Bacillus coagulans, Bacillus subtilis and Spore-Forming Probiotics: How They Differ and What Is Known
Spore-forming probiotics (Bacillus coagulans, B. subtilis, B. clausii): how they differ from lactobacilli, what named-strain trials found, safety questions and what "soil-based" means.
Content last updated . This page has not been medically reviewed.
What is Bacillus coagulans, Bacillus subtilis and spore-forming probiotics good for?
What the body uses it for, and how strong the evidence is. A normal job in the body is not proof that extra supplements add benefit; each card says which.
Irritable bowel syndrome symptoms (named B. coagulans strains)
Preliminary or mixedIn single trials, B. coagulans Unique IS2 and BCP92 gave better abdominal pain or stool results than placebo in adults with IBS, while another strain (BC300) showed no difference during treatment.
Supplements: Small to medium single trials; results cannot be transferred to other strains or products. Guidelines (WGO 2023) say efficacy evidence for spore-formers lags behind other probiotics.
Functional dyspepsia (B. coagulans MY01 + B. subtilis MY02)
Preliminary or mixedA small pilot trial in 68 adults reported more responders on a two-strain spore-former mix than on placebo.
Supplements: Pilot study only; needs larger confirmation.
Bloating, burping and gas (B. subtilis BS50)
Preliminary or mixedIn a trial of healthy adults, more people improved on a bloating and gas score with B. subtilis BS50 than with placebo.
Supplements: Single trial; effect applies to that strain only.
Survival of spores through shelf life
Lab or animal research onlySpores are a tough dormant stage, so spore-formers resist storage stress better than many other probiotics. WGO says this does not mean proven benefit.
Supplements: Stability is a product feature, not a health benefit.
Children's acute diarrhea (B. clausii)
Preliminary or mixedA meta-analysis of six trials in 1,298 children reported diarrhea about 9 hours shorter with B. clausii.
Supplements: Modest effect in a small body of trials; not a replacement for rehydration.
Antibiotic-associated diarrhea (B. clausii strains)
Preliminary or mixedA 2025 review of four studies reported fewer cases with named B. clausii strains; the evidence base was small.
Supplements: Small evidence base; strain-specific.
Chronic constipation
Preliminary or mixedA 2022 meta-analysis found no significant stool-frequency effect for B. coagulans Unique IS2, while another probiotic (B. lactis) did show one.
Supplements: No clear benefit shown for this strain in constipation.
Immune and gut-lining effects (laboratory and mechanism research)
Lab or animal research onlyReviews describe possible effects on immune signalling and the gut in laboratory work; these have not been shown to give a benefit in people.
Supplements: No human benefit shown from mechanism studies alone.
Connected topics
Open a group to see how each topic connects and how strong the evidence is.
Health goals (2)
- Digestive SupportPreliminary or mixed
Single trials of named Bacillus strains (for example B. coagulans Unique IS2) report fewer gut symptoms than placebo in some adults with IBS, but results differ between strains and trials and cannot be pooled.
- Gut HealthPreliminary or mixed
Named strains were tested for gut symptoms in IBS, functional dyspepsia and bloating, with mixed or small trials; the general phrase 'gut health' is not a proven benefit of spore-formers as a group.
Body systems (2)
- Digestive SystemPreliminary or mixed
The trials of named Bacillus strains were on digestive symptoms (IBS, dyspepsia, bloating), with small or mixed results.
- Gut HealthPreliminary or mixed
The trials of named Bacillus strains were all on gut symptoms. Results are strain-specific and mixed.
Body parts (1)
- GutPreliminary or mixed
Studied for symptoms arising in the gut; results belong to the named strain only.
Functional actions (1)
- Digestive SupportPreliminary or mixed
Single trials of named Bacillus strains (for example B. coagulans Unique IS2) report fewer gut symptoms than placebo in some adults with IBS, but results differ between strains and trials and cannot be pooled.
Conditions & symptoms (1)
- Irritable Bowel SyndromePreliminary or mixed
Several named B. coagulans strains beat placebo for IBS symptoms in single trials, one three-arm trial differed from placebo only at follow-up; NCCIH says definite conclusions cannot be drawn for probiotics generally.
Names
Species names have changed. A 2026 review notes that Bacillus and related genera, Alkalihalobacillus and Heyndrickxia, are used as probiotics because they form endospores. [2] A 2024 trial title writes Bacillus coagulans as Heyndrickxia coagulans. [3] Older papers use the old names, so check both. About "soil-based": the term is not defined in the sources we read, so treat it as a marketing phrase and look for genus, species and strain code instead. See reading a probiotic label.Evidence labels used below: promising but limited, mixed, insufficient evidence. They are our plain summaries of each source.
What named strains were tested for
| Strain | Who and how long | What the source found | Label |
|---|---|---|---|
| B. coagulans Unique IS2 | 136 adults with IBS (Rome III), 2 billion CFU, 8 weeks | Better than placebo for abdominal pain and complete spontaneous bowel movements; no severe adverse events. [4] | Promising but limited |
| B. coagulans BC300 and B. lactis BI040 | 123 adults with IBS, 12 weeks | The groups did not differ from placebo during the 12 weeks; at week 16 follow-up more people in the B. coagulans group improved (52.9% vs 20.5%). [5] | Mixed |
| B. coagulans BCP92 | 100 adults with IBS, 12 weeks | Improved IBS severity and stool consistency against control. [3] | Promising but limited |
| B. coagulans MTCC 5856 | Adults with IBS with diarrhea (WGO table) | WGO lists fewer bloating, pain and diarrhea symptoms in a single trial [6]; a 2026 meta-analysis found better quality of life. [7] | Promising but limited |
| B. coagulans Unique IS2 and constipation | Chronic constipation in adults | A 2022 review found no significant stool-frequency effect for it, while B. lactis had one. [8] | Mixed |
| B. coagulans MY01 + B. subtilis MY02 | 68 adults with functional dyspepsia, 8 weeks | 48% vs 20% responders; a small exploratory pilot. [9] | Promising but limited |
| B. subtilis BS50 | 76 healthy adults, 6 weeks, 2 x 10^9 CFU | More people improved on a bloating, burping and gas score (47.4% vs 22.2%). [10] | Promising but limited |
| B. clausii | Six trials, 1,298 children with acute diarrhea | Diarrhea about 9 hours shorter and hospital stay about 0.85 days shorter. [11] | Promising but limited |
| B. clausii (four named strains) | Preventing antibiotic-associated diarrhea | A 2025 review of four studies reported fewer cases; the evidence base was small. [12] | Promising but limited |
WGO also lists B. clausii with H. pylori treatment, where it reduced treatment side effects (level 2). [6] The 2026 IBS review found conflicting or no efficacy for some other strains, which shows why names matter. [7] Do not pool the rows: a result for one Bacillus strain says nothing about another.
Amounts used in studies
Trial amounts above are study amounts, not advice. WGO says dose should rest on human studies of the specific product. [1] For product testing see quality testing and certifications.Frequently asked questions
Are spore-forming probiotics better than other probiotics?
Spores help survive shelf life, but WGO says evidence of efficacy lags behind other probiotics. [1]
What does "soil-based" mean?
The sources we read do not define it. Check the genus, species and strain on the label instead.
Is Bacillus coagulans the same as Lactobacillus?
No. Bacillus is a different genus that forms spores; WGO describes both as probiotics used in products. [1]
Do spore probiotics help IBS?
Several named strains beat placebo in single trials, and one three-arm trial showed a difference only at the week-16 follow-up. [4][5]
Who should avoid them?
People with severe illness or weakened immunity should ask a clinician first. [15]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety questions
- A 2022 review called these organisms "benefits with concerns" and asked about safety and the role of spore formation. [13]
- A 2017 review urged judging safety strain by strain. [14]
- A 2026 review lists limits: safety concerns, dose standardization, quality control and risks in immunocompromised people. [2]
- NCCIH says harm is more likely in severe illness or weakened immunity, and that some products contain organisms not on the label. [15] The 2023 ISAPP paper says species without a history of safe use need case-by-case safety review. [16]
- Proper evidence not found for these strains in pregnancy, breastfeeding, kidney or liver disease or before surgery (searched: WGO, NCCIH, NHS and the trial abstracts above). Ask a clinician; see pregnancy and breastfeeding and supplements before surgery.
- Medicine interactions are not described in these sources; ask a pharmacist (medication interactions).
- Children's diarrhea that is bloody, lasts over 7 days or brings dehydration signs needs medical care first. [17]
References
- World Gastroenterology Organisation. WGO Global Guideline: Probiotics and prebiotics. February 2023. Read 2026-10-22.
- Spore-Forming Probiotics and Their Mechanisms of Action: A Particular Focus on Alkalihalobacillus clausii (Mazzantini D, Ghelardi E. Nutrients 2026). PMID 42123979. Read 2026-10-22.
- Role of Bacillus coagulans (Heyndrickxia coagulans) BCP92 in managing irritable bowel syndrome: a randomized, double-blind, multicenter, placebo-controlled clinical trial (Shaikh SS, Kumar S. Medicine 2024). PMID 39093754. Read 2026-10-22.
- Randomized clinical trial: the effect of probiotic Bacillus coagulans Unique IS2 vs. placebo on the symptoms management of irritable bowel syndrome in adults (Madempudi RS et al. Sci Rep 2019). PMID 31434935. Read 2026-10-22.
- The Efficacy and Safety of Single-Strain Probiotic Formulations Containing Bifidobacterium lactis or Bacillus coagulans in Adult Patients with Irritable Bowel Syndrome (Skrzydło-Radomańska B et al. J Clin Med 2023). PMID 37510953. Read 2026-10-22.
- World Gastroenterology Organisation. WGO Global Guideline: Probiotics and prebiotics, 2023 PDF edition, Tables 7 to 9. February 2023. Read 2026-10-22.
- Strain-Specific Systematic Review with Meta-Analysis of Probiotics Efficacy in the Treatment of Irritable Bowel Syndrome (J Clin Med 2026). PMID 41682832. Read 2026-10-22.
- Probiotics and synbiotics in chronic constipation in adults: A systematic review and meta-analysis of randomized controlled trials (van der Schoot A et al. Clin Nutr 2022). PMID 36372047. Read 2026-10-22.
- Efficacy and safety of spore-forming probiotics in the treatment of functional dyspepsia: a pilot randomised, double-blind, placebo-controlled trial (Wauters L et al. Lancet Gastroenterol Hepatol 2021). PMID 34358486. Read 2026-10-22.
- The probiotic Bacillus subtilis BS50 decreases gastrointestinal symptoms in healthy adults: a randomized, double-blind, placebo-controlled trial (Garvey SM et al. Gut Microbes 2022). PMID 36269141. Read 2026-10-22.
- Bacillus clausii for the Treatment of Acute Diarrhea in Children: A Systematic Review and Meta-Analysis (Ianiro G et al. Nutrients 2018). PMID 30103531. Read 2026-10-22.
- Effectiveness of Bacillus clausii in the Prevention of Antibiotic-Associated Diarrhea and Gastrointestinal Symptoms: A Systematic Review (Abreu AT et al. Antibiotics 2025). PMID 40426506. Read 2026-10-22.
- Bacillus spore-forming probiotics: benefits with concerns? (Todorov SD et al. Crit Rev Microbiol 2022). PMID 34620036. Read 2026-10-22.
- Bacillus As Potential Probiotics: Status, Concerns, and Future Perspectives (Elshaghabee FMF et al. Front Microbiol 2017). PMID 28848511. Read 2026-10-22.
- NCCIH (US National Center for Complementary and Integrative Health). Probiotics: Usefulness and Safety. Read 2026-10-22.
- Emerging issues in probiotic safety: 2023 perspectives (Merenstein D et al. Gut Microbes 2023). PMID 36919522. Read 2026-10-22.
- NHS (UK). Diarrhoea and vomiting. Read 2026-10-23.