Can Good Bacteria Really Fight the Flu?

Study shows probiotics can ward off viral infections like the cold or flu.

ByABC News
July 24, 2009, 2:28 PM

July 27, 2009 — -- Cold and flu sufferers, there may be a way to head off those irritating symptoms before they cause you to miss work or school.

New evidence suggests that probiotics -- good bacteria that can aid immune function -- can have a preventive effect for cold and flu viruses.

In a study sponsored by Danisco, a Danish nutritional supplement company that makes probiotics products, researchers found that a six-month course of probiotics was a safe and effective way to ward off flu symptoms and reduce their duration in 3- to 5-year-olds.

"There was definitely a need to show a prophylactic benefit of probiotic consumption, especially in children," said Gregory Leyer, the former head of research and development at Danisco's Madison, Wis., offices and the author of the study, published today in the journal Pediatrics.

But infectious disease experts caution that there are several things to consider when looking at the study's results, chief among them being that the study was sponsored by a company that manufactures probiotic products as well as the study being conducted on children in China rather than in North America.

Nearly 250 kids were treated twice daily for six months. One group of children received a single strain of the probiotic called Lactobacillus acidophilus, one group received a combination of the L acidophilus and Bifidobacterium probiotics, and a third group received a placebo.

Compared to the placebo group, the single and combination probiotics had reduced fever incidence by 53 percent and 72.7 percent, respectively, decreased coughing by 41.4 percent and 62.1 percent, and reduced runny noses by 28.2 percent and 58.5 percent. The groups also used less antibiotics, and missed fewer days of school or childcare because of the flu.

"About 60 to 80 percent of our immune cells are associated with gut [cells]. Hitting the immune system through the gut makes sense," Leyer said. "I'm assuming that's how this product works. That kid's immune system is in a better state to fight off infections or reduce the symptoms quicker."

Previous studies on the effects of probiotics on immune health have been mixed, with some patients showing no response to probiotics and others showing little to moderate response.

"It is a surprising result and one that is hard to reconcile with traditional medical wisdom," said Dr. Julie Gerberding, former director of the federal Centers for Disease Control and Prevention in Atlanta. "I would take them as 'interesting but still very preliminary.'"

Dr. Kathi Kemper of Wake Forest University Baptist Medical Center in Winston-Salem, N.C., says there is still more to learn about dose, kind of bacteria and duration of probiotic treatment. "Most practitioners will feel more confident when these results are replicated in trials sponsored by government or other parties without a potential conflict of interest," she said.

Other doctors say the function of the bacteria in the body makes using probiotics for viral infections seem an intuitive choice, especially for those who wish to try a non-drug approach.