After analyzing over 40 probiotics across 69 trials, we’ve identified the most promising probiotics for managing diarrhea, constipation, and bloating 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, constipation, and bloating, supported by high-quality evidence from two key studies.

Study 1: Children with IBS

• For diarrhea, participants saw a 71% reduction in urgency, with scores improving from 3.1 to 0.9 after 8 weeks. This suggests a strong benefit (effect size: 1.10).
• Constipation relief was also significant, with incomplete evacuation improving by 73.3% and straining by 70%, both showing strong effect sizes (1.19).
• Bloating improved dramatically, with an 80% reduction over 8 weeks. The average score dropped from 3.0 to 0.6 on a 5-point scale (effect size: 1.88), and participants reported noticeable relief in abdominal bloating (p < 0.0001). (1)

Study 2: Adults with IBS

• Diarrhea symptoms, specifically urgency, improved by 56.7%, with scores dropping from 3.0 to 1.3 over 8 weeks (effect size: 1.26).
• Constipation also improved, with a 61.3% reduction in incomplete evacuation and a 65% improvement in straining (effect sizes: 1.55 and 1.67, respectively).
• Bloating saw a significant decrease, with scores dropping from 3.4 to 1.4 on a 6-point scale, marking a 58.8% improvement (effect size: 1.42). (2)

Our Criteria

The probiotics in our full database (below) are automatically ranked based on their 1) effect size for diarrhea, constipation, and bloating 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, constipation, and bloating 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, constipation, and bloating 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.