(USA TODAY) -- Probiotics -- or live microorganisms intended to boost health, such as the bacteria in some yogurts -- have become popular items in vitamin stores and even many supermarkets. One of probiotics' most popular uses is in preventing and treating digestive problems.

A new analysis of 82 earlier studies finds that probiotics have potential in alleviating the diarrhea that afflicts about one-third of people treated with antibiotic medications. Probiotics reduced the risk of antibiotic-associated diarrhea by 42%, according to the analysis in today's Journal of the American Medical Association. Diarrhea is more common with certain antibiotics, particularly at high doses needed to treat serious infections.

Probiotics are sold as supplements at vitamin stores and supermarkets. Other foods, such as yogurts with active bacterial cultures, also market themselves as probiotics.

But the new study provides little specific guidance to patients or their doctors, says study co-author Sydne Newberry, a nutritionist and researcher for the Southern California Evidence-Based Practice Center at the RAND Corp. in Santa Monica.

The studies she reviewed didn't provide enough details -- such as the specific strain of bacteria -- for consumers to know exactly what to take and how often, Newberry says. Scientists need to conduct much more targeted clinical trials, testing particular doses of individual probiotics against one another, to give patients and their doctors better guidance, she says.

But the study underscores the importance of maintaining a proper balance of microbes in the digestive tract, says Roshini Rajapaksa, a gastroenterologist at the NYU Langone Medical Center who wasn't involved in the study. When people take antibiotics, the drugs kill not only the bad bacteria that cause illness but also the good microbes that help regulate the intestines, she says.

In the meantime, people should be careful about what they buy, especially when considering probiotics for children, says David Bernstein, chief of hepatology at North Shore University Hospital in Manhasset, N.Y.

Though foods such as yogurts are safe, probiotics could pose risks for children with weak immune systems, those who are chronically debilitated or those who are seriously ill, the American Academy of Pediatrics says. In rare cases, probiotics are associated with dangerous bloodstream infections.

Dietary supplements such as probiotics are not approved by the government for safety and effectiveness before they are marketed, the Food and Drug Administration says.

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