Research project led by Bailey Hanna, MS, RDN - no affiliate links, ads or sponsored products.
Of all the probiotics we assessed, Bacillus coagulans Unique IS-2 was a true stand out. This probiotic was tested in two randomized, placebo-controlled trials—one with children (1) (n = 141) and another with adults (2) (n = 108). Both studies provided Bacillus coagulans Unique IS-2 at a dose of 2 billion colony-forming units (CFU) per day for 8 weeks, evaluating symptoms such as bowel habits, overall IBS symptom severity, and abdominal pain intensity.
Why Did Unique IS-2 Catch Our Attention?
Findings from the Studies
*All p-values are in comparison to a placebo control after treatment.
Additional Significant Improvements
Were There Subtype-Specific Effects?
In both studies, no subtype-specific analysis was conducted, so the results are generalized across the subtypes assessed. In the children’s study, the population was mainly IBS-C (51.77%), followed by IBS-D (41.13%) and IBS-M (7.24%).1 In the adult study, the population consisted of IBS-M (66.04%) and IBS-C (33.96%), with no IBS-D participants.2 It’s possible that Bacillus coagulans Unique IS-2 may have therapeutic effects in IBS-D, IBS-C, and IBS-M populations, though future subtype-specific studies would help in confirming these benefits.
Key Takeaways
Available evidence suggests that Bacillus coagulans Unique IS-2 is a promising probiotic candidate for managing a broad range of IBS symptoms, including abdominal pain, incomplete evacuation, global IBS symptoms, abnormal bowel habits, bloating/distention, and flatulence. The studies on this probiotic fell into our highest tier for evidence quality, and the composite beneficial effects all fell into our strongest effect size category of ≥ 1.0. Overall, Bacillus coagulans Unique IS-2 has shown great potential for improving IBS symptoms across diverse IBS populations.
Dosing Instructions:
Trial Duration
References:
Evaluate products based on whether they transparently disclose all ingredients and their amounts, exclusively use probiotics tested in randomized placebo-controlled trials in IBS populations, and contain studied doses.
This probiotic has higher quality studies in IBS populations supporting it. View our evidence evaluation framework to learn how we assess the quality of studies.
Add condition
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
CHILDREN 4-12 years
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
ADULTS 18-60 years
Urgency Improvement: The probiotic group exhibited significant improvements in managing bowel movement urgency. Initially, participants in the probiotic group reported a mean score of 3.1 (with a standard deviation of 0.9) on a 1-5 Likert scale.
After 8 weeks of treatment, this mean score was notably reduced to 0.9 (0.81 SD), reflecting a 71.0% improvement from baseline. The effect size for this reduction, calculated as Cohen’s h, was 1.10, indicating a strong effect.
Placebo Group Comparison: The placebo group also experienced some improvement, but to a lesser extent. Their mean score decreased from 3.1 (0.71 SD) to 1.9 (1.00 SD) over the same period, which corresponds to a 39.7% reduction from baseline.
The difference in improvement between the probiotic and placebo groups was statistically significant (p < 0.0001), according to the Wilcoxon-Mann-Whitney test for two independent groups.
Incomplete Evacuation: In this study, the probiotic group demonstrated impressive improvements in the sensation of incomplete evacuation. Initially, this group had a mean score of 3.0 (with a standard deviation of 0.64) on a 1-5 Likert scale.
By the end of the 8-week treatment period, the mean score significantly dropped to 0.8 (0.77 SD), representing a 73.3% improvement from baseline. The effect size for this change, calculated as Cohen’s h, was 1.19, indicating a strong effect.
The placebo group, on the other hand, experienced a lesser reduction. Their mean score decreased from 3.2 (0.63 SD) to 1.8 (0.90 SD) over the same period, which equates to a 43.8% reduction from baseline.
The difference between the probiotic and placebo groups was statistically significant (p < 0.0001), as determined by the Wilcoxon-Mann-Whitney test for two independent groups. Straining Similarly, the probiotic group showed significant reductions in straining during bowel movements.
At the start of the study, the mean score for straining was 3.0 (0.96 SD). By the end of the treatment, this score was reduced to 0.9 (0.83 SD), marking a 70.0% improvement from baseline.
The effect size here was also strong, with a Cohen’s h of 1.19. In comparison, the placebo group saw a reduction from a mean score of 3.1 (0.86 SD) to 2.0 (1.00 SD), a 35.4% decrease. This difference between the groups was statistically significant (p < 0.0001).
When it comes to bowel habit satisfaction, the results from this study were quite compelling. The group receiving probiotics started with an average score of 3.1 (with a standard deviation of 0.60) on a 1-5 Likert scale.
By the end of the 8-week treatment, this score dramatically dropped to 0.9 (1.02 SD), marking a substantial 71.0% mean improvement from baseline. We calculated an effect size (Cohen’s h) of 1.37, placing this parameter in our strongest effect size category.
In contrast, the placebo group saw a relative mean reduction of only 25.8%. They started with a baseline mean score of 3.1 (0.64 SD) and ended with a score of 2.3 (1.02 SD) at week 8.
This difference was statistically significant compared to the placebo group (p < 0.0001), as confirmed by the Wilcoxon-Mann-Whitney test for two independent groups.
Improvement in Stool Consistency: From the 6th week of treatment onwards, a significant improvement in stool consistency was noted among the probiotic group. Nearly 50% of the patients achieved normal stool consistency, with 38 out of 72 patients attaining this goal. This improvement yielded a moderate effect size of 0.73.
Additionally, the probiotic group exhibited significant improvement on the Subject’s Global Assessment of Relief (SGARC) scale for the number and characteristics of stools from baseline to week 8 (p < 0.0001).
The probiotic group experienced significant improvements in the overall assessment of IBS score. Initially, this group had a mean score of 3.3 (with a standard deviation of 0.51) on a 1-5 Likert scale.
By the end of the 8-week treatment, this mean score was reduced to 1.3 (0.78 SD), reflecting a 60.6% mean improvement from baseline. The effect size for this improvement, calculated as Cohen’s h, was 1.08, indicating a strong effect.
Placebo Group Comparison: The placebo group also saw some improvement, but to a lesser extent. Their mean score decreased from 3.3 (0.50 SD) to 2.2 (0.87 SD), corresponding to a 33.3% mean reduction from baseline. The difference between the probiotic and placebo groups was statistically significant (p < 0.0001), according to the Wilcoxon-Mann-Whitney test for two independent groups.
Total Score: In addition to the overall assessment, the probiotic group also showed a significant reduction in their total symptom score. Initially, the mean baseline score was 25.3 (3.16 SD). This score was reduced to 6.7 (4.43 SD) by the end of the 8-week treatment, representing a 73.4% mean improvement from baseline.
The effect size here was even more pronounced, with a Cohen’s h of 2.03. The placebo group experienced a reduction in total score from 25.6 (2.82 SD) to 16.9 (5.53 SD), a 34.0% mean reduction. Again, the change was statistically significant compared to the placebo group (p < 0.0001).
Global Relief Assessment: The probiotic group also showed significant improvement on the Subject’s Global Assessment of Relief (SGARC) scale. This scale measured relief of symptoms over the last week as well as total SGARC scores, and the probiotic group demonstrated significant improvements for each of these assessments (p < 0.0001 for both).
The effect size for the SGARC global assessment of relief was Cohen’s h = 2.08, indicating a very strong effect.
Pain Relief After 4 and 8 Weeks: The study revealed substantial pain relief among participants in the probiotic group compared to the placebo group:
After 4 Weeks: Probiotic Group: 59 out of 72 patients (81.94%) reported more than 50% relief from pain on an 11-point scale (0-10). Placebo Group: 33 out of 69 patients (47.83%) reported more than 50% relief. Statistical Significance: The difference was highly significant (chi-square test, P < 0.001).
After 8 Weeks: Probiotic Group: 67 out of 72 patients (93.06%) were categorized as responders. Placebo Group: Only 15 out of 69 patients (21.74%) were categorized as responders. Statistical Significance: The difference was highly significant (chi-square test, P < 0.001), with an effect size (Cohen’s h) of 0.97.
Reduction in Abdominal Discomfort The probiotic group also showed significant improvement in reducing abdominal discomfort: Initial Scores: The probiotic group had a mean score of 3.4 (0.70 SD) on a 1-5 Likert scale.
After 8 Weeks: This mean score was reduced to 0.5 (0.82 SD), an 85.29% reduction from baseline. The effect size (Cohen’s h) was 1.88, indicating a very strong effect. Placebo Group: Experienced a mean score reduction from 3.6 (0.67 SD) to 2.4 (1.19 SD), a 33.3% reduction. Statistical Significance:
The change in the probiotic group was significantly greater than in the placebo group (p < 0.0001, Wilcoxon-Mann-Whitney test for two independent groups).
Global Relief Assessment Significant improvements were also noted on the Subject’s Global Assessment of Relief (SGARC) scale, particularly in the frequency and intensity of abdominal pain and discomfort from baseline to week 8 (p < 0.0001).
The probiotic group showed substantial improvement in symptoms of bloating. Initially, this group had a mean score of 3.0 (with a standard deviation of 0.92) on a 1-5 Likert scale.
By the end of the 8-week treatment period, the mean score significantly decreased to 0.6 (0.78 SD), marking an impressive 80.0% improvement from baseline. The effect size for this change, calculated as Cohen’s h, was 1.88, indicating a very strong effect.
Placebo Group Comparison: The placebo group also experienced some reduction in bloating, but it was much less pronounced. Their mean score dropped from 3.1 (0.91 SD) to 2.2 (0.91 SD), which translates to a 29.0% reduction from baseline. This difference between the probiotic and placebo groups was statistically significant (p < 0.0001), as determined by the Wilcoxon-Mann-Whitney test for two independent groups.
Global Relief Assessment: In addition to the significant reduction in bloating, the probiotic group also showed marked improvement on the Subject’s Global Assessment of Relief (SGARC) scale for abdominal bloating or gassiness, where the probiotic group demonstrated significant improvement from baseline to week 8 (p < 0.0001).
Improvement in Passage of Gas The probiotic group demonstrated notable improvements in “passage of gas.” Initially, this group had a mean score of 3.4 (with a standard deviation of 0.8) on a 1-5 Likert scale.
By the end of the 8-week treatment, this mean score was significantly reduced to 0.8 (0.80 SD), representing a 76.5% mean improvement from baseline. The effect size for this reduction, calculated as Cohen’s h, was 1.21, indicating a strong effect.
Placebo Group Comparison: The placebo group also experienced some improvement, but it was less pronounced. Their mean score decreased from 3.3 (0.56 SD) to 1.9 (1.00 SD), which corresponds to a 42.4% mean reduction from baseline.
This difference between the probiotic and placebo groups was statistically significant (p < 0.0001), as determined by the Wilcoxon-Mann-Whitney test for two independent groups.
Global Relief Assessment: The probiotic group also showed significant improvement on the Subject’s Global Assessment of Relief (SGARC) scale for abdominal bloating or gassiness from baseline to week 8 compared to placebo (p < 0.0001).
No data
Family Impact Assessment: The study demonstrated that the probiotic group experienced significant improvements on the Subject’s Global Assessment of Relief (SGARC) scale, particularly in terms of the family’s assessment of the impact of their child’s IBS on the family’s life.
Probiotic Group: Showed a significant reduction in the perceived impact from baseline to week 8. Statistical Significance: This change was highly significant (p < 0.0001).
The findings from this study are applicable to a pediatric population. For younger children, symptom improvements were reported by parents, while older children provided self-reports.
Urgency was assessed using an IBS severity scoring system on a 6-point Likert scale. The probiotic group had a mean baseline score of 3.0 (±0.48 SD) and saw an improvement to a mean score of 1.3 (±0.89 SD) by week 8, reflecting a relative mean decrease of 56.7% (Cohen’s h = 1.26, indicating a large effect size).
In comparison, the placebo group started with a mean baseline score of 3.1 (±0.57 SD) and improved to 2.5 (±1.00 SD) at week 8, resulting in a relative mean decrease of 19.3%. The difference between the groups was statistically significant (p < 0.0001).
Incomplete evacuation was analyzed via an IBS severity scoring system (6-point Likert scale). The probiotic group had a mean baseline score of 3.1 (0.36 SD) with a week 8 mean score of 1.2 (0.76 SD), which was a relative mean improvement of 61.3%. (Cohen’s h = 1.55).
The placebo group had a mean baseline score of 3.2 (0.45 SD) with a week 8 mean score of 2.5 (0.90 SD), which was a relative mean decrease of 21.9%. The difference between groups was statistically significant at week 8 (p <0.0001). Straining was also analyzed via an IBS severity scoring system (6-point Likert scale).
The probiotic group had a mean baseline score of 3.2 (0.49 SD) with a week 8 mean score of 1.1 (0.65 SD), which was a relative mean improvement of 65.6%. (Cohen’s h = 1.67). The placebo group had a mean baseline score of 3.2 (0.51 SD) with a week 8 mean score of 2.5 (0.98 SD), which was a relative mean decrease of 21.9%. The difference between groups was statistically significant (p <0.0001).
—– Incomplete evacuation was assessed using an IBS severity scoring system on a 6-point Likert scale. The results for the probiotic group were quite impressive: they started with a mean baseline score of 3.1 (±0.36 SD) and improved to 1.2 (±0.76 SD) by week 8, marking a significant improvement of 61.3% from baseline. We calculated a large effect size, Cohen’s h, of 1.55 for this parameter.
In contrast, the placebo group started at 3.2 (±0.45 SD) and only improved to 2.5 (±0.90 SD), a 21.9% improvement. The difference between groups at week 8 was statistically significant (p < 0.0001).
Bowel Habit Satisfaction Researchers used an IBS severity scoring system (a 6-point Likert scale) to measure bowel habit satisfaction. Here’s how the groups compared:
Probiotic Group:
Baseline Score: 3.3 (±0.63 SD)
Week 8 Score: 1.4 (±0.74 SD)
Relative Mean Improvement: 57.6%
Cohen’s h: 1.84 (indicating a large effect size)
Placebo Group:
Baseline Score: 3.4 (±0.63 SD)
Week 8 Score: 2.9 (±0.87 SD)
Relative Mean Improvement: 14.7%
The improvement in the probiotic group was statistically significant (p < 0.0001), showing a much greater improvement in bowel habit satisfaction compared to the placebo group.
Stool Consistency: After 6 weeks of treatment, the probiotic results were impressive for improvements in stool consistency: Probiotic Group: 65% (36 out of 53 patients) achieved normal stool consistency. Placebo Group: Only 32.72% (18 out of 55 patients) achieved normal stool consistency. The difference was statistically significant (p < 0.001).
The “Overall assessment” was evaluated using an IBS severity scoring system on a 6-point Likert scale. The probiotic group started with a mean baseline score of 3.6 (±0.57 SD) and improved to a mean score of 1.6 (±0.86 SD) by week 8, reflecting a relative mean decrease of 55.6% (Cohen’s h = 1.65, indicating a large effect size).
Meanwhile, the placebo group had a mean baseline score of 3.6 (±0.53 SD) and only improved to 3.0 (±0.83 SD) by week 8, showing a relative mean decrease of 16.7%. The difference between the groups was statistically significant (p < 0.0001).
Patient global assessment results for the B. coagulans group (n = 53) revealed that 10 patients (18.87%) experienced complete relief from IBS symptoms, and 34 patients (64.15%) had considerable relief. This was significantly higher (p < 0.0001) compared to the placebo group (n = 55), where no patients (0%) had complete relief and only 6 patients (10.91%) experienced considerable relief.
Similarly, physician global assessment showed that 11 patients (20.75%) in the B. coagulans group (n = 53) experienced complete relief, and 31 patients (58.49%) had considerable relief from IBS symptoms. In contrast, the placebo group (n = 55) had no patients (0%) with complete relief and only 6 patients (10.91%) with considerable relief.
At the end of week 8, the mean baseline pain intensity score on an 11-point Numerical Rating Scale (NRS) was reduced from 8.2 ± 1.37 to 3.4 ± 2.08 in the B. coagulans Unique IS-2 treated group, representing a significant relative mean decrease of 58.5% (Cohen’s h = 1.64).
In contrast, the placebo group saw a reduction from 8.3 ± 1.25 to 6.7 ± 1.92, a relative mean decrease of 19.3% (two-sample t-test, p < 0.001). Patients showing a ≥50% reduction in pain from their baseline visit were considered responders.
At week 4, 5 (9.43%) patients in the B. coagulans Unique IS-2 group (n = 53) and 2 (3.64%) patients in the placebo group (n = 55) had achieved this level of pain reduction. By week 8, a substantial 45 (84.91%) patients in the probiotic group and only 7 (12.73%) in the placebo group showed ≥50% pain reduction (chi-square test, p < 0.001).
This trend continued at week 10, with 48 (90.57%) patients in the probiotic group and 6 (10.91%) in the placebo group demonstrating ≥50% pain reduction (chi-square test, p < 0.001). Abdominal discomfort was also evaluated using an IBS severity scoring system on a 6-point Likert scale.
The probiotic group had a mean baseline score of 3.6 (±0.60 SD) which improved to 1.3 (±0.85 SD) by week 8, reflecting a relative mean decrease of 63.9% (Cohen’s h = 1.73). The placebo group had a mean baseline score of 3.6 (±0.56 SD) and improved to 2.8 (±0.87 SD), a relative mean decrease of 22.2%. The difference between the groups was statistically significant (p < 0.0001).
Bloating and distension were assessed using an IBS severity scoring system on a 6-point Likert scale. The probiotic group started with a mean baseline score of 3.4 (±0.75 SD) and improved to a mean score of 1.4 (±0.80 SD) by week 8, showing a relative mean decrease of 58.8% (Cohen’s h = 1.42, indicating a large effect size).
In contrast, the placebo group had a mean baseline score of 3.3 (±0.58 SD) and saw a week 8 mean score of 2.7 (±1.00 SD), resulting in a relative mean decrease of 18.2%. The difference between the groups was statistically significant (p < 0.0001).
“Passage of gas” was assessed using an IBS severity scoring system on a 6-point Likert scale. The probiotic group started with a mean baseline score of 3.2 (±0.60 SD) and improved to a mean score of 1.2 (±0.76 SD) by week 8, showing a relative mean decrease of 62.5% (Cohen’s h = 1.72, indicating a large effect size).
In contrast, the placebo group had a mean baseline score of 3.3 (±0.53 SD) and saw a week 8 mean score of 2.6 (±0.85 SD), resulting in a relative mean decrease of 21.2%. The difference between the groups was statistically significant (p < 0.0001).
Throughout the study, hematological values remained normal. There were no significant changes in either pro-inflammatory cytokines (IL-6, IL-12, TNF-α, INF-γ) or the anti-inflammatory cytokine (IL-10) levels at the end of the 8-week B. coagulans treatment when compared to the placebo.