'Good' Bacteria: Good for Colds?

Researchers Say Workers Who Took Probiotics Reported Fewer Sick Days

Medically Reviewed by Louise Chang, MD on November 07, 2005

Nov. 7, 2005 - "Eat your bacteria," is not something you hear every day, but it could prove to be good advice for people who want to stay healthy.

During the past few years, interest in the health benefits of probiotics or so-called "good" bacteria has grown. Found in certain yogurts and in supplement form, probiotics are increasingly used to treat diarrhea and other gastrointestinal ailments.

Now a new study suggests that they may also help prevent respiratory infections like the common cold.

Researchers in Sweden compared workers who took the probiotic bacteria Lactobacillus reuteri every day with those who didn't. The workers who took the probiotic had less than half the sick leave of workers who didn't.

The study was paid for by BioGaia AB, the Swedish biotechnology company that markets a line of L. reuteri products.

Good Bugs

There are more than 400 species of bacteria in the human digestive tract, and it is commonly believed that at least some of these help prevent illness by keeping sickness-causing bacteria from flourishing.

The "good bug" theory has been bolstered by research showing that the immune systems of animals brought up in completely germ-free environments do not fully develop, and that such a protected environment promotes, rather than prevents, illness.

The newly published study from Sweden included 181 factory workers who consumed a drink containing L. reuteri or a drink without the probiotic for 80 days.

Twenty-three of the 87 workers in the placebo group reported taking sick days during the study, compared with only 10 of the 94 workers who took the L. reuteri.

The difference was most dramatic among 53 shift workers: none of the 26 shift workers in the L. reuteri group reported taking any sick leave, compared with nine out of 27 shift workers in the placebo group.

Buyer Beware

The study is not the first to suggest that probiotics help protect against respiratory, as well as gastrointestinal disease. In a 2001 study, children who drank milk containing the probiotic Lactobacillus GG were found to have fewer respiratory infections than children who didn't.

But the researcher who discovered Lactobacillus GG tells WebMD that while it is clear that probiotics are beneficial for the treatment of certain types of diarrhea, questions remain about other health benefits.

In the 1970s a leading yogurt company ran ads suggesting that people who eat yogurt live longer. Tufts University professor of community health Sherwood Gorbach, MD, says the claim has not been proven in the decades since.

Certain raw or unpasteurized yogurts have enough of the right kind of bacteria to be considered probiotics, but most commercially available yogurts do not.

There has been an explosion of probiotic supplements in recent years. Since probiotics are not regulated by the FDA, figuring out which ones are potentially beneficial instead of a waste of money is a daunting task, says Gregor Reid, PhD, who directs the Canadian Research and Development Center for Probiotics in London, Canada.

Reid says L. reuteri and L. GG are among the most well-tested strains.

"The bottom line is that there are probiotics that are proven clinically and do benefit people," he says. "This is an incredibly exciting field, and there is certainly the potential to develop disease-specific probiotics in the future."

Show Sources

SOURCES: Tubelius, P., Environmental Health, 2005; vol 4: online edition. Py Tubelius, MD, occupational health specialist, Tetra Pak Occupational Health and Safety AB, Lund, Sweden. Sherwood Gorbach, MD, professor of community health and medicine, Tufts University, Boston. Hatakka, K, British Medical Journal, 2001; vol 322. WebMD Feature: "The Good Bugs." Gregor Reid, PhD, University of Western Ontario; director, Canadian Research and Development Center for Probiotics, London, Canada.
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