Probiotics for Constipation and Regularity: Trials and Reviews
What reviews and trials found when specific probiotics were tested for constipation and regularity in adults, older adults and children, why results differ by strain, and how fiber compares.
Content last updated . This page has not been medically reviewed.
Quick answer
Some reviews of trials found that certain probiotics modestly raised how often adults with functional constipation had a bowel movement. Other reviews, and a head-to-head trial, did not agree on which bacteria worked, and the reviewers themselves warn that the studies differ a lot and are often biased. [1][2] For children, the most recent network review found no clear difference in weekly bowel movements, with low or very low certainty. [3] This page is information only. It is not advice to start, stop or change anything.
Check first: when constipation needs a clinician
The NHS (UK) lists reasons to see a GP rather than self-treat: constipation that is not getting better, regular constipation, blood in your poo, unexplained weight loss, or sudden changes in how you poo. [4] The NHS also says constipation can be a side effect of a medicine, and to speak to the GP before stopping any prescribed medicine. [4] The NIDDK (US) describes constipation as a possible symptom of another medical problem, not a disease on its own. [5] NCCIH advises not to use probiotics as a reason to postpone seeing a health care provider. [6] For everyday steps, see constipation: what helps and when to get checked.How the sources describe constipation
The NIDDK describes constipation as fewer than three bowel movements a week, or stools that are hard, dry or lumpy, but notes that only you know what is normal for you. [5] That matters for trials: "more bowel movements per week" is one outcome, and softer stools or less straining are different outcomes. Results for one do not prove the other.What the evidence labels mean
We use these labels: promising but limited (some positive trials with weak or inconsistent evidence), mixed (reviews or trials disagree), insufficient evidence, and Proper evidence not found (we looked and found nothing usable). A label applies to the product, strain and group studied, not to every probiotic.What reviews and trials found
| Question | What the source found | Label |
|---|---|---|
| Adults with functional constipation, 2014 review | 14 trials (1,182 people). Pooled results showed shorter gut transit time (about 12.4 hours) and about 1.3 more bowel movements a week, with the B. lactis subgroup significant and Lactobacillus casei Shirota not. Authors cautioned about high heterogeneity and risk of bias. [1] | Promising but limited |
| Adults with chronic constipation, 2022 review | 30 trials of probiotics. [2] About 57% responded to probiotics and 44% to control. Bifidobacterium lactis raised stool frequency, but probiotic mixtures, Bacillus coagulans Unique IS2 and L. casei Shirota did not, and stool consistency did not change. [2] | Promising but limited |
| Adults, 2020 review | 15 trials. [7] Multispecies products raised stool frequency, but B. lactis alone was not significant in this review. [7] | Mixed (differs from the two reviews above) |
| One head-to-head trial, adults | 250 adults with functional constipation, 4 weeks, comparing fiber formulas, Bifidobacterium animalis subsp. lactis HN019 plus Lacticaseibacillus rhamnosus HN001, and placebo. The time-by-group test showed no effect for bowel movement frequency, stool form or straining, although stool-form scores rose in each active group and not in placebo. Oligosaccharides were in every active group. [8] | Mixed |
| Older adults | NCCIH describes a 2017 evaluation of 9 studies (778 people) that found a small but meaningful benefit; the bacteria most often tested was B. longum. [6] | Promising but limited |
| Children | NCCIH describes 2017 reviews that disagreed and were hard to compare. [6] A 2026 network review of 15 trials (1,087 children) found no significant difference in weekly bowel movements, with very low to low certainty. [3] | Insufficient evidence |
| Healthy adults, regularity | A review of B. animalis subsp. lactis trials in healthy adults found more frequent bowel movements, but no improvement in pain or bloating. [9] This does not show a benefit in people with constipation. | Promising but limited |
What these reviews cannot tell you
The reviews group results by species (for example B. lactis), and the abstracts we read do not list strain codes, doses or products. [1] The 2014 authors said that better-powered trials are needed to find the strains, doses and duration that work. [1] The one trial above that names strains (HN019 and HN001) found no clear difference in bowel movement frequency. [8] Proper evidence not found: we searched the guideline abstracts we could read for a named strain and amount recommended for constipation. The AGA-ACG 2023 guideline on chronic constipation reviewed fiber, laxatives and prescription drugs and listed no probiotics in its abstract. [10] The British Dietetic Association 2025 guideline has 20 statements on probiotics, but its abstract does not say what they are, so we could not read them. [11] To see why one strain's result does not carry over to another, read strain specificity.How fiber compares
The AGA-ACG 2023 guideline made a conditional recommendation for fiber in chronic idiopathic constipation. [10] The NHS advises increasing fibre gradually. [4] The British Dietetic Association guideline has 15 statements on fibre supplements and 20 on probiotics; across all 59 of its statements, 12 had very low and 39 low-level evidence. [11] Apart from the 250-person trial above, we did not find a trial that tested a named probiotic against fiber. For fiber types and cautions, see psyllium and fiber supplements.Related reading
See probiotics for IBS, probiotic side effects and the Probiotics & Gut Support hub.Frequently asked questions
Do probiotics help constipation?
Some reviews found that certain probiotics modestly increased bowel movement frequency in adults, but reviews disagree on which ones, and the authors flag high bias and inconsistency. [1][2][7]
Is Bifidobacterium lactis proven for constipation?
Two reviews found a significant effect for B. lactis on stool frequency, while a 2020 review did not for B. lactis alone. [1][2][7] A 250-person trial of a B. lactis HN019 combination found no clear difference in bowel movement frequency. [8] That is mixed evidence, and it applies only to the products tested.
Are probiotics better than fiber for constipation?
We did not find a source that shows that. A guideline made a conditional recommendation for fiber. [10] In a 250-person trial, stool form improved in all four active groups, including the probiotic one, and bowel movement frequency did not differ over time. [8]
Can children take probiotics for constipation?
The most recent network review found no clear difference in weekly bowel movements in children, with low or very low certainty. [3] Ask your child's clinician first. NHS advice also says to see a doctor if constipation does not improve. [4]
When should I see a doctor about constipation?
The NHS lists blood in your poo, unexplained weight loss, constipation that is regular or not improving, and sudden bowel changes. [4] In a US emergency, call 911.
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
- Immune system or serious illness. NCCIH says the risk of harm is greater in people with severe illness or a weakened immune system. [6] The NHS says to talk to a doctor first if you have a health condition or weakened immune system. [12] See probiotic safety.
- Infants. The FDA warns that preterm infants given a probiotic are at risk of invasive, potentially fatal disease; any use in a baby is a decision for the care team. [13]
- Medicines. The sources we read for this page do not describe probiotic and medicine interactions. Check how medicine interactions work and ask a pharmacist.
- Pregnancy, breastfeeding, kidney or liver conditions, surgery. The sources we read do not give specific advice for these groups. Ask a clinician or pharmacist.
- Product quality. The NHS says we cannot always be sure a product contains enough bacteria to have an effect. [12] NCCIH notes some products contain organisms other than those on the label. [6] See quality testing and certifications.
References
- Dimidi E, et al. The effect of probiotics on functional constipation in adults: a systematic review and meta-analysis of randomized controlled trials. Am J Clin Nutr. 2014;100(4):1075-84. Abstract read 2026-10-23.
- van der Schoot A, et al. Probiotics and synbiotics in chronic constipation in adults: a systematic review and meta-analysis of randomized controlled trials. Clin Nutr. 2022;41(12):2759-77. Abstract read 2026-10-23.
- Liang C, et al. Efficacy and safety of probiotics, prebiotics and synbiotics for the treatment of functional constipation in children: systematic review and network meta-analysis. Probiotics Antimicrob Proteins. 2026;18(5):6607-19. Abstract read 2026-10-23.
- NHS (UK). Constipation. Page last reviewed 26 October 2023. Read 2026-10-23.
- NIDDK (US). Definition & Facts for Constipation. Read 2026-10-23.
- NCCIH (US National Center for Complementary and Integrative Health). Probiotics: Usefulness and Safety. Read 2026-10-23.
- Zhang C, et al. Meta-analysis of randomized controlled trials of the effects of probiotics on functional constipation in adults. Clin Nutr. 2020;39(10):2960-69. Abstract read 2026-10-23.
- Lai H, et al. Effects of dietary fibers or probiotics on functional constipation symptoms and roles of gut microbiota: a double-blinded randomized placebo trial. Gut Microbes. 2023;15(1):2197837. Abstract read 2026-10-23.
- Araujo MM, et al. Effects of Bifidobacterium animalis subspecies lactis supplementation on gastrointestinal symptoms: systematic review with meta-analysis. Nutr Rev. 2022;80(6):1619-33. Abstract read 2026-10-23.
- Chang L, et al. AGA-ACG Clinical Practice Guideline: Pharmacological Management of Chronic Idiopathic Constipation. Gastroenterology. 2023;164(7):1086-1106. Abstract read 2026-10-23.
- Dimidi E, et al. British Dietetic Association Guidelines for the Dietary Management of Chronic Constipation in Adults. J Hum Nutr Diet. 2025;38(5):e70133. Abstract read 2026-10-23.
- NHS (UK). Probiotics. Page last reviewed 24 November 2022 (next review was listed as November 2025). Read 2026-10-23.
- US Food and Drug Administration. FDA Raises Concerns About Probiotic Products Sold for Use in Hospitalized Preterm Infants. News release, 26 October 2023. 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.