One of the most, well-studied benefits of probiotics is the prevention of diarrhea in people taking antibiotics (a condition known as antibiotic-associated diarrhea, or AAD). A recent meta-analysis of 82 randomized controlled trials published in the Journal of the American Medical Association evaluated the effects of probiotics on AAD and found that probiotics use is associated with a 42 percent lower risk of AAD.

Antibiotic-associated diarrhea occurs in up to 30 percent of people taking antibiotics and can result in early termination of antibiotic therapy in people wanting to avoid the uncomfortable side effect. You have certainly heard that antibiotics should be taken until the prescription is finished, however; this is because antibiotics continue to kill microbes even after you feel better.

Antibiotics are one of the most important medications ever created, no doubt. But they are also widely overprescribed. Antibiotics kill both harmful and beneficial bacteria. When the beneficial bacteria are killed, potentially pathogenic bacteria can gain the upper hand. The result: diarrhea. One particular pathogen—C. difficile—especially wreaks havoc on the digestive tract. Clostridium difficile-associated diarrhea is one type of AAD you don’t want. Dr. Smith and I have blogged on it before.

The meta-analysis builds on many previous studies, reviews, and even meta-analyses. Due to the high number of new studies added in the past five years, this most recent analysis only strengthens the evidence. The studies included the probiotics Lactobacillus, Bifidobacterium, Saccharomyces, Streptococcus, Enterococcus, and Bacillus. Although the researchers stated that more research is needed to determine which strains are most beneficial, they stated, “this analysis found no evidence that the effectiveness varies systematically even by probiotic genus.”

Next time you are prescribed antibiotics, ask your doctor about taking a probiotic along with it.