In the 1970s, Dannon ran an ad that featured ancient yet appealing Russian villagers—robust men with full white beards, strong and sturdy women who had aged with grace and dignity. Their secret, of course, was eating lots of yogurt. While I don’t think my daily yogurt will have me doing Russian dances on tables, a new study suggests that it may prevent the development of a real problem for many people—diarrhea caused by taking antibiotics.

In addition to killing bacteria that cause disease, antibiotics also kill bacteria in our intestines that help keep our guts healthy. These beneficial bacteria crowd out the less friendly strains that can cause problems like diarrhea. One of the worst of these is Clostridium difficile, a major scourge in hospitals, where it’s estimated that between 5 and 25 percent of people who receive antibiotics develop diarrhea. About 20 percent of those cases are caused by C. difficile, and the cost of treating one case of C. difficile diarrhea is estimated to be about $3,700.

Many dietitians—and, recently, some doctors—think that one way to fix this problem is by eating probiotics, or good bacteria, which helps to reset the natural balance in the intestines and thereby prevent a run on toilet paper. Yogurt contains active cultures that are thought to be probiotics, but we still have only a basic understanding of which bacteria actually are probiotics and exactly what they do.

In a recent study in the British Medical Journal, investigators divided up patients receiving antibiotics into two groups. One group received a commercially available probiotic yogurt drink called Actimel. The other group got a similar-tasting but sterile placebo. Only 12 percent of the patients who received Actimel developed diarrhea compared with 34 percent of the patients who got the placebo. None of the Actimel patients developed the more dangerous C. difficile diarrhea, compared with 17 percent of the placebo group. When you consider that the cost of treating a patient with Actimel was about $100, this seems like a pretty good deal.

As studies go, this one was well done. The investigators corrected for many factors that might have skewed their data, such as what antibiotics patients received, how long they took them, and what kind of infections they had. The researchers also did their statistical analysis using a rigorous standard called intention to treat, in which the results from all subjects involved in the study are counted, even if they fail to follow directions. The number of patients in the trial was relatively small (135), and we have no way of knowing which of the three bacteria in Actimel was responsible for the benefit, but these are small quibbles with a potentially important study.

Now, claims of the remarkable healing powers of dietary supplements generally raise an eyebrow or two among evidence-based, textbook-toting physicians who are all about the science of medicine. (I might even be labeled as one of those stodgy eyebrow raisers.) But when there is evidence to back up the claim, medicine does tend to embrace unusual treatments, and antibiotic-related diarrhea is a big problem just waiting for an effective remedy. There’s obviously still a lot we don’t know about probiotics, but this study provides us with the kind of credible information that could inspire doctors to prescribe little white tubs instead of little white pills.

Robert W. Lash, M.D. is an associate professor of internal medicine at the University of Michigan Medical School. His clinical interests include thyroid disease, diabetes, endocrine disorders in pregnancy, osteoporosis and metabolic bone disease, and medical education. A member of the LLuminari team of experts, a board certified internist and endocrinologist, Dr. Lash has an active clinical practice and is a hospitalist at the University of Michigan.