What Does the Research Actually Say About Probiotics and Bloating?

Bloating relief is the single most common marketing hook for probiotic supplements, and it’s worth applying this project’s own strain-specificity standard (see the companion “Probiotics 101” article) directly to it: what does the actual trial evidence say, for the actual strains being sold for this actual symptom? The honest answer, once the two most directly relevant trials are read rather than summarized, is more sobering than the marketing suggests.

The short version

• The most heavily marketed bloating-specific probiotic strain, Bifidobacterium infantis 35624, has now been tested in two dedicated randomized, placebo-controlled trials — and neither found it beat placebo on its primary bloating measure. A 2016 multi-center U.S. trial (302 non-patient subjects with recurring abdominal discomfort and bloating) found both the probiotic and placebo groups improved significantly, with no significant difference between them in either abdominal discomfort or bloating severity. A 2025 trial specifically in patients formally diagnosed with functional abdominal bloating (68 subjects, Rome IV criteria) found the same pattern: real improvement in both groups, no statistically significant probiotic-over-placebo difference once the analysis was corrected for testing multiple outcomes.
• Both trials found a real, substantial placebo response — a pattern the 2025 trial’s own authors explicitly named as “the strong placebo effect commonly observed” in trials of functional gastrointestinal disorders like bloating. This is a genuinely important, underappreciated fact for this specific symptom category: bloating fluctuates naturally and responds strongly to attention and expectation, which is exactly why a placebo-controlled design (not just “people who took it felt better”) is the only way to know if a specific product is actually doing anything beyond that.
• The 2016 trial did find one narrower positive signal: participants taking the probiotic had significantly more “bloating-free days” than the placebo group, even though their average symptom-severity scores weren’t significantly different. This is a real, disclosed finding — not nothing — but it’s a secondary measure, not the trial’s primary result, and it doesn’t override the null finding on the main bloating-severity outcome.
• Zoomed out to irritable bowel syndrome generally (a diagnosed condition for which bloating is one of several core symptoms — see this site’s companion article on distinguishing IBS/SIBO from ordinary “leaky gut” marketing language), the evidence picture is more encouraging but still not strain-specific enough to act on. Per NIH’s National Center for Complementary and Integrative Health (NCCIH), a 2018 review of 53 studies (5,545 participants) found probiotics “may have beneficial effects on global IBS symptoms and abdominal pain,” but the reviewers explicitly could not identify which species, strains, or combinations were most likely to help.
• The practical takeaway is not “probiotics definitely don’t help bloating” — it’s that the specific, most-marketed strain has real trial data behind it, and that data is a null result on its own primary bloating endpoint, twice. A product’s marketing citing “clinically studied” or “backed by research” for this exact use is technically accurate (the strain has indeed been studied for exactly this) while omitting that the studies didn’t clear their own bar for statistical significance on the main outcome.

The 2016 trial: 302 people, a real placebo effect, and a null primary result

A multi-center, double-blind, randomized, placebo-controlled trial conducted at ten U.S. clinical centers enrolled 302 subjects who were not patients under a doctor’s care for their symptoms — people experiencing abdominal discomfort and bloating at least twice a week for three months, but who hadn’t seen a physician or received prescribed medication for it, closer to the actual population buying an over-the-counter probiotic than a clinical trial population would typically be. After a 2-week placebo run-in phase, participants received either B. infantis 35624 or placebo for 4 weeks.

Both groups improved significantly on abdominal discomfort and bloating scores over the intervention period — itself a sign of how much these symptoms fluctuate and respond to simply being tracked and cared for. But comparing the two groups directly, mean symptom severity scores for both abdominal discomfort and bloating showed no significant difference between the probiotic and placebo arms. The one measure that did favor the probiotic group: more bloating-free days per week compared to placebo, a real and disclosed secondary finding, but not the trial’s primary endpoint and not sufficient on its own to call the trial a clear win for the product.

The 2025 trial: a more rigorously diagnosed population, the same pattern

A more recent triple-blind, randomized, placebo-controlled trial, published in November 2025, tightened the population definition considerably: participants had to meet the Rome IV diagnostic criteria for functional abdominal bloating specifically, not just self-reported recurring symptoms. Sixty-eight subjects received either B. infantis 35624 or placebo for 4 weeks (following a 2-week metronidazole run-in phase), with symptoms tracked across 8 weeks total and a statistical correction (Holm–Bonferroni) applied specifically to guard against false-positive findings from testing many symptom outcomes at once — a more statistically conservative approach than many older nutrition-supplement trials use.

The result: both the probiotic and placebo groups showed significant improvement in bloating, postprandial fullness, belching, nausea, regurgitation, and quality of life. The probiotic group additionally showed reductions in early satiety and flatulence not seen in the placebo group — but after the statistical correction for multiple comparisons, no significant between-group differences remained on any measure. The trial’s own authors concluded that B. infantis 35624 “did not significantly improve bloating, other abdominal symptoms, or QoL compared with placebo,” explicitly attributing much of the apparent improvement in both arms to the well-documented strong placebo response in trials of this type of condition.

The broader IBS picture: real signal, but not strain-specific enough to shop by

Bloating is also one of the core symptoms of irritable bowel syndrome, a diagnosed condition covered in more detail in this site’s companion article distinguishing real gut diagnoses from marketing language. Zoomed out to IBS trials generally (not just the two B. infantis 35624 trials above), the picture is somewhat more encouraging: per NCCIH’s own summary of the research, a 2018 review of 53 studies (5,545 participants) found that probiotics as a category “may have beneficial effects on global IBS symptoms and abdominal pain.” But the same review’s reviewers were explicit that they could not identify which specific species, strains, or combinations were most likely to help — which means this finding, while real, doesn’t translate into “buy any probiotic and expect bloating relief,” and it doesn’t specifically validate the strain most commonly marketed for bloating relief, which is exactly the strain the two dedicated trials above found no significant benefit from.

What we could not check

• We did not independently pull and read the full text of either the 2016 or 2025 B. infantis 35624 trials — findings above are drawn from each trial’s own published abstract (read directly for the 2025 trial; read via a secondary summary sourced from the original abstract for the 2016 trial, since PubMed’s abstract page was not directly accessible during this research pass).
• We did not independently verify the 2018 IBS probiotics review’s full methodology or its strain-by-strain breakdown — the 53-study, 5,545-participant figures and the “beneficial but not strain-identifiable” conclusion are drawn from NCCIH’s own summary of that review, the same source used in this project’s companion Probiotics 101 article.
• We did not review probiotic evidence for bloating outside the B. infantis 35624 and general-IBS research covered here — other bloating-marketed strains (certain Lactobacillus species, for instance) were not individually researched in this pass and may have different, strain-specific evidence not reflected in this article.
• This article does not evaluate SIBO (small intestinal bacterial overgrowth) specifically as a cause of bloating — that’s a distinct diagnosed condition covered in this site’s companion “leaky gut and contested terms” article, not folded into this one.

Our rating, and why

Limited, and the two most directly relevant trials of the specific bloating-marketed strain both returned null primary results. This isn’t the same as “probiotics don’t work for bloating” — the broader IBS literature shows a real if strain-unspecific signal, and one trial did find a genuine secondary benefit (more bloating-free days). But the strongest, most targeted, most recent evidence specifically testing the most commonly marketed bloating strain against its own primary endpoint, twice, found no significant advantage over placebo — a materially more cautious conclusion than “clinically studied for bloating” marketing language implies, and a good illustration of why reading a trial’s actual primary-outcome result matters more than knowing a trial exists at all.

Sources

1. National Center for Complementary and Integrative Health (NCCIH), National Institutes of Health. Probiotics: Usefulness and Safety. https://www.nccih.nih.gov/health/probiotics-usefulness-and-safety (read in full directly; same source used in this project’s Probiotics 101 article)
2. Ringel-Kulka T, et al. Multi-Center, Double-Blind, Randomized, Placebo-Controlled, Parallel-Group Study to Evaluate the Benefit of the Probiotic Bifidobacterium infantis 35624 in Non-Patients With Symptoms of Abdominal Discomfort and Bloating. American Journal of Gastroenterology. 2016. (read via the published abstract, sourced through a secondary summary; direct PubMed access was blocked during this research pass)
3. Hosseinian S-Z, Tabesh E, Alipour Z, Soheilipour M, et al. Efficacy of the Probiotic Bifidobacterium infantis 35624 in Functional Abdominal Bloating: A Triple-Blind, Randomized Controlled Trial. SN Comprehensive Clinical Medicine. 2025;7:369. https://link.springer.com/article/10.1007/s42399-025-02123-8 (abstract read directly)
4. Ford AC, Harris LA, Lacy BE, et al. Systematic review with meta-analysis: the efficacy of prebiotics, probiotics, synbiotics and antibiotics in irritable bowel syndrome. Alimentary Pharmacology & Therapeutics. 2018;48(10):1044-1060. (read via NCCIH’s summary, not the primary paper directly)