Do probiotics improve gut health?
Short answer
Some strains may help some symptoms.
Trials show some strains ease IBS symptoms or prevent antibiotic diarrhea; others showed no benefit. The largest IBS review rated almost all evidence low or very low certainty. Results do not carry across products.
This page says what the research shows. It does not say whether you should take probiotics.
Where the evidence stands
Each dot is one on-topic paper. Steps near the top answer the question more directly. Select a dot to see the study.
↑ Stronger evidence
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Trials in people: gut symptoms such as bloating and IBS
Trials that measured gut symptoms such as bloating, pain and irregular bowels directly.
9 -
Trials in people: other measures
Trials that measured other health or performance measures.
10 -
Trials in people: lab tests or safety
Trials that measured lab tests, side effects or safety.
0None among the papers we read.
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Population studies
Studies that followed or surveyed groups of people. They show links, not causes.
0None among the papers we read.
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Blood levels and genes
Studies that link blood levels or genes to health.
0None among the papers we read.
↓ Weaker evidence
- Points to benefit
- Mixed
- No difference
- No direction
- Points to harm
Not on the ladder: 8 reviews of many studies (shown below), 1 opinion or narrative paper. Counts are papers, not people. Some studies appear in more than one paper.
See every studyWhat we found
- A 2023 review of 82 trials with 10,332 adults with IBS found some strains helped, but certainty was low to very low in almost all analyses. Goodoory 2023
- In children taking antibiotics, diarrhea hit 8% with probiotics versus 19% in comparison groups, across 33 trials with 6352 children: less than half the risk. Guo 2019
- Effects are strain-specific: one B. longum strain eased constipation while a version lacking the abfA genes did not, so results for one product do not carry over. Zhang 2023, Sniffen 2018, Peng 2023
- Not every product works: B. lactis HN019 did not beat placebo for constipation in 229 adults, and a 52-trial review of constipated children found no probiotic benefit. Cheng 2024, Wegh 2022
What the research says
Several IBS trials lowered symptom scores
In adults with diarrhea-type IBS, L. plantarum Lpla33 changed symptom scores by -128.45 and -156.77 points at two doses, versus -58.82 with placebo (lower is better). B. longum CECT 7347 gave -173.70 versus -60.44 with placebo over 84 days. Its heat-killed form did as well.
L. acidophilus DDS-1 and B. lactis UABla-12 each eased belly pain more than placebo over six weeks. These three trials had funding or staff from ADM, Chr. Hansen and UAS Laboratories.
Studies: Martoni 2023, Srivastava 2024, Martoni 2020
Other trials found little or no gut benefit
B. lactis HN019 did not beat placebo for constipation in 229 adults: weekly complete bowel movements rose 0.80 versus 0.66. A multistrain product left IBS scores unchanged (207 vs 192 with placebo), though it raised stool Bifidobacterium.
In older adults, B. longum BB536 missed its main constipation score (P = 0.074) but improved stool frequency. An L. reuteri two-strain mix eased IBS symptoms at three weeks, but not at six. B. longum NCC3001 lowered depression scores, not IBS symptoms.
Studies: Cheng 2024, Staudacher 2017, Takeda 2023, König 2024, Pinto-Sanchez 2017
Children: diarrhea helped; constipation and belly pain unclear
Across 33 trials, probiotics cut antibiotic-linked diarrhea in children (RR 0.45, 95% CI 0.36 to 0.56, less than half the risk), and doses of 5 billion CFUs a day or more did better. An umbrella review also found less diarrhea (ES = 0.52) and shorter bouts.
The umbrella review found no change in stool frequency, and a 52-trial review of constipation treatments found no probiotic benefit. A 91-trial review of children's belly pain found only hypnotherapy and a talk therapy probably worked.
Studies: Guo 2019, Chen 2025, Wegh 2022, Sinopoulou 2025
Dose and strain change the result
B. infantis 35624 eased IBS pain and bloating only at the middle dose, 1 x 10(8) cfu; the lower and higher doses matched placebo. With L. plantarum Lpla33, the higher dose cut symptom scores more.
A network review of IBS trials ranked B. coagulans first for symptom relief, but found dose made no clear difference. Reviews stress that effects are specific to each strain and condition.
Studies: Whorwell 2006, Martoni 2023, Zhang 2022, Sniffen 2018
Gut symptoms in people with other illnesses
Trials in people with Parkinson's disease, on chemotherapy for bowel cancer, on kidney dialysis or treated for H. pylori reported fewer gut symptoms with probiotics. In Parkinson's, constipation improved in 52.2% vs 8.7% of controls. An L. reuteri trial in depression found no gut symptom change.
An ADHD trial also reported better gut symptoms. In most of these trials, gut symptoms were a side measure, and several abstracts gave no symptom numbers or strain names.
Studies: Du 2022, Huang 2023, Zhou 2024, Niu 2024, Söderberg Veibäck 2025, Levy Schwartz 2024
What reviews of many studies found
Reviews pool or sum up earlier studies. They are not on the ladder, because they repeat studies already counted there.
Pooled review (meta-analysis) · Goodoory 2023
Pooled 82 trials with 10,332 adults with IBS. Some strains helped, with moderate certainty only for Escherichia strains; most results were low or very low certainty. Side effects were not higher.
Pooled review (meta-analysis) · Wu 2024
Pooled 54 probiotic trials in adults with IBS. Probiotics improved symptoms (OR = 0.53, 95% CI, 0.48 to 0.59), mainly Bifidobacterium and Lactobacillus strains, with no serious side effects. The best strain or mix remains unclear.
Pooled review (meta-analysis) · Guo 2019
Pooled 33 trials with 6352 children taking antibiotics. Diarrhea occurred in 8% with probiotics vs 19% in control groups (RR 0.45), moderate certainty. Doses of 5 billion CFUs a day or more worked better.
Pooled review (meta-analysis) · Sinopoulou 2025
Pooled 91 trials with 7226 children with IBS or belly pain, 23 of them on probiotics (1762 children). Only hypnotherapy and a talk therapy probably worked; other treatments were not effective or too uncertain to judge.
How the research grew
The papers we read span 2006 to 2025. 12 of the 28 on-topic papers came out in 2024 to 2026. The earliest trial in people here is from 2006.
- 2005–09
- 2015–19
- 2020–24
- 2025–26
Each dot is one on-topic paper, colored by what it found. Rings mark key papers:
- 2006. Large trial: B. infantis eased IBS at one dose. Whorwell 2006
- 2019. Cochrane review: probiotics cut antibiotic diarrhea in children. Guo 2019
- 2023. Biggest IBS review: 82 trials, mostly low certainty. Goodoory 2023
- 2023. Gene cluster explains why one strain works. Zhang 2023
- 2024. Large HN019 constipation trial found no benefit. Cheng 2024
Who was studied
Who took part, and how many. The largest trial here had 362 people.
- Trials in people
- 75 people · Söderberg Veibäck 2025
75 overweight adults with depression and signs of body inflammation - People in the study, log scale1101001,000
- Points to benefit
- Mixed
- No difference
- No direction
- Points to harm
Bars use a log scale: each step is ten times more people. Reviews, animal studies and papers with no count in the abstract are not shown.
Who funds this research
7 of 19 trials have company stakes (ADM, Chr. Hansen, UAS Laboratories, BioGaia, BYHEALTH, Beingpharma, DuPont/Danisco patents), including three large positive IBS trials. 5 give no disclosure. Stake-free trials also reported benefits, so confidence was not lowered.
- Company stake 7
- No disclosure in PubMed 5
- No stake declared 7
- Lai 2023Company stake
- Srivastava 2024Company stake
- Martoni 2023Company stake
- Cheng 2024Company stake
- Laterza 2025Company stake
- Martoni 2020Company stake
- König 2024Company stake
- Du 2022No disclosure in PubMed
- Pinto-Sanchez 2017No disclosure in PubMed
- Takeda 2023No disclosure in PubMed
- Staudacher 2017No disclosure in PubMed
- Whorwell 2006No disclosure in PubMed
- Huang 2023No stake declared
- Kwon 2024No stake declared
- Zhang 2023No stake declared
- Söderberg Veibäck 2025No stake declared
- Levy Schwartz 2024No stake declared
- Zhou 2024No stake declared
- Niu 2024No stake declared
Funding rule. A stake is always shown. Confidence is lowered only when every supporting study comes from a party with a stake. "No disclosure in PubMed" means the PubMed record has no conflict-of-interest statement. It does not mean there is no conflict.
All 28 on-topic papers
Each paper shows what it tested, what it found, and who has a stake. Every paper also has its own page that explains how much it counts and how it fits. See every study as a list.
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A randomized double-blind, placebo-controlled trial to evaluate the safety and efficacy of live Bifidobacterium longum CECT 7347 (ES1) and heat-treated Bifidobacterium longum CECT 7347 (HT-ES1) in participants with diarrhea-predominant irritable bowel syndrome.
200 people · 200 adults with IBS with diarrhea
TestedTwo capsules a day of live Bifidobacterium longum CECT 7347 (ES1), or the same strain heat-killed (HT-ES1), vs placebo for 84 days
IBS symptom score fell by -173.70 [±75.60] with live ES1 and -177.60 [±79.32] with heat-treated HT-ES1, vs -60.44 [±65.5] with placebo (p < .0001 for both). Stool consistency and belly pain also improved.
Points to benefitCompany stakeAbstract onlyFunded by ADM; three authors are ADM employees but were not involved in running the study or the statistics.
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Eight-Week Supplementation With Bifidobacterium lactis HN019 and Functional Constipation: A Randomized Clinical Trial.
229 people · 229 adults aged 18 to 70 with long-term constipation
TestedBifidobacterium lactis HN019, 7.0 × 109 CFU a day at the start and 4.69 × 109 CFU a day at the end, vs placebo for 8 weeks
Weekly complete spontaneous bowel movements rose 0.80 (95% CI, 0.54-1.05) with HN019 and 0.66 (95% CI, 0.41-0.90) with placebo: no difference.
No differenceCompany stakeAbstract onlyOne author holds many patents licensed to probiotic makers, including DuPont Nutrition & Bioscience.
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Effect of Lacticaseibacillus rhamnosus IDCC 3201 on irritable bowel syndrome with constipation: a randomized, double-blind, and placebo-controlled trial.
30 people · 30 adults with IBS with constipation
TestedLacticaseibacillus rhamnosus IDCC 3201 vs placebo for 8 weeks
Bowel movement discomfort and constipation discomfort improved with the probiotic at 8 weeks. Bloating severity, bloating frequency and bowel satisfaction also improved. The abstract gives no scores.
Points to benefitNo stake declaredAbstract onlyNo competing interests declared.
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Effects of dietary fibers or probiotics on functional constipation symptoms and roles of gut microbiota: a double-blinded randomized placebo trial.
242 people · 250 adults with long-term constipation (242 finished)
TestedProbiotic mix (Bifidobacterium animalis lactis HN019 plus Lacticaseibacillus rhamnosus HN001, with added oligosaccharides) vs placebo for 4 weeks; three fiber formulas were also tested
No group-by-time difference for bowel movement frequency, Bristol stool score or straining. Stool softness score rose 0.95-1.05 in the four active groups, not in placebo (P = 0.170); 4-week change was similar to the other active groups and better than placebo.
MixedCompany stakeAbstract onlyBYHEALTH Co., LTD supplied the fiber and probiotic products.
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Randomized trial · measured the question itselfMartoni et al., 2023World journal of gastroenterology · PubMed
Efficacy and dose response of Lactiplantibacillus plantarum in diarrhea-predominant irritable bowel syndrome.
307 people · 307 adults aged 18-70 with IBS with diarrhea
TestedLactiplantibacillus plantarum Lpla33 at 1 × 109 or 1 × 1010 CFU a day vs placebo for 8 weeks
IBS symptom score fell by -128.45 ± 83.30 (1B) and -156.77 ± 99.06 (10B), vs -58.82 ± 74.75 with placebo (P < 0.001). Stool responders were 62.5% and 88.4% vs 26.3% with placebo.
Points to benefitCompany stakeAbstract onlyFunded by Chr. Hansen A/S; three authors are its employees but were not involved in running the study or the statistics.
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Randomized trial · measured the question itselfTakeda et al., 2023The American journal of gastroenterology · PubMed
Usefulness of Bifidobacterium longum BB536 in Elderly Individuals With Chronic Constipation: A Randomized Controlled Trial.
79 people · 80 older adults (average age 77.9) with long-term constipation; 79 finished
TestedBifidobacterium longum BB536, 5 × 10 10 CFU a day, vs placebo for up to 4 weeks
The main constipation score did not differ between groups (P = 0.074). Stool frequency improved more with the probiotic (P = 0.008), and failure of evacuation showed a trend (P = 0.051).
No differenceNo disclosure in PubMedAbstract onlyAuthors are members of a Juntendo University microbiota research department that funded the study; no company named.
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Randomized trial · measured the question itselfDu et al., 2022Parkinsonism & related disorders · PubMed
Probiotics for constipation and gut microbiota in Parkinson's disease.
46 people · 46 people with Parkinson's disease and constipation
TestedA probiotic supplement vs a control group for 12 weeks (strain not named in the abstract)
Complete bowel movements per week rose more with probiotics (1.09 ± 1.24 vs. 0.04 ± 0.64, P < 0.001). Constipation improved in 52.2% vs 8.7% of the control group (P = 0.001).
Points to benefitNo disclosure in PubMedAbstract onlyNo disclosure in PubMed.
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Lactobacillus acidophilus DDS-1 and Bifidobacterium lactis UABla-12 Improve Abdominal Pain Severity and Symptomology in Irritable Bowel Syndrome: Randomized Controlled Trial.
330 people · 330 adults aged 18 to 70 with IBS
TestedLactobacillus acidophilus DDS-1 or Bifidobacterium animalis lactis UABla-12, each 1 × 1010 CFU a day, vs placebo for 6 weeks
Belly pain score fell more than placebo with DDS-1 (-2.59 ± 2.07, p = 0.001) and UABla-12 (-1.56 ± 1.83, p = 0.001). IBS symptom score fell -133.4 ± 95.19 and -104.5 ± 96.08 (p < 0.001).
Points to benefitCompany stakeAbstract onlyTwo authors work for UAS Laboratories but were not involved in running the study or the statistics.
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Randomized trial · measured the question itselfWhorwell et al., 2006The American journal of gastroenterology · PubMed
Efficacy of an encapsulated probiotic Bifidobacterium infantis 35624 in women with irritable bowel syndrome.
362 people · 362 women with IBS seen in primary care
TestedBifidobacterium infantis 35624 at 1 x 10(6), 1 x 10(8) or 1 x 10(10) cfu vs placebo for 4 weeks
Only the 1 x 10(8) cfu dose beat placebo for belly pain, bloating and bowel symptoms; global relief exceeded placebo by more than 20% (p < 0.02). The 1 x 10(6) and 1 x 10(10) doses did not differ from placebo.
MixedNo disclosure in PubMedAbstract onlyNo disclosure in PubMed.
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Randomized trial · other health measuresSöderberg Veibäck et al., 2025Brain, behavior, and immunity · PubMed
Add-on probiotics for inflammatory depression - A double-blind randomized placebo-controlled trial.
75 people · 75 overweight adults with depression and signs of body inflammation
TestedLimosilactobacillus reuteri probiotic vs placebo for 8 weeks, on top of usual treatment
No effect of the probiotic vs placebo on depression scores or on other measures, including gut symptoms (all p > 0.25).
No differenceNo stake declaredAbstract onlyNo competing interests declared.
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Multistrain Probiotics Plus Vitamin D Improve Gut Barrier Function and Gut Microbiota Composition in Irritable Bowel Syndrome Without Constipation: Results from a Double-Blind, Randomized, Placebo-Controlled Trial.
35 people · 35 adults with IBS without constipation
TestedOttaBac, a multi-strain probiotic plus vitamin D (cholecalciferol), vs placebo for 12 weeks, then followed to week 16
Gut leak marker zonulin fell -19.01 vs placebo at week 16 (p = 0.0053). Stool frequency and consistency improved vs placebo. IBS symptom score (IBS-SSS) and quality of life did not differ.
MixedCompany stakeAbstract onlyFunded by Beingpharma; several authors advise or consult for Actial Farmaceutica and other drug and probiotic companies.
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Exploring the impact of probiotics on adult ADHD management through a double-blind RCT.
college students with ADHD
TestedA multi-strain probiotic vs placebo, daily for 3 months
The probiotic decreased hyperactivity, improved gut symptoms and raised school grades. No numbers in abstract.
Points to benefitNo stake declaredAbstract onlyNo competing interests declared.
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Probiotic treatment induces changes in intestinal microbiota but does not alter SCFA levels in peritoneal dialysis patients-a randomized, placebo-controlled trial.
57 people · 57 people with kidney failure on peritoneal dialysis
TestedLactobacillus paracasei N1115 with fructooligosaccharide (more than 3 × 1010 CFU per bag, two bags a day) vs placebo for 12 weeks
Probiotics changed gut bacteria mix but not diversity. Short-chain fatty acid levels did not differ between groups (P > 0.05). Gut symptoms fell, particularly dyspepsia and constipation (p < 0.05).
Points to benefitNo stake declaredAbstract onlyNo competing interests declared.
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Evaluation of efficacy and safety of Lacticaseibacillus rhamnosus LRa05 in the eradication of Helicobacter pylori: a randomized, double-blind, placebo-controlled trial.
adults with Helicobacter pylori stomach infection taking antibiotics
TestedLacticaseibacillus rhamnosus LRa05 (1 × 1010 CFU) vs placebo with antibiotic therapy for 4 weeks
Cure rate was 86.11% with the probiotic and 82.86% with placebo, not a significant difference. Symptom scores showed less belly pain, acid reflux, bloating and diarrhea.
MixedNo stake declaredAbstract onlyNo competing interests declared.
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The effects of a 6-week intervention with Limosilactobacillus reuteri ATCC PTA 6475 alone and in combination with L. reuteri DSM 17938 on gut barrier function, immune markers, and symptoms in patients with IBS-D-An exploratory RCT.
65 people · 65 adults with IBS with diarrhea
TestedLimosilactobacillus reuteri ATCC PTA 6475 alone, or with L. reuteri DSM 17938, vs placebo for 6 weeks
Gut leak markers were not significantly affected. Both probiotic groups had fewer gut symptoms at 3 weeks (dual strain total score p = 0.032, pain p = 0.028). After six weeks, no symptom differed from placebo.
No differenceCompany stakeAbstract onlyTwo authors are employed by BioGaia AB, which makes L. reuteri probiotics.
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Postoperative Probiotics Administration Attenuates Gastrointestinal Complications and Gut Microbiota Dysbiosis Caused by Chemotherapy in Colorectal Cancer Patients.
100 people · 100 people with bowel cancer who had surgery and then chemotherapy
TestedA probiotic mix (strains not named in abstract) vs placebo, from after surgery to the end of the first chemotherapy course
Probiotics reduced chemotherapy-related gut problems, mostly diarrhea (p < 0.01). They also raised gut bacteria variety and short-chain fatty acids (p < 0.0001).
Points to benefitNo stake declaredAbstract onlyNo competing interests declared.
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A key genetic factor governing arabinan utilization in the gut microbiome alleviates constipation.
Mice with constipation, plus people with long-term constipation in a trial
TestedBifidobacterium longum with the abfA gene cluster vs a strain without it, vs placebo
In the human trial, the B. longum strain with the abfA cluster, but not the strain without it, increased helpful gut metabolites and improved constipation symptoms. Mouse results were similar. No numbers in abstract.
Points to benefitNo stake declaredAbstract onlyNo competing interests declared.
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Probiotic Bifidobacterium longum NCC3001 Reduces Depression Scores and Alters Brain Activity: A Pilot Study in Patients With Irritable Bowel Syndrome.
44 people · 44 adults with IBS (diarrhea or mixed) and mild to moderate anxiety or low mood
TestedBifidobacterium longum NCC3001 daily vs placebo for 6 weeks
14 of 22 patients on the probiotic had lower depression scores vs 7 of 22 on placebo (P = .04). The probiotic had no significant effect on anxiety or IBS symptoms.
No differenceNo disclosure in PubMedAbstract onlyNo disclosure in PubMed.
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A Diet Low in FODMAPs Reduces Symptoms in Patients With Irritable Bowel Syndrome and A Probiotic Restores Bifidobacterium Species: A Randomized Controlled Trial.
104 people · 104 adults with IBS
TestedA multi-strain probiotic vs placebo, crossed with a low FODMAP diet vs a sham diet, for 4 weeks
IBS symptom score did not differ between probiotic (207 ± 98) and placebo (192 ± 93) (P = .721). Stool Bifidobacterium was higher with probiotic (9.1 rRNA genes/g) than placebo (8.8) (P = .019).
No differenceNo disclosure in PubMedAbstract onlyNo disclosure in PubMed; funded by the UK Department of Health.
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Probiotics for pediatric diarrhea and constipation: an umbrella meta-analysis.
35 studies · children
TestedProbiotics compared with control groups, pooling earlier meta-analyses on diarrhea and constipation
Probiotics cut diarrhea (ES = 0.52; 95% CI: 0.40, 0.68) and shortened it (WMD = -1.85; 95% CI: -2.83, -0.86). They did not change stool frequency (WMD = 0.22; 95% CI: -0.30, 0.74).
MixedNo stake declaredAbstract onlyNo competing interests declared; no external funding.
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Efficacy of interventions for the treatment of irritable bowel syndrome, functional abdominal pain-not otherwise specified, and abdominal migraine in children: a systematic review and network meta-analysis.
91 studies, 7,226 people · children aged 4 to 18 with IBS or long-term belly pain
TestedDiet, drug, probiotic and talk therapies compared with control; 23 trials (1762 children) were on probiotics
Only hypnotherapy (RR 4.99) and cognitive behavioural therapy (RR 1.99) probably worked. For probiotics and other treatments, evidence was not effective or too weak to conclude.
No differenceCompany stakeAbstract onlyTwo authors report fees from United Pharmaceuticals and Danone, among others, paid to the hospital.
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The Efficacy of Probiotics, Prebiotics, Synbiotics, and Fecal Microbiota Transplantation in Irritable Bowel Syndrome: A Systematic Review and Network Meta-Analysis.
54 studies · adults with IBS
TestedProbiotics (54 trials), compared with placebo; Bifidobacterium and Lactobacillus strains did best. Prebiotics, synbiotics and stool transplants were also compared.
Probiotics improved IBS symptoms (OR = 0.53, 95% CI, 0.48 to 0.59), mainly Bifidobacterium and Lactobacillus strains. No serious side effects were reported. The best strain or mix remains unclear.
Points to benefitNo stake declaredAbstract onlyNo competing interests declared.
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Efficacy of Probiotics in Irritable Bowel Syndrome: Systematic Review and Meta-analysis.
82 studies, 10,332 people · adults with irritable bowel syndrome (IBS)
TestedMany different probiotic strains and mixes, compared with placebo, across 82 trials
Some strains helped overall IBS symptoms: moderate certainty for Escherichia strains, low certainty for Lactobacillus strains. Pain and bloating benefits were low to very low certainty. Side effects were not higher with probiotics.
Points to benefitNo disclosure in PubMedAbstract onlyNo disclosure in PubMed.
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Pooled review (meta-analysis)Zhang et al., 2022Frontiers in cellular and infection microbiology · PubMed
Efficacy of Probiotics for Irritable Bowel Syndrome: A Systematic Review and Network Meta-Analysis.
43 studies, 5,531 people · adults with IBS
TestedDifferent probiotic species and mixes compared with placebo and with each other
B. coagulans ranked best for symptom relief, pain, bloating and straining scores. At 8 weeks it ranked first for pain and straining. Dose made no clear difference.
Points to benefitNo stake declaredAbstract onlyNo competing interests declared.
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Nonpharmacologic Treatment for Children with Functional Constipation: A Systematic Review and Meta-analysis.
52 studies, 4,668 people · children with long-term constipation
TestedMany non-drug treatments, including probiotics and synbiotics, compared with control
Studies showed no benefit for the use of probiotics or synbiotics. Abdominal electrical stimulation and cow's milk exclusion may be effective. Most studies had high risk of bias.
No differenceNo disclosure in PubMedAbstract onlyNo disclosure in PubMed.
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Probiotics for the prevention of pediatric antibiotic-associated diarrhea.
33 studies, 6,352 people · children aged 0 to 18 taking antibiotics
TestedProbiotics (Bacillus, Bifidobacterium, Lactobacillus, Saccharomyces and others), alone or mixed, compared with placebo, other care or nothing, for 5 days to 12 weeks
Diarrhea from antibiotics happened in 8% (259/3232) with probiotics and 19% (598/3120) with controls (RR 0.45, 95% CI 0.36 to 0.56). Doses of 5 billion CFUs a day or more worked better. No serious side effects were linked to probiotics.
Points to benefitNo stake declaredAbstract onlyAll authors declared no known competing interests.
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Choosing an appropriate probiotic product for your patient: An evidence-based practical guide.
249 studies · patients with gut conditions such as antibiotic diarrhea, child diarrhea, IBS and bowel disease
Tested22 types of probiotic products, graded by the strength of trial evidence (249 trials)
Effects depend on the strain and the condition. Several products had strong evidence for preventing antibiotic diarrhea. Two types had strong evidence for IBS. 15 of 22 types (68%) had strong-moderate evidence for at least one disease.
Points to benefitCompany stakeAbstract onlyFunded by Bio-K+, which makes a probiotic; several authors are on its advisory board or are paid lecturers.
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Opinion or narrative reviewPeng et al., 2023Frontiers in cellular and infection microbiology · PubMed
Lactobacillus reuteri in digestive system diseases: focus on clinical trials and mechanisms.
people and animals with gut diseases such as infant colic, diarrhea and constipation
TestedReview of Lactobacillus reuteri strains used for gut diseases
The authors say L. reuteri is well evidenced for infant colic and can be an add-on for diarrhea, constipation and H. pylori. Evidence for belly pain, bowel disease and cancer is mostly from animals. No numbers given.
No weight on the ladderNo stake declaredAbstract onlyNo competing interests declared.
14 papers we read and set aside as off topic
- Lewandowska-Pietruszka et al., 2023. Microbiota in Autism Spectrum Disorder: A Systematic Review. (systematic review)
- Zhao et al., 2022. Probiotics for preventing acute upper respiratory tract infections. (pooled review (meta-analysis))
- Martin et al., 2024. Metabolome-associated psychological comorbidities improvement in irritable bowel syndrome patients receiving a probiotic. (randomized trial)
- Bettocchi et al., 2025. Probiotics and Fever Duration in Children With Upper Respiratory Tract Infections: A Randomized Clinical Trial. (randomized trial)
- Gupta et al., 2024. Safety, feasibility, and impact on the gut microbiome of kefir administration in critically ill adults. (trial, not randomized)
- Silva et al., 2025. DIAGNOSIS AND TREATMENT OF SMALL INTESTINAL BACTERIAL OVERGROWTH: AN OFFICIAL POSITION PAPER FROM THE BRAZILIAN FEDERATION OF GASTROENTEROLOGY. (opinion or narrative review)
- Abu-El-Haija et al., 2018. Management of Acute Pancreatitis in the Pediatric Population: A Clinical Report From the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition Pancreas Committee. (other)
- Gupta et al., 2025. Lactiplantibacillus plantarum Moderating Effect on Autoimmune Celiac Disease Triggers. (opinion or narrative review)
- McGough et al., 2004. Role of nutritional intervention in patients treated with radiotherapy for pelvic malignancy. (systematic review)
- Campeotto et al., 2020. Functional Gastrointestinal Disorders in Outpatients Aged up to 12 Months: A French Non-Interventional Study. (population study: one-time survey)
- Dinan et al., 2012. Regulation of the stress response by the gut microbiota: implications for psychoneuroendocrinology. (opinion or narrative review)
- Seven Avuk et al., 2025. The investigation of fermented food consumption on gastrointestinal symptoms: a cross-sectional study in university students. (population study: one-time survey)
- Nayebi et al., 2022. Probiotic supplementation: A prospective approach in the treatment of COVID-19. (opinion or narrative review)
- Lynch et al., 2021. Who uses probiotics and why? A survey study conducted among general gastroenterology patients. (population study: one-time survey)
Words on this page
- Relative risk (RR)
- Compares the risk in two groups. 1 means no difference. 0.85 means 15% lower risk.
- Odds ratio (OR)
- Another way to compare two groups. 1 means no difference. Below 1 means lower odds, above 1 higher odds.
- 95% CI (confidence interval)
- The range where the true result likely lies. If the range includes no effect (1 for ratios, 0 for differences), the result is not clear.
- p-value (p =)
- How likely a result this large would be by chance if there were no real effect. Below 0.05 is usually called a clear result.
- Placebo
- A dummy pill or fake treatment, so people do not know which group they are in.
- Pooled review (meta-analysis)
- A study that combines the results of many earlier studies to get one overall answer.
- Umbrella review
- A review of many pooled reviews.
- Marker
- A lab or scan result that stands in for a health outcome. A better marker does not always mean better health.
How the short answer is set
Fixed rules turn the studies into the short answer, so the same studies always give the same answer. The rules start from GRADE, a standard system for rating evidence, in plain language.
| Confidence | What it means |
|---|---|
| High | We are confident the answer is right. |
| Moderate | The answer is probably right, but it could change. |
| Low (this page) | The answer may well change. |
| Very low | Any answer is very uncertain. |
| Not tested in people | Only cell or animal studies exist. |
Why low here
- Trials in people measured gut symptoms directly, so the rating starts high.
- Largest IBS review: only 24 of 82 trials had low risk of bias.
- Results disagree: some strains helped, while other strains and trials showed no benefit.
- Company stakes are common but not universal, so they did not lower the rating.
How this page was made
Label
- Search
- PubMed, Nov 14, 2026. Searches written by Claude Opus 5.5; papers ranked by PubMed
- First read of all 42 papers
- Claude Sonnet
- Independent second read
- Claude Haiku
- Disagreements settled by
- Claude Opus 5.5
- Page text written by
- Claude Opus 5.5
- Charts
- Drawn by code from the study records
- Source check by a person
- Not yet. Required before search engines may list this page.
- Expert review
- No
- Papers read in full
- 0 of 42; all from PubMed abstracts
- Method
- v0.2, created Nov 14, 2026
Search. We ran four PubMed searches for probiotic supplements and gut symptoms such as bloating, pain and irregular bowels: pooled and systematic reviews since 2012 (10 of 224), trials in people (22 of 508), population studies (10 of 89). The first number is how many papers we read; the second is how many PubMed found. We took the ones PubMed ranks as most relevant. See the full PubMed search. Of the 42 papers read, 28 were on topic.
Limits. Digestery reads at most about 60 papers per question, so large fields are sampled, not covered in full. Abstracts can leave out key details, such as side effects and funding.
Review queue
These items wait for a person. Search engines are asked not to list the page until the first one is done.
- OpenThe short answer is new. It waits for a source check by a person.
- OpenPinto-Sanchez 2017 and Martin 2024 report the same B. longum NCC3001 trial; Martin 2024 is a later analysis. Do not count it twice.
- OpenPinto-Sanchez 2017 has no disclosure in PubMed, but the later analysis of the same trial lists Nestle employees. Check the original's disclosure.
- OpenTakeda 2023 was funded by a Juntendo University microbiota department; no company is named. Check the department's and authors' ties to BB536's maker.
- OpenNo disclosure in PubMed for trials Whorwell 2006, Staudacher 2017, Du 2022 and review Goodoory 2023. Check full texts for funding and company ties.
- OpenScope call: trials where gut symptoms were a side measure (depression, ADHD, H. pylori, dialysis) were counted relevant. Confirm this scope.
- OpenLewandowska-Pietruszka 2023 (autism review) kept off-topic: its probiotic result mixes behavior and gut symptoms behind an unclear 66% figure. Confirm.
- OpenMixed products: Lai 2023 and Zhou 2024 probiotic arms included oligosaccharides; Laterza 2025 added vitamin D; Srivastava 2024 also tested a heat-killed strain.
- OpenIBS reviews Goodoory 2023, Wu 2024 and Zhang 2022 likely pool many of the same trials; Chen 2025 pools earlier meta-analyses.
Page history
| Date | Change | Reason |
|---|---|---|
| Nov 14, 2026 | Page created from 42 papers. | First version of the page. |
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