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What’s the best supplement for loose stools and urgency?

Quick answer

What is the best supplement for loose stools and urgency? It depends on why the stools are loose. For diarrhea-predominant IBS, the largest trial of a finished product is Bio-Kult’s 14-strain formula (400 people, 16 weeks); single strains with IBS trials include Lactobacillus plantarum 299v, Bifidobacterium bifidum MIMBb75 and B. longum 35624, and enteric-coated peppermint oil has the most trials of all. For loose stools during or after antibiotics, Saccharomyces boulardii and L. rhamnosus GG. For IBS that began after a stomach bug, glutamine at 15 g a day has one striking trial. Psyllium helps IBS of any bowel habit; bran makes it worse.

For IBS with diarrhea, the Bio-Kult 14-strain formula has a trial in 400 people over 16 weeks; during or after antibiotics, S. boulardii or L. rhamnosus GG; for IBS that began after a stomach bug, glutamine at 15 g a day has one trial; psyllium helps IBS of any bowel habit.
Source: The randomized trials cited on the page. Chart by SuppleGut, free to reuse with a link to this page.

Loose stools and urgency have several causes with different evidence: IBS with diarrhea, a course of antibiotics, the aftermath of a gut infection, and food-driven diarrhea from lactose or other sugars. The trials below are sorted by which of those they were run in, because a probiotic that prevents antibiotic diarrhea has not been shown to calm IBS, and the reverse is also true.

How the evidence ranks

SupplementBest trialWhat it showedSuits
Bio-Kult 14-strain formulaRCT, 400 adults with IBS-D, 16 weeksPain severity down 69% vs 47%; moderate-to-severe symptoms 14% vs 48%Diarrhea-predominant IBS
Enteric-coated peppermint oilMeta-analysis, 9 RCTs, 726 IBS patientsGlobal symptoms RR 2.23; pain RR 2.14IBS with cramping and urgency
L. plantarum 299vRCT, 214 IBS patients, 4 weeksPain and frequency down; 78% rated it good or excellent vs 8%IBS, any bowel habit
B. bifidum MIMBb75 (Kijimea)RCT, 122 IBS patients, 4 weeks; heat-inactivated form, 443 patients, 8 weeksAdequate relief 47% vs 11%; responders 34% vs 19%IBS, any bowel habit
B. longum 35624 (Align)RCT, 362 women with IBS, 4 weeks108 CFU beat placebo on pain, bloating and global symptomsIBS, any bowel habit
S. boulardii (Florastor)Meta-analysis, 27 trials, 5,029 adultsAntibiotic-associated diarrhea RR 0.47Loose stools on antibiotics
L. rhamnosus GG (Culturelle)Meta-analysis, 12 trials, 1,499 peopleAAD 22.4% to 12.3%; significant in children, not adults overallAntibiotics, mainly children
L-glutamine, 5 g three times a dayRCT, 106 people with post-infectious IBS-D, 8 weeksResponders 80% vs 6%; stools 2.9 vs 5.4 a dayIBS-D that began after a gut infection
Psyllium, 10 g a dayRCT, 275 IBS patients, 12 weeksAdequate relief 57% vs 35% at one monthIBS, any bowel habit
Partially hydrolyzed guar gumOpen RCT, 188 IBS patients, 12 weeks60% success vs 40% on branIBS where bran or psyllium was not tolerated

Diarrhea-predominant IBS: the trials that named the subtype

Most probiotic trials in IBS accept any bowel habit. The one large trial that enrolled diarrhea-predominant IBS specifically tested Bio-Kult’s 14-strain formulation in 400 adults with moderate-to-severe IBS-D for 16 weeks. Abdominal pain severity fell by 69% against 47% on placebo (p<0.001), the IBS Symptom Severity Score fell by 145 points, and the share still rated moderate-to-severe dropped from 100% to 14% on the probiotic against 48% on placebo. No serious adverse events were reported. The manufacturer supplied the product and funded the trial (Ishaque et al., BMC Gastroenterology, 2018).

If the diarrhea began after a stomach infection, one trial stands apart. 106 people with post-infectious IBS-D and raised intestinal permeability took 5 g of L-glutamine three times a day or placebo for eight weeks: 79.6% on glutamine reached the primary endpoint (a 50-point fall in symptom severity) against 5.8% on placebo, daily bowel movements fell to 2.9 against 5.4, and permeability normalized. Adverse events were low and similar in both groups (Zhou et al., Gut, 2019). It is a single trial in a specific group, at a dose of 15 g a day that most glutamine labels do not suggest.

IBS of any bowel habit: single strains with a trial

Lactobacillus plantarum 299v, one capsule a day for four weeks in 214 people with IBS, reduced pain severity and daily pain frequency against placebo (p<0.05), and 78.1% rated the effect excellent or good against 8.1% on placebo (Ducrotté et al., World Journal of Gastroenterology, 2012).

Bifidobacterium bifidum MIMBb75, the Kijimea strain, was tested live in 122 people with IBS for four weeks: 47% reported adequate relief against 11% on placebo, and 57% were responders against 21% (Guglielmetti et al., Alimentary Pharmacology & Therapeutics, 2011). The heat-inactivated form was then tested in 443 people for eight weeks, with 34% reaching the combined pain-and-relief endpoint against 19% (risk ratio 1.7, p=0.0007) and no difference in adverse events; the manufacturer funded it (Andresen et al., Lancet Gastroenterology & Hepatology, 2020). Check which form the bottle contains.

Bifidobacterium longum 35624, the Align strain, beat placebo on pain, bloating and global symptoms at 108 CFU a day in 362 women with IBS of any subtype over four weeks; a higher and a lower dose did not (Whorwell et al., American Journal of Gastroenterology, 2006).

Enteric-coated peppermint oil has the most trials of any option here: nine randomized trials in 726 people with IBS, relative risk 2.23 for global improvement and 2.14 for abdominal pain, with heartburn the commonest side effect (Khanna, MacDonald & Levesque, Journal of Clinical Gastroenterology, 2014). It treats the cramping and urgency rather than stool form.

Loose stools on antibiotics

This is the best-evidenced use of any probiotic, and the two organisms are different. Saccharomyces boulardii, a yeast that antibiotics do not kill, cut antibiotic-associated diarrhea by about half across 27 randomized trials in 5,029 adults (relative risk 0.47, 95% CI 0.35 to 0.63) and was judged safe, with no serious adverse effects (McFarland, World Journal of Gastroenterology, 2010). Lactobacillus rhamnosus GG reduced antibiotic-associated diarrhea from 22.4% to 12.3% across 12 trials in 1,499 people, but the effect was significant in children and not in adults overall, apart from the four trials of people on H. pylori treatment (Szajewska & Kołodziej, Alimentary Pharmacology & Therapeutics, 2015). For an adult on antibiotics, the yeast has the stronger case. Culturelle vs Florastor sets the two side by side.

Fiber: psyllium yes, bran no

Gel-forming soluble fiber improves the consistency of loose stool as well as softening hard stool (McRorie, Nutrition Today, 2015), and the IBS trial bears that out. 275 people with IBS of any subtype took 10 g a day of psyllium, bran or placebo for 12 weeks: psyllium gave adequate relief to 57% in the first month against 35% on placebo, while bran did not beat placebo and more people on bran dropped out because their symptoms got worse (Bijkerk et al., BMJ, 2009). Partially hydrolyzed guar gum is the gentler alternative when psyllium is not tolerated: 5 g a day for 12 weeks gave a 60% success rate against 40% on bran in 188 people with IBS, in an open-label trial (Parisi et al., Digestive Diseases and Sciences, 2002).

Loose stools after particular foods

Diarrhea that follows milk is lactose; in 47 adults with confirmed lactose intolerance, lactase tablets with a lactose load improved symptoms and cut breath hydrogen by 55% (Baijal et al., JGH Open, 2020). Diarrhea that follows sugar-free sweets or large portions of fruit is a question for the food diary rather than the supplement shelf; no trial of a supplement for it was found.

Signs to stop comparing supplements and get checked

Loose stools with blood, black stools, fever, unintended weight loss, waking at night to pass stool, diarrhea that began after 50, or more than two weeks of new diarrhea need a clinician first. Diarrhea after a course of antibiotics that does not settle within days is a reason to be tested for C. difficile, not to keep trying probiotics.

Products in this catalog with the trials above

probiotic Bio-Kult Everyday Probiotics, 14 Strains A 14-strain probiotic with the strongest product-specific evidence in this catalog — a 400-patient trial on this exact formulation, at a higher dose than one capsule provides. Buy it at Amazon$0.50 a day
amino Thorne L-Glutamine Powder A single-ingredient powder aimed at the gut lining itself. Buy it at iHerb$0.74 a day
probiotic Jarrow Formulas Ideal Bowel Support L. plantarum 299v One named strain, Lactobacillus plantarum 299v, with a 214-person IBS trial behind it, at 10 billion CFU in a shelf-stable capsule. Buy it at iHerb$0.76 a day
probiotic Kijimea IBS A single-strain capsule with an actual randomized, placebo-controlled trial behind it, priced well above most probiotics in this catalog. Buy it at Amazon$1.78 a day
probiotic Align Probiotic Extra Strength A once-daily capsule built around one of the most-studied probiotic strains for IBS. Buy it at iHerb$1.69 a day
herbal IBgard Digestive Gut Health Capsules Targeted-release peppermint oil for IBS-type cramping and urgency. Buy it at Amazon$0.57 a day
probiotic Florastor Unisex Daily Probiotic A yeast probiotic built for antibiotics and travel. Buy it at Amazon$1.31 a day
probiotic NOW Foods Saccharomyces Boulardii 5 Billion CFU The same probiotic yeast species as Florastor, without a named strain, at about a fifth of the price. Buy it at iHerb$0.45 a day
probiotic Culturelle Digestive Daily Probiotic A single-strain, once-daily capsule built around one of the best-studied probiotics for travel and antibiotics. Buy it at iHerb$0.75 a day
fiber NOW Foods Psyllium Husk Powder One ingredient, nothing else, mixed into water once a day. Buy it at iHerb$0.31 a day
fiber California Gold Nutrition Prebiotic Fiber (Sunfiber PHGG) A tasteless prebiotic fiber at the exact dose used in the trial. Buy it at iHerb$0.77 a day
enzyme Lactaid Fast Act Caplets For when dairy specifically is the thing that sets you off. Buy it at Amazon$0.20 a day

Common questions

What is the best probiotic for IBS-D?

The largest trial that enrolled diarrhea-predominant IBS specifically tested Bio-Kult’s 14-strain formula: 400 adults, 16 weeks, pain severity down 69% against 47% on placebo, and the share still moderate-to-severe down to 14% against 48%. Single strains with IBS trials of any subtype include L. plantarum 299v (214 people), B. bifidum MIMBb75 (122 live, 443 heat-inactivated) and B. longum 35624 (362 women).

What is the best probiotic for diarrhea from antibiotics?

Saccharomyces boulardii for adults: across 27 randomized trials in 5,029 people it cut antibiotic-associated diarrhea by about half (relative risk 0.47). Lactobacillus rhamnosus GG reduced it from 22.4% to 12.3% across 12 trials, but the effect was significant in children and not in adults overall.

Does glutamine help IBS-D?

In one trial of 106 people whose IBS-D began after a gut infection, 5 g of glutamine three times a day for eight weeks brought 79.6% to the response threshold against 5.8% on placebo and cut daily bowel movements from 5.4 to 2.9. It is a single trial in that specific group at 15 g a day.

Does psyllium help with loose stools?

In the 275-person IBS trial, 10 g a day of psyllium gave adequate relief to 57% in the first month against 35% on placebo, across all bowel-habit subtypes. Bran did not beat placebo and made more people worse. Soluble, gel-forming fiber firms loose stool as well as softening hard stool.

Does peppermint oil help urgency?

Enteric-coated peppermint oil has nine randomized trials in 726 people with IBS, with the chance of global improvement and of pain improvement more than doubled. It acts on cramping and urgency rather than on stool form, and heartburn is its commonest side effect.

When should loose stools be checked by a doctor?

Blood or black stools, fever, unintended weight loss, waking at night to pass stool, new diarrhea after 50, or more than two weeks of new diarrhea. Diarrhea after antibiotics that does not settle within days should be tested for C. difficile.

Sources

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