Probiotics help bloating and IBS

Across more than 80 placebo-controlled trials in adults with irritable bowel syndrome (IBS), some probiotic strains and combinations came out ahead of placebo on overall symptoms and abdominal pain. Confidence in those results is rated low to very low, and the results come from particular strains and combinations, not from probiotics as a category.

Within IBS, the pooled evidence for bloating relief is rated very low certainty, and a 2026 analysis found no difference from placebo on the bloating item of the standard IBS symptom score across 14 trials. In adults with bloating recruited from the general public, the two largest trials disagree. In 302 adults taking Bifidobacterium infantis 35624 for four weeks, symptom severity improved about as much on placebo as on the probiotic, though the probiotic group reported more bloating-free days. In 350 adults taking a 24-strain product combined with pomegranate extract for six weeks, bloating and gas scores were lower than on placebo; the trial was run online, and week-six data were available for 219 of the 350. Each trial was paid for by the company that sells the product tested.

The largest pooled analysis, 82 trials and 10,332 adults, rated the evidence strain by strain. Escherichia strains had moderate certainty of benefit for overall symptoms. Lactobacillus strains, including L. plantarum 299V, had low certainty for overall symptoms. Saccharomyces cerevisiae I-3856 and Bifidobacterium strains had low certainty for pain. Combination products and Bacillus strains had very low certainty for bloating. Only 24 of the 82 trials were judged at low risk of bias.

A 2026 analysis that searched to December 2025 included 40 trials. The 26 that reported the IBS Symptom Severity Score, with 4,098 participants, showed an average reduction of about 33 points more than placebo; the analysis treats 50 points as the smallest change that matters to patients. IBS-specific quality of life did not change significantly. Its trial sequential analysis concluded that the trials so far do not add up to enough data for a firm answer in either direction. Its abstract describes certainty as low and its full evidence table rates it very low, mainly because trial results disagree with each other.

Smaller trials report split results within the same study. In one, 60 adults with functional bowel disorders took Lactobacillus acidophilus NCFM with Bifidobacterium lactis Bi-07 for eight weeks. Overall symptom relief and treatment satisfaction, the trial's main measures, did not differ from placebo, while bloating scores improved more on the probiotic. That trial was registered after it ended, and the maker of the strains helped fund it.

On safety, adverse events were not more common with probiotics than with placebo across 55 trials and more than 7,000 participants. A 2011 US government evidence report on probiotic safety found the same in trials, but concluded that adverse events are poorly reported in probiotic studies and rare harms are hard to assess, so the research cannot yet answer safety questions with confidence. Case reports summarized by the NIH Office of Dietary Supplements describe bloodstream bacterial and fungal infections linked to probiotics, including at least 60 reports involving Saccharomyces cerevisiae products, mostly in people who were severely ill or immunocompromised.

Guidelines differ. The 2021 guideline of the American College of Gastroenterology suggests against probiotics for overall IBS symptoms, a conditional recommendation on evidence it rates very low, and notes that in the pooled analysis it drew on no category of probiotic reduced bloating. UK national guidance neither recommends probiotics nor advises against them. These trials were run in adults. Celiac disease and inflammatory bowel disease can cause symptoms that overlap with IBS with diarrhea. The trials enrolled adults with diagnosed IBS or, in two cases, adults from the general public with regular bloating.