WASHINGTON (XINHUA) - Researchers studying the human digestive tract have found that probiotics have questionable benefits to gut health and may even delay the gut's natural ability to return to normal.
Probiotics are bacteria found naturally in food like yogurt and pickles, and are widely believed to contribute to one's gut health and help protect against certain ailments.
It is common for doctors to recommend taking probiotics during a course of antibiotic treatment which wipes out both good and bad bacteria in one's gut.
The two studies, published last Thursday (Sept 6) in the journal Cell, looked at how well probiotics colonise a healthy gut and how soon they help one's gut recover after antibiotic treatment.
Contrary to the common belief of probiotics' universal benefits, researchers discovered in the first study that the colonisation pattern of probiotics varies from one person to another.
"Some people accept probiotics in their gut, while others just pass them from one end to the other," said Dr Eran Elinav, an author of both studies and a professor in the Immunology Department at the Weizmann Institute of Science in Israel.
The difference is determined by a person's underlying microbiome composition and the immune system, the study said.
It tells us that the concept that everyone can benefit from probiotic supplements bought from a supermarket is empirically wrong, Dr Elinav was quoted by New Scientist magazine as saying.
Furthermore, researchers found that probiotics actually delayed the return of a person's normal microbiome to its original situation after antibiotic treatment rather than facilitating the process.
Participants in the second study were split into three groups. The first group were left to recover without any interventions, the second group was given probiotics, and the third was given their own gut bacteria collected before antibiotic treatment.
The researchers found that it took months for gut microbiome to return to normal in the second group while only a few days in the third group.
"Contrary to the current dogma that probiotics are harmless and benefit everyone, these results reveal a new potential adverse side effect of probiotic use with antibiotics that might even bring long-term consequences," Dr Elinav was quoted by Forbes as saying.
"This tells us that rather than relying on the one-size-fits-all approach, we need to move to a new paradigm: well-adjusted personal microbiome or signature combinations, tailored to the individual," he added.