After analyzing over 40 probiotics across 69 trials, we’ve identified the most promising probiotics for managing diarrhea and pain 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)

Lactospore

Diarrhea:In a small study of adults with IBS-D, Lactospore significantly improved diarrhea symptoms. Over 90 days, participants saw a 45.1% reduction in stool frequency and improved stool consistency, with a strong effect size (Cohen’s d of 2.93) for stool frequency and 1.30 for overall diarrhea reduction. (1)

Pain Relief: The same study found Lactospore significantly reduced abdominal pain and GI discomfort, with a 68.1% decrease in pain (p=0.0001) and a large effect size of 2.5. (1) A later study on adults with major depressive disorder and IBS also showed moderate improvements in GI discomfort (effect size 0.68). (2)
Overall, Lactospore earned a composite score of 1.46 for relieving IBS-related abdominal pain and discomfort, securing its spot as our top choice for diarrhea and IBS pain relief.

Unique IS-2 

Diarrhea: Bacillus coagulans Unique IS-2 was tested in both children and adults with IBS, showing significant improvements in urgency, a symptom closely linked to diarrhea. In adults, urgency improved by 56% (effect size = 1.26), (3) while in children, urgency improved by 71% (effect size = 1.10). (4)

Pain: Across both studies, Unique IS-2 also demonstrated notable pain relief. In children, 81.94% of participants reported over 50% pain relief after 4 weeks, increasing to 93.06% by 8 weeks (effect size = 1.88).(4) In adults, pain intensity decreased by 58.5%, with 84.91% of participants achieving at least 50% pain relief by week 8. (3) Abdominal discomfort also decreased by 63.9%, with a large effect size of 1.73. These findings earned Unique IS-2 the #2 spot in our rankings.

I.31 

Diarrhea: In a clinical trial on the probiotic I.31, participants with IBS-D and IBS-M, recruited during a diarrheal phase, experienced significant improvements in stool consistency, shifting from diarrhea to normal stools. (5) The effect size for diarrhea symptoms was particularly high (Cohen’s d = 3.3). However, its impact on global IBS symptoms was neutral, showing no significant overall improvement.

Pain: The same study found that I.31 significantly reduced abdominal pain, with 38.9% of patients reporting improvement. The effect size for pain relief was large (Cohen’s d = 1.33, p < 0.05), further supporting I.31’s efficacy in managing IBS-related symptoms. (5) These results earned I.31 the #3 spot in our rankings for diarrhea and pain relief.

Bio-Kult

Diarrhea: In one of the largest IBS probiotic trials involving 360 IBS-D patients, Bio-Kult led to a substantial decrease in daily bowel movements, with the average dropping from 6.1 to 2.5 per day. (6) The effect size for diarrhea reduction was substantial (Cohen’s d = 0.92).

Pain: By the end of month 4, Bio-Kult significantly reduced abdominal pain, with pain scores dropping by 69% from baseline. (6)The effect size for pain reduction was moderate (Cohen’s d = 0.72, p < .001), earning Bio-Kult the #4 spot for diarrhea and pain relief in IBS.

Our Criteria

The probiotics in our full database (below) are automatically ranked based on their 1) effect size for diarrhea and pain 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 pain 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. The probiotics we’ve featured here have shown promise for diarrhea and pain 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 the above parameters.
*Effect sizes are reported as the weighted mean effect size across studies.

References

1. Majeed, M., Nagabhushanam, K., Natarajan, S. et al. Bacillus coagulans MTCC 5856 supplementation in the management of diarrhea predominant Irritable Bowel Syndrome: a double blind randomized placebo controlled pilot clinical study. Nutr J 15, 21 (2015). https://doi.org/10.1186/s12937-016-0140-6
2. Majeed M, Nagabhushanam K, Arumugam S, Majeed S, Ali F. Bacillus coagulans MTCC 5856 for the management of major depression with irritable bowel syndrome: a randomised, double-blind, placebo controlled, multi-centre, pilot clinical study. Food Nutr Res. 2018 Jul 4;62. doi: 10.29219/fnr.v62.1218. PMID: 29997457; PMCID: PMC6034030.
3. 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. 
4. Sudha MR, Jayanthi N, Aasin M, et al. Efficacy of Bacillus coagulans Unique IS2 in treatment of irritable bowel syndrome in children: a double blind, randomised placebo controlled study. Benef Microbes 2018;9(4):563–72. doi: 10.3920/BM2017.0129.
5. Diego A. Barraza-Ortiz, Nuria Pérez-López, Víctor M. Medina-López, José I. Minero-Alfaro, Felipe Zamarripa-Dorsey, Nerina del C. Fernández-Martínez, Alberto Llorente-Ramón, Gustavo A. Ramos-Aguilar; Combination of a Probiotic and an Antispasmodic Increases Quality of Life and Reduces Symptoms in Patients with Irritable Bowel Syndrome: A Pilot Study. Dig Dis 11 May 2021; 39 (3): 294–300.
6. Ishaque SM, Khosruzzaman SM, Ahmed DS, Sah MP. A randomized placebo-controlled clinical trial of a multi-strain probiotic formulation (Bio-Kult®) in the management of diarrhea-predominant irritable bowel syndrome. BMC Gastroenterol 2018 May 25;18(1):71. [doi: 10.1186/s12876-018-0788-9]

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.