Probiotics for Constipation: What the Research Shows, Strain by Strain

Probiotics for constipation have modest, uneven evidence. Pooled trials suggest some probiotics add roughly one bowel movement a week and speed gut transit, with the most consistent results for Bifidobacterium lactis. Many other strains show no clear effect, and study quality is low. The 2025 British Dietetic Association (BDA) guideline gives probiotics only a qualified recommendation, noting it is unclear which strains work. Fiber, fluids and proven laxatives have stronger support, and constipation with warning signs needs a clinician.

Peptide Labs sells some of the products described below. This article is general information, not medical advice.

What counts as constipation

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) defines constipation as fewer than three bowel movements a week, or stools that are hard, dry or lumpy and hard to pass. About 16 in 100 US adults have symptoms, rising to about 33 in 100 adults aged 60 and older. Common causes include low fiber, too little fluid, inactivity, travel, pregnancy and medicines such as iron, opioid pain relievers, some antidepressants and aluminum or calcium antacids. Checking those causes comes before any supplement.

Do probiotics help with constipation? What the reviews found

Three meta-analyses and one guideline frame the evidence. They mostly studied adults with functional or chronic constipation, not occasional constipation.

The reviews disagree on details. The 2020 review found multi-species products helped while B. lactis alone fell short of significance; the 2022 review found the reverse. The BDA guideline, from the same research group, says B. lactis increases stool frequency (moderate evidence) but that probiotics overall do not change stool consistency or most individual symptoms. The National Center for Complementary and Integrative Health (NCCIH) also cites a 2017 review of nine studies in older adults that found a small but meaningful benefit, mainly with Bifidobacterium longum.

Why the strain on the label matters

NCCIH puts it plainly: different types of probiotics may have different effects, and a result for one strain does not carry over to another. In the reviews, Lactobacillus casei Shirota did not improve stool frequency, and several multi-strain products did not either. Trials of B. lactis used specific strains, so a label that lists only the species gives you less to go on. Our guide to choosing a probiotic explains how to read genus, species and strain codes.

Spore-forming probiotic strains

Spore-forming probiotics have their own small evidence base. In a 2020 Indian trial, 100 adults with functional constipation took B. coagulans Unique IS2 or a placebo for 4 weeks; more people in the probiotic group reached normal stool consistency (98% vs 74%), with less straining and pain. The lead authors worked for the strain’s maker. The 2022 review found no significant effect of that strain on stool frequency, and the BDA credits it only with easing incomplete evacuation and pain. A 2025 trial of the GBI-30, 6086 strain in 111 healthy adults with digestive complaints reported more frequent stools; it was co-authored by the strain’s maker. Our guide to spore-forming probiotics covers these strains in more depth.

Prebiotic fiber and probiotic-fiber combinations

Prebiotics are fibers that gut bacteria ferment. In a 2017 crossover trial of 44 adults with constipation, chicory inulin raised median stool frequency from 3 to 4 a week compared with placebo over 4 weeks and softened stools; researchers from the inulin supplier co-authored it. Products that combine probiotics with prebiotic fiber have weaker support: the 2022 review and the BDA guideline found no effect on stool frequency or symptoms. A 2024 network meta-analysis did find more weekly stools with combinations that included lactulose, a laxative, at moderate to very low certainty. For the terms, see prebiotics vs probiotics and our inulin guide.

Probiotics for constipation vs fiber and laxatives

The American Gastroenterological Association (AGA) 2020 probiotic guideline covered eight conditions, and constipation was not one of them. The 2023 AGA and American College of Gastroenterology guideline on chronic constipation did not assess probiotics at all. It strongly recommended polyethylene glycol (PEG) and conditionally recommended fiber, senna and magnesium oxide. The BDA made strong recommendations for psyllium and magnesium oxide, a stronger rating than it gave probiotics.

Many of these are over-the-counter drugs with Drug Facts labels. Metamucil psyllium powder, for example, is labeled as a fiber laxative for occasional constipation, and its label says to stop and ask a doctor if constipation lasts more than 7 days. Probiotic supplements carry Supplement Facts and may only use structure/function wording such as supporting regularity. Our fiber for constipation guide and Metamucil vs MiraLAX comparison cover those options, and our stimulant laxative guide explains senna.

Side effects when you start

The NIH Office of Dietary Supplements says probiotics may cause gas in healthy people. The BDA found that, across constipation trials, probiotics slightly reduced how severe flatulence was but did not change bloating or abdominal pain. Fiber-based products can add gas at first. Probiotics are riskier for people who are seriously ill or have weakened immune systems, and the FDA warned in 2023 about severe infections in hospitalized preterm infants given probiotics. Read our guides on when to take probiotics and probiotics and bloating for timing and early symptoms.

Reading a probiotic label for regularity

If you want to try a probiotic for constipation, check the strain codes, the CFU count through the date on the package, added sugar or sugar alcohols, and whether the product adds fiber. Three products we carry show how different labels can be:

• Physician’s CHOICE Probiotics for Weight Management & Bloating lists six species, including B. lactis, without strain codes or a CFU count, plus inulin, acacia fiber, enzymes, green tea extract and cayenne extract.
• Metamucil Fiber Gummies with Probiotics pair 5 g of inulin and soluble corn fiber with 1 billion CFU of B. coagulans (LactoSpore) per serving. They contain no psyllium and are sweetened partly with xylitol.
• Goli Pre+Post+Probiotics gummies list Bacillus subtilis DE111, a heat-killed postbiotic and a small amount of XOS fiber, with 5 g of added sugar per serving.

We found no published constipation trials for the LactoSpore or DE111 strains, so these products should not be read as evidence-backed constipation remedies. Follow the label and ask a pharmacist if you take other medicines. You can compare more labels in our fiber and gut health category.

When constipation needs a clinician

Occasional constipation is common. See a healthcare provider, and do not rely on a supplement, if you notice:

• Blood in the stool or bleeding from the rectum.
• Unexplained weight loss, fever, vomiting, or being unable to pass gas.
• Severe or constant abdominal pain, or lower back pain.
• A sudden change in bowel habits that lasts more than 2 weeks, or constipation that does not improve with self-care.
• New bowel changes at age 45 or older, or a family history of colon or rectal cancer. The US Preventive Services Task Force recommends colorectal cancer screening from age 45 for adults at average risk.

Frequently Asked Questions

Questions about a label? Contact us or read our Buyer’s Guide. Follow the label and ask a healthcare provider before starting any supplement or OTC laxative. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

Last reviewed September 2026.

Related guides: Probiotics for Bloating and Gas: What the Strain-by-Strain Evidence Shows, Best Probiotic? How to Choose a Probiotic by Strain, CFU and Evidence, Fiber for Constipation: What the Evidence Says, How Long It Takes and Natural Laxative Foods.