After analyzing over 40 probiotics across 69 trials, we’ve identified the most promising probiotics for managing diarrhea and gas in IBS. Our dataset (below) is ordered based on an automated scoring system, which we further refined using additional criteria (below) to select our top choices. Here are the results of our findings.

Our Top Choice(s)

Bacillus coagulans Unique IS-2 emerged as the most promising probiotic for managing diarrhea and gas (flatulence), supported by high-quality evidence from two key studies.

Study 1: Children with IBS

• In this 8-week study, children experienced a 71% improvement in diarrhea-related urgency, with scores decreasing from 3.1 to 0.9 (effect size: 1.10). Additionally, gas symptoms saw a significant 76.5% reduction, with scores dropping from 3.4 to 0.8 (effect size: 1.21), indicating a strong benefit for both symptoms.(1)

Study 2: Adults with IBS

• In adults, diarrhea urgency improved by 56.7%, with scores dropping from 3.0 to 1.3 over 8 weeks (effect size: 1.26). Gas symptoms also showed notable improvement, decreasing by 62.5%, with scores reducing from 3.2 to 1.2 (effect size: 1.72), showing a particularly strong impact. (2)

These findings highlight Bacillus coagulans Unique IS-2 as a top choice for alleviating diarrhea and gas in both children and adults with IBS, with consistently strong effect sizes across studies.

Our Criteria

The probiotics in our full database (below) are automatically ranked based on their 1) effect size for diarrhea and gas relief, followed by 2) effect size for overall IBS symptoms (‘Global IBS Symptoms’), and finally by 3) the quality of evidence from the studies.

For this summary, we selected our top choices based on these rankings, along with the following additional criteria: 

• Evidence Quality Score: We only included probiotics backed by studies with an evidence quality score of 75% or higher.
• Effect Size: Only probiotics that demonstrated a moderate to high effect size (>0.5) for diarrhea and gas relief made the cut.
• Clear Dosing Information: Only probiotics with clear and reliable dosing data were included.
• Commercial Availability: Probiotics needed to be commercially available to consumers.

No Direct Comparisons

It’s important to note that there are no direct comparisons between the probiotics in our database across identical study methods, so we can’t definitively rank one probiotic as superior to another. Bacillus coagulans Unique IS-2 shows promise for diarrhea and gas relief in IBS, but as with all probiotic supplements, always consult your healthcare provider before starting.

*Population values represent the per protocol population size from studies specifically assessing a gas-related parameter.
*Effect sizes are reported as the weighted mean effect size across studies.

References

1. Sudha MR, Jayanthi N, Aasin M, et al. Efficacy of Bacillus coagulans Unique IS2 in the treatment of irritable bowel syndrome in children: a double-blind, randomised placebo-controlled study. Benef Microbes. 2018;9(4):563-572. doi:10.3920/BM2017.0129.
2. Madempudi RS, Ahire JJ, Neelamraju J, et al. Randomized clinical trial: the effect of probiotic Bacillus coagulans Unique IS2 vs. placebo on the symptoms management of irritable bowel syndrome in adults. Sci Rep. 2019;9:12210. doi:10.1038/s41598-019-48554-x.

When selecting our top probiotic picks, we ensure they are commercially available and backed by high-quality evidence, with an average score above 75% for the relevant symptom parameters. The probiotics must also demonstrate a moderate to high effect size (>0.5) for these symptoms. If there are more than five candidates, we limit our top picks to the best five based on the effect size for relevant symptoms and Global IBS symptoms, as well as evidence quality. This ensures our recommendations are practical and reliable.

When selecting our top probiotic picks, we ensure they are commercially available and backed by high-quality evidence, with an average score above 75% for the relevant symptom parameters. The probiotics must also demonstrate a moderate to high effect size (>0.5) for these symptoms. If there are more than five candidates, we limit our top picks to the best five based on the effect size for relevant symptoms and Global IBS symptoms, as well as evidence quality. This ensures our recommendations are practical and reliable.