Strain-by-Condition Evidence Reference: Which Strains Were Tested for What (Guideline and Review Tables)
A reference table of which probiotic strains were tested for which digestive concern, from WGO, AGA, Cochrane and review sources, with source, year and strength. Not a recommendation.
Content last updated . This page has not been medically reviewed.
What this page is, and is not
Many readers search "best probiotic strain for IBS" or "which probiotic for bloating". This page does not pick winners. It lists, for each concern, the strains that named bodies or reviews report trials for, with the source and year. WGO says plainly that there is no comparative evidence to rank products by efficacy. [1] The AGA found that the effect of one strain cannot be assumed for all probiotics. [2] ESPGHAN's 2023 position paper made recommendations only when at least two trials existed on a similar, well-defined strain, and said probiotics with no documented benefit should be discouraged. [3]Three cautions before reading the table:
- WGO's tables list positive trials only. Null trials were not included and trial bias was not assessed. [4] A strain listed there had at least one favorable trial, not a guaranteed result.
- "Level" is WGO's evidence level. Level 1 is a systematic review of randomized trials, level 2 consistent randomized trials without a systematic review, level 3 a single randomized trial. [4] "CoE" is the AGA's certainty of evidence.
- Amounts in the sources are trial amounts. We omit them here. They are study amounts, never advice.
Evidence labels used in the last column: promising but limited, mixed, insufficient evidence, no good evidence of benefit. They are our plain summaries.
Strain-by-concern reference
| Concern and population | Strains or products named in the source | What the source says | Source and year | Label |
|---|---|---|---|---|
| Preventing antibiotic-associated diarrhea, adults | S. boulardii CNCM I-745 and Lacticaseibacillus rhamnosus GG (level 1); L. acidophilus CL1285 with L. casei LBC80R (level 2) | Listed for prevention in hospital and outpatient settings. [4] | WGO 2023 | Promising but limited |
| Preventing antibiotic-associated diarrhea, children | S. boulardii and L. rhamnosus GG (level 1; ESPGHAN 2016 and 2022 cited) | Cochrane pooled all probiotics: diarrhea in 8% vs 19% (RR 0.45, moderate certainty). [4][5] | WGO 2023; Cochrane 2019 | Promising but limited |
| Preventing C. difficile-associated diarrhea | S. boulardii CNCM I-745 and L. acidophilus CL1285 with L. casei LBC80R (level 2) | AGA: low CoE for these formulations. [4][2] Cochrane 2025, all probiotics: RR 0.50, low certainty; about 65 people treated per case prevented; benefit seen in people not immunocompromised. [6] | WGO 2023; AGA 2020; Cochrane 2025 | Promising but limited |
| Acute infectious diarrhea, children | L. rhamnosus GG, S. boulardii, L. reuteri DSM 17938, L. rhamnosus 19070-2 with L. reuteri DSM 12246 (level 1; ESPGHAN 2022 cited) | AGA found no US or Canadian trial reporting benefit for a probiotic here, so applicability is very uncertain. [4][2] | WGO 2023; AGA 2020 | Mixed |
| Added to H. pylori treatment | Adults: L. rhamnosus GG, S. boulardii CNCM I-745, B. clausii named strains (level 2) | Fewer treatment side effects or higher eradication; the guideline cites weak-quality evidence and none for a probiotic alone. [4][1] | WGO 2023 | Promising but limited |
| IBS, adults | B. bifidum MIMBb75, L. plantarum 299v, B. longum 35624 (formerly B. infantis) (level 2); B. coagulans MTCC 5856, S. cerevisiae CNCM I-3856 (level 3) | AGA: individual trials had low or very low CoE; S. boulardii showed no pain difference. [4][2] A 2026 meta-analysis found efficacy for B. longum 35624, L. rhamnosus GG, L. plantarum 299v, S. cerevisiae CNCM I-3856 and B. coagulans Unique IS2; efficacy not demonstrated for E. coli Nissle 1917, L. gasseri BNR17 or L. casei Shirota; S. boulardii conflicting. [7] | WGO 2023; AGA 2020; review 2026 | Mixed |
| Functional abdominal pain or IBS, children | L. reuteri DSM 17938 and L. rhamnosus GG (level 1; ESPGHAN 2022 cited) | No firm evidence for probiotics as a group. [4] | WGO 2023 | Mixed |
| Chronic constipation, adults | B. lactis (as a group); L. reuteri DSM 17938 (level 2); B. animalis subsp. lactis HN019 (level 3) | A 2022 review: probiotics helped response (57% vs 44%); B. lactis helped stool frequency, but mixtures, B. coagulans Unique IS2 and L. casei Shirota did not. [8][4] | Review 2022; WGO 2023 | Promising but limited |
| Constipation, children | None identified | NCCIH: one 2017 review found no helpful probiotic; another saw more stool frequency, mainly in Asian children. [9] | NCCIH | Insufficient evidence |
| Bloating and gas | No bloating-only row in WGO's tables | WGO reports reduced bloating and gas as a consistent finding in IBS studies. [1] One healthy-adult trial of B. subtilis BS50 improved a bloating-burping-gas score. [10] | WGO 2023; trial 2022 | Mixed |
| Ulcerative colitis, Crohn's, pouchitis | Pouchitis: an 8-strain mixture (level 2); UC: E. coli Nissle 1917 (level 2, maintenance) | AGA: adding a probiotic does not appear to improve overall remission in mild-to-moderate UC; no evidence of benefit in Crohn's. [4][2][1] | WGO 2023; AGA 2020 | Mixed |
| Infant colic | L. reuteri DSM 17938 (level 1, breastfed infants); B. animalis subsp. lactis Bb12 (level 2) | WGO table lists reduced crying time; role in formula-fed infants less clear. [4] | WGO 2023 | Promising but limited |
| Adults in intensive care | None | WGO: insufficient evidence for probiotics or synbiotics. [1] | WGO 2023 | Insufficient evidence |
Preterm infants are not in the table on purpose. Probiotic decisions there belong to the neonatal team: NCCIH reports FDA's 2023 warning of severe infections, and WGO's table shows AGA and ESPGHAN disagreeing on some strains. [9][4] See preterm infants.
How to use the table safely
- Match the full strain code on a product to the table; a species name alone is not enough. See strain specificity and reading a label.
- A strain listed for one concern says nothing about another. McFarland's 2018 review of 228 trials found efficacy was both strain-specific and disease-specific. [11]
- Condition pages: IBS, constipation, bloating.
Frequently asked questions
What is the best probiotic strain for IBS?
No source ranks them. WGO lists several strains with favorable trials, the AGA graded individual trials low or very low certainty, and a 2026 review reported conflicting or negative results for some strains. [1][2][7]
Which probiotic is best for diarrhea?
It depends on the cause and age. Named strains are listed for antibiotic-associated and children's diarrhea, but the AGA found no North American trial showing benefit in children's gastroenteritis. [2]
Which probiotic helps constipation or bloating?
For adult constipation a 2022 review found an effect for B. lactis but not for mixtures. Bloating has no separate strain row in WGO's tables. [8][4]
Why do guidelines and trials disagree?
Strains, doses, populations and outcomes differ, and reviews that pool strains can mislead. [11]
Does a strain in this table mean a product is proven?
No. It means at least one trial (WGO) or a graded review (AGA) exists for that exact strain, not for products sold under the same species name. [4]
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 and who should ask first
The NHS says probiotics appear safe for most people, but that people with an existing condition or weakened immune system should talk to a doctor first. [12] NCCIH adds that risk is greater in severe illness and that products may contain unlisted organisms. [9] Medicines, pregnancy, kidney or liver disease and surgery are not covered strain by strain in these sources; ask a clinician or pharmacist, and see medication interactions. Bloody diarrhea, diarrhea over 7 days, dehydration signs or a sick infant need medical care first. [13] Treatment of C. difficile, IBD and H. pylori is clinician-led; do not stop or replace a prescribed medicine.
References
- World Gastroenterology Organisation. WGO Global Guideline: Probiotics and prebiotics. February 2023. Read 2026-10-22.
- Preidis GA et al. AGA Technical Review on the Role of Probiotics in the Management of Gastrointestinal Disorders. Gastroenterology 2020 (full text read via PMC8018518). PMID 32531292. Read 2026-10-22.
- Probiotics for the Management of Pediatric Gastrointestinal Disorders: Position Paper of the ESPGHAN Special Interest Group on Gut Microbiota and Modifications (Szajewska H et al. J Pediatr Gastroenterol Nutr 2023). Abstract read; full text not available.. PMID 36219218. 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.
- Probiotics for the prevention of pediatric antibiotic-associated diarrhea (Cochrane review; Guo Q et al. 2019). PMID 31039287. Read 2026-10-22.
- Probiotics for the prevention of Clostridioides difficile-associated diarrhea in adults and children (Cochrane review; Esmaeilinezhad Z et al. 2025). PMID 40931979. 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.
- NCCIH (US National Center for Complementary and Integrative Health). Probiotics: Usefulness and Safety. 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.
- Strain-Specificity and Disease-Specificity of Probiotic Efficacy: A Systematic Review and Meta-Analysis (McFarland LV, Evans CT, Goldstein EJC. Front Med 2018). PMID 29868585. Read 2026-10-22.
- NHS (UK). Probiotics. Page last reviewed 24 November 2022. Read 2026-10-22.
- NHS (UK). Diarrhoea and vomiting. Read 2026-10-23.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.