While more than 3.9 million Americans have consumed some form of probiotics, there is not enough evidence to support their use for most digestive conditions, according to clinical guidelines released by the American Gastroenterological Association (AGA). The guidelines, published in Gastroenterology, focus on probiotics across multiple GI disorders while also examining the effect of each single-strain or multi-strain formulation on their own rather than grouping them all under one probiotic “umbrella.”

Using certain probiotic formulations in three settings is supported by the AGA guidelines: preventing necrotizing enterocolitis in low birthweight preterm babies, managing a complication of inflammatory bowel disease called pouchitis, and preventing Clostridioides difficile (C. difficile) in adults and children who are on antibiotics.  

For adults and children on antibiotic treatment, the AGA guidelines suggest using S. boulardii; or the two-strain combination of L. acidophilus CL1285 and Lactobacillus casei LBC80R; or the three-strain combination of L. acidophilus, Lactobacillus delbrueckii subsp. bulgaricus, and Bifidobacterium bifidum, or the four-strain combination of L. acidophilus, L. delbrueckii subsp. bulgaricus, B. bifidum, and Streptococcus salivarius subsp. thermophilus over no or other probiotics for prevention of C. difficile infection.

There wasn’t enough evidence to recommend taking probiotics to treat Crohn’s disease, ulcerative colitis, irritable bowel syndrome (IBS), and C. difficile infection, the guidelines say, and the AGA recommends not using probiotics to treat acute infectious gastroenteritis in children.

“One downside to taking probiotics is the cost,” Grace L. Su, MD, of the University of Michigan, said. “There just isn’t enough evidence in many cases to prove a benefit. And in some cases, there is a potential downside. For example, if you give someone a live organism like probiotics and their immune system is compromised, the probiotics could go into the bloodstream and cause an infection.”

Dr. Su recommends that gastroenterologists suggest probiotics to their patients only when there is a clear benefit. She said it also is important for them to be aware that the effects of probiotics are not species-specific but strain-and combination-specific. “We were very vigorous in our review, and we paid a lot of attention to the different strains that could be helpful in different situations,” she said. “Just as you wouldn’t recommend to a patient that they go take any antibiotic, you wouldn’t just recommend going on any probiotic. Like antibiotics, probiotics are not all the same.” 

She recommended telling patients who currently take probiotics for Crohn’s, ulcerative colitis, or IBS to consider stopping. “There is not enough evidence to confirm a lack of harm,” she said.

The ADA guidelines recommend specific probiotics for preterm (born before 37 weeks) and low birth weight infants because these could prevent mortality and necrotizing enterocolitis, decrease the length of a hospital stay, and decrease the number of days needed to reach full feed.

While probiotics are believed to be safe for healthy people, the long-term consequences are 

unknown, the AGA says, and the potential harm and benefit must be considered. In addition, the FDA has not approved any probiotic product to treat a medical condition.