Beneficial bacteria called probiotics find their way into mainstream products.
How about having some bacteria with your breakfast cereal?
That's the idea behind the growing nutritional trend of eating food with probiotics -- "friendly" bacterial strains that may help thwart an array of conditions from allergies, asthma and eczema to gastrointestinal ailments.
Probiotics are believed to have virtually no side effects, and exploiting friendly microbes fits with the trend to promote health and treat conditions with fewer prescription medications.
So it should be no surprise to see that probiotics are turning up in breakfast cereals, yogurt, beverages and cheese. And they're not just relegated to the dusty corners of health food aisles. Kraft, Post, Dannon and Kashi are among the mainstream food companies now selling products fortified with probiotics. Dannon is using teen sensation Miley Cyrus of "Hannah Montana" to help market one of its yogurts containing probiotics --Danimals -- to kids.
Probiotics seem to work by changing the mix of bacteria that already colonize our bodies. In the gastrointestinal tract, having more healthy bacteria can help squeeze out unfriendly bacteria and viruses that cause harm. Probiotics have shown some potential in thwarting foodborne infections such as salmonella and E. coli. They seem to be effective in helping to treat rotavirus, which strikes infants and children, and they show promise against gastrointestinal infections that can hit the elderly in assisted-living and nursing homes. Probiotics appear to help ease irregularity, may reduce symptoms of irritable bowel syndrome and can prevent the diarrhea that often occurs with antibiotic use.
The friendly bacteria in probiotics also appear to help dampen overactive immune systems that result in allergies, asthma and other autoimmune conditions. A recent study in Finland showed that 2-year-olds with a family history of allergies who were given probiotics were less likely to develop eczema, a chronic itchy skin condition.
Probiotics could also boost overall health. In one recent German study, researchers found that regular consumption of probiotics cut the duration of the common cold by two days and lessened symptoms when colds occurred. In a few studies, healthy children and adults who took probiotics had fewer school and work absences than their counterparts who didn't take this friendly bacteria.
"It's really interesting," said microbiologist Mary Ellen Sanders, executive director of the International Scientific Association for Probiotics and Prebiotics (carbohydrates that help friendly bacteria thrive).
Even so, Sanders and others who study probiotics say that there still isn't enough positive evidence to support their widespread use.
"I would not want to offer any false hope," says R.A. Rastall, head of the food bioscience department at Britain's University of Reading. "We still need to do more work."
That's because scientists can't agree on an exact definition of probiotics. Some say that probiotics include any food, such as yogurt or kefir, with live cultures of friendly bacteria. But microbes in those products don't always survive transit through the acid-filled stomach. So other scientists say that a true probiotic must contain enough hearty cultures to survive and produce measurable health effects.
"There are a lot of products calling themselves probiotic foods, but we don't know if they have efficacious levels" of bacteria," said Sanders. It's difficult for consumers to know what to choose, she said, "because there's no stamp of approval where these things have been evaluated by independent third parties."
Still unknown are which strains of friendly bacteria are best to use for which purposes. There's little knowledge of optimal doses for effectiveness and uncertainty about the best way to deliver probiotics. Should they be given in dietary supplements -- the method used by many studies -- or added to food?
Even Sanders says she often struggles to determine which strains -- and amounts -- of probiotics are in various foods and other products.
So what does she do? She checks company websites for information. And if they don't provide what she's looking for, she calls the companies.
"It's very easy to say that all probiotics will work," Sanders says. "But they won't all work, and it is a detriment to the industry as a whole to say that there is this sort of generic approach that any product [with probiotics] will do anything."
But if you and your family enjoy eating the growing array of foods that contain live cultures, that's another story. "I would be perfectly happy to feed my kids probiotics," says the University of Reading's Rastall. "And I do eat them myself."
You can subscribe to the free Lean Plate Club e-mail newsletter at www.leanplateclub.com. Sally Squires is a writer for the Washington Post.