Rethink Food Safety Habits
Rethink Food-Safety Habits: E. coli,Salmonella Lurk in Items We Tend to Think of as Clean
June 14, 2000
The Montreal Gazette
Columnist Schwartz writes that with the flood of headlines on the effectsof E. coli contamination, many people are giving food-safety issues a littlemore thought.
Safepreparation of products such as meat and poultry might be standard practicein homes across the country, but there are other sources of food-borne illnessthat might surprise people. Considering the potential consequences, it may betime to take note.
Hereare five foods that warrant special attention:
Alfalfa andsimilar sprouts have been found to contain bacteria such as salmonella and E.coli, the same deadly strain linked to the water contamination in Walkerton,Ont. And because these types of sprouts are usually eaten raw, it’s recommendedthat they be avoided by people most susceptible to complications from thesebacteria – the old, young children and those with compromised immune systems.
If youare not in any of these groups and still want to eat them raw, Health Canadaoffers these suggestions: Buy only sprouts that appear crisp and have budsattached. Avoid those that are dark or musty smelling. Once you have them home,keep them refrigerated. And before eating, rinse sprouts thoroughly with water.Respect the best-before date. Which brings up the question: when eating out,what are the chances that all these recommendations have been adhered to?
While raw beansprouts are a popular salad item, it might be wise to limit their use tocooked dishes. The high temperatures of cooking will reduce the risk ofillness.
Washingcantaloupes might not be common practice, but it should be. There have beenreports of salmonella outbreaks as a result of eating cantaloupe cut fromunwashed rinds. The most recent occurred in the U.S., where residents ofseveral states, including California and Oregon, became ill. By washing the rindyou avoid contaminating the flesh when you cut into the melon. Best to handlecantaloupe in the same way as raw meat: wash your hands before and afterhandling.
Many people think that these mixes, because they require no trimming, have beenpre-washed. Not so. Rinse thoroughly with plenty of water to rid the lettuce ofany potential causes of food poisoning.
It’s been shown that washing lettuce leaf by leaf rather than in cut sectionsmakes for a safer salad.
High-Selenium Broccoli vs.Colon Cancer
Selenium. It’s an essential traceelement that helps keep the immune system humming and free radicals undercontrol. Recent evidence from human studies suggests that the mineral reducesthe incidence of cancer when taken in higher doses than most diets supply.
Thatnews has prompted increased use of selenium supplements. Sales rose from $60 to$66 million-a 10-percent increase-between 1996 and 1997, according to mostrecent statistics from the Nutrition Business Journal published in SanDiego, California.
Theidea of selenium supplements doesn’t sit too well with nutritionists like JohnW. Finley and Cindy D. Davis at the ARS Grand Forks Human NutritionResearch Center in North Dakota. They know the selenium salts in somesupplements can be toxic when too much is ingested. On the other hand,”it’s harder to get too much selenium through foods,” says Davis.
Differentfoods package selenium in different biochemical forms. And the body uses theseforms differently, explains Finley. An expert in selenium nutrition, he wants tofind what form or forms provide the widest range of health-promotingproperties-including cancer prevention.
Broccoli’sGot the Right Stuff
Recentresearch in Finley’s lab is demonstrating that high-selenium broccoli may be thebest source of an anticancer agent. Other researchers discovered that garlicstores selenium in a form that appears to be most active against cancer. Andbroccoli and brussels sprouts also store selenium in this form, known asselenium methyl selenocysteine, or SeMSC. The body simply snips the end off thisamino acid to produce the anticancer agent-methyl selenol.
Thoughgarlic is higher in SeMSC, most Americans are not likely to eat enough of it toproduce the desired effect, Finley notes. So his group has focused on testingselenium-enriched broccoli as a way to get effective levels of SeMSC into thebody.
Alongthe way, however, he learned how animals and people metabolize other food formsof the mineral. “It’s a long and tortuous path for the form of seleniumprevalent in grains and some meats-selenomethionine-to get converted tomethyl selenol. It’s easier for selenium salts-the forms used in somesupplements-to get there. And it’s only one step for the form inbroccoli,” Finley says.
In aseries of rat studies, Finley, Davis, and former colleague Yi Feng, now with theUniversity of Louisville’s medical school, confirmed that differences inselenium metabolism translated to differences in the risk of colon cancer.First, they demonstrated that selenium salts-both selenate and selenite-canprevent the first of several steps that can lead to cancer, whereas the grainform-selenomethionine-was ineffective.
Seleniumsalts reduced the number of adducts in the rats’ colons by 53 to 70 percent.Adducts are formed when a carcinogen binds to DNA, explains Davis. “If thedamage isn’t repaired, it can lead to tumor formation.”
Theresearchers had beefed up the rats’ selenium levels through their diets forseveral weeks. Then they injected the animals with a potent carcinogen calledDMABP, for short. Their findings support those of others showing that seleniteprotects against adduct formation in rats’ mammary cells.
Thegroup got similar results when they looked for a later stage of colon tumorformation called aberrant crypts. These are immature colon cells that have goneawry. “Not all aberrant crypts develop into cancer,” says Davis,”but all colon cancers begin as aberrant crypts.” Feng painstakinglycounted the crypts and found more in the animals fed selenomethionine than inthose getting selenium salts.
Beefed-UpBroccoli Works Best
Themost exciting phase of this work started in a Grand Forks greenhouse. Theresearchers grew ordinary broccoli in soilless media with added selenium toobserve uptake of the metal. Finley says that studies show that broccoli grownin the presence of selenium can accumulate substantial amounts. Some commercialbroccoli grown in California has up to 50 times more selenium than normal, henotes, because the irrigation water is naturally high in the mineral. WhenFinley analyzed his broccoli, however, he found it had 100 to 200 times moreselenium than the California heads.
Whenthe researchers pitted the high-selenium broccoli against the salt form selenatein rat studies, they made sure to control for any beneficial effects of broccoliitself. The vegetable is high in antioxidants and contains other substancesshown to be active against cancer. So animals in each test group got ordinarybroccoli as well as the treatment.
Treatmentsconsisted of daily doses of either 0.1 or 1.0 mg of selenium per kilogram of therats’ body weight, either in the form of enriched broccoli or selenate. Thehigher dose is representative of the selenium level that reduced cancer risk ina human trial, Finley says.
Aftergiving the animals DMABP, Feng again looked for precancerous aberrant crypts andfor collections of these cells, known as aberrant crypt foci. High-seleniumbroccoli always resulted in fewer precancerous lesions than selenate did, saysFinley-about one-third fewer at the 1.0 mg/kg dose. And the number of lesionsdecreased as the dose increased.
Theresults were so promising that Finley and Davis decided to repeat theexperiment. And they confirmed the findings using a different salt-seleniteinstead of selenate-and a single but higher dose of selenium-2.0 mg/kg. Theyalso gave the animals a much more potent carcinogen-dimethyl hydrazine (DMH).Although it produced many more lesions, the rats fed high-selenium broccoli hadhalf as many aberrant crypts as the animals getting selenite.
“Ifthere’s a call to increase selenium intake, we currently have few choices otherthan high-selenium yeast or selenium salts,” says Finley.”Selenium-enriched broccoli is a potential source of the mineral in ahighly effective form.” His group is looking for other potential benefitsof the enriched vegetable.-By Judy McBride, Agricultural Research ServiceInformation Staff.