by the state's environmental protection agency. FDA
is working with the U.S. Department of Agriculture to get the treatment approved
by the U.S. Environmental Protection Agency, which oversees use of chemicals on
raw agricultural products, such as sprout seeds.
Irradiation, in which a measured dose of
ionizing radiation is applied to a food product, appears to work well in
decontaminating sprout seeds, especially when used in conjunction with calcium
hypochlorite. Irradiation of sprout seeds would require FDA approval. (See "Irradiation:
A Safe Measure for Safer Food" in the May-June
1998 FDA Consumer.)
Heat treatment (the same as
pasteurization) has limited appeal because there is such a fine threshold at
which bacteria can be killed and germination not destroyed.
Other preventive measures would focus on
production and distribution of sprouts. Possibilities include mandatory Hazard
Analysis and Critical Control Point (HACCP) programs for sprout growers. HACCP
focuses on identifying and preventing hazards, such as bacterial contamination,
rather than relying on spot-checks of production processes and random sampling
of finished products. Emphasis on good agricultural and manufacturing practices
of sprouts also may help reduce the incidence of sprout-related food-borne
disease outbreaks. Another option might be to include a list of safe handling
practices or a mandatory warning on labels of sprout packages. The warning would
echo FDA and CDC recommendations for high-risk groups.
According to LeAnne Jackson, Ph.D., a
science policy analyst in FDA's Center for Food Safety and Applied Nutrition,
the National Advisory Committee on Microbiological Criteria for Food was
awaiting the subcommittee's recommendations at press time. If endorsed, the
recommendations will be forwarded to FDA for consideration.
In the meantime, the International Sprout
Growers Association planned to begin in November 1998 a voluntary quality
assurance program in which sprout growers agree to follow ISGA-established
sanitation guidelines based on good manufacturing practices. According to ISGA
president Snider, sprout growers that participate could label their products as
ISGA-certified as long as their facilities pass inspection by a third-party
auditor.
The sprout industry also is working with
the National Center for Food Safety and Technology--a consortium of government,
industry and academia devoted to food safety research--in Summit-Argo, Ill., to
study sprout safety. The center is conducting a six-month research project to
verify the effects of chemical, heat and irradiation treatment of seeds on
sprout safety.
Snider says the industry is involved
because it wants to reduce any hazards associated with sprouts. "This is a
difficult time for us," she acknowledges. "But out of difficulties, something
good can come. We expect [these concerns over sprout safety] to turn out to be
our best friend. We want our products to carry zero risk."
Paula Kurtzweil is a member of FDA's
public affairs staff.
How to Eat Sprouts Safely
If you belong to one of the groups at high
risk for food-borne disease--children, the elderly, and people with compromised
immune systems--avoid raw alfalfa sprouts.
If you are a healthy adult, follow these
tips:
-
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. The
refrigerator should be set at no higher than 40 degrees Fahrenheit (4 degrees
Celsius).
-
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. Do not use soap or other
detergents.
--P.K.
Nutritional Value of a Cup of
Raw Sprouts
Alfalfa
-
calories--10
-
protein--1.3 grams
-
fiber--3 %DV
-
vitamin C--5 %DV
-
iron--2 %DV
-
folate--3 %DV
Mung Bean
-
calories--26
-
protein--2.5 grams
-
fiber--4 %DV
-
vitamin C--23 %DV
-
iron--4 %DV
-
folate--9 %DV
Radish
-
calories--16
-
protein--1.4 grams
-
fiber--n/a
-
vitamin C--18 %DV
-
iron--2 %DV
-
folate--9 %DV
Soybean
-
calories--86
-
protein--1.3 grams
-
fiber--3 %DV
-
vitamin C--5 %DV
-
iron--2 %DV
-
folate--3 %DV
Wheat
-
calories--214
-
protein--8.0 grams
-
fiber--4 %DV
-
vitamin C--5 %DV
-
iron--11 %DV
-
folate--10 %DV
(Source: U.S. Department of Agriculture)
FDA Consumer magazine
(January-February 1999)
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