Best Herbs and Supplements for Gut Health: 9 Ranked by What the Trials Found
The supplements with the best evidence for gut health are psyllium husk, Saccharomyces boulardii and Lactobacillus rhamnosus GG, followed by enteric-coated peppermint oil for irritable bowel symptoms and partially hydrolysed guar gum as a gentler fibre. Each has been tested in randomised controlled trials against placebo, and the top three appear in meta-analyses of a dozen or more trials. Most products marketed as 'gut healing' have nothing like that behind them, so this guide ranks every pick by the human evidence and gives the dose that was actually studied.
This page is for adults with bloating, irregular stools, IBS-type cramping, or a gut that has not settled after antibiotics or a stomach bug. It is not a substitute for a doctor if you have blood in the stool, unintentional weight loss, symptoms that wake you at night, new bowel changes after 50, iron-deficiency anaemia, diarrhoea lasting more than 2 weeks, or a family history of bowel cancer or inflammatory bowel disease. Those need investigation first; coeliac disease and inflammatory bowel disease are routinely missed for years in people self-treating with probiotics.
One caveat before the list. 'Gut health' is not one thing, and probiotics are strain-specific: a strain that halves antibiotic diarrhoea may do nothing for bloating, and a 50-billion-CFU blend with no strain codes has usually never been tested at all. Most trials below run 4 to 12 weeks, so judge any product on that timescale, one at a time.
Quick answer
- Psyllium husk — the soluble fibre recommended in IBS and constipation guidelines, backed by a meta-analysis of 14 RCTs
- Saccharomyces boulardii — halves the risk of antibiotic-associated diarrhoea across 21 RCTs
- Lactobacillus rhamnosus GG — cuts antibiotic diarrhoea risk by about half and shortens stomach bugs in children by a day
- Peppermint oil (enteric-coated) — more than doubles the odds of global IBS improvement in a meta-analysis of 12 RCTs
- Bifidobacterium longum 35624 — the best-studied single strain for IBS pain and bloating, at a surprisingly low dose
- Partially hydrolysed guar gum — a low-gas fibre that improves both constipation and diarrhoea-type symptoms
The 9 best herbs and supplements for gut health
Ranked by the strength of human evidence. Strong = multiple trials or a meta-analysis. Moderate = a few small trials. Preliminary = early or animal data.
A 2014 meta-analysis of 14 RCTs (906 patients) found soluble fibre, almost entirely psyllium, reduced the risk of persistent IBS symptoms (relative risk 0.86) while insoluble bran did not and sometimes made things worse. In chronic constipation, 5.1 g twice daily outperformed docusate for stool water content and frequency in a 170-patient trial, and the American College of Gastroenterology gives soluble fibre a strong recommendation. It also lowers LDL cholesterol and post-meal glucose, which no other gut supplement does.
- Key evidence
- 2014 meta-analysis of 14 RCTs (Moayyedi, Am J Gastroenterol)
- Studied dose
- 5–10 g/day of psyllium husk (one to two teaspoons) in 250 mL water, starting at 3 g and building up over 2 weeks
- Best for
- Irregular stools, IBS with mixed or constipation-type symptoms, and anyone eating under 20 g of fibre a day
- Cautions
- Take with a full glass of water and never dry; it can obstruct the oesophagus or bowel without fluid. Separate from medicines by 2 hours because it can reduce absorption of carbamazepine, lithium, digoxin and levothyroxine. Rare allergy in people with chronic occupational exposure.
Saccharomyces boulardii
Strong evidenceA 2015 meta-analysis of 21 RCTs (4,780 participants) found S. boulardii cut the risk of antibiotic-associated diarrhoea from about 17% to 8.5% (relative risk 0.47), with similar protection in children and adults. It also reduces the risk of Clostridioides difficile diarrhoea in a smaller pooled analysis and shortens acute infectious diarrhoea by about a day. Because it is a yeast, antibiotics do not kill it, which is why it is the probiotic to take alongside a course rather than after.
- Key evidence
- 2015 meta-analysis of 21 RCTs (Szajewska and Kołodziej, Aliment Pharmacol Ther)
- Studied dose
- 250–500 mg (5–10 billion CFU) twice daily, started on day one of antibiotics and continued for 1 week after
- Best for
- Preventing diarrhoea on antibiotics, traveller's diarrhoea, and H. pylori eradication side effects
- Cautions
- Fungaemia has been reported in critically ill, immunocompromised and central-line patients; do not use in those groups. Antifungal drugs (fluconazole, nystatin) inactivate it. Pregnancy safety has not been established by the cited trials; ask a clinician before use.
LGG is the most studied probiotic strain in the world. A 2015 meta-analysis of 12 RCTs (1,499 participants) found it reduced antibiotic-associated diarrhoea risk by about half (relative risk 0.49), and a separate meta-analysis of 11 RCTs (2,072 children) found it shortened acute gastroenteritis by roughly one day at doses of at least 10 billion CFU. Trials in adult IBS are inconsistent, and Cochrane reviews find no clear benefit in ulcerative colitis, so its strengths are infectious and antibiotic diarrhoea rather than chronic symptoms.
- Key evidence
- 2015 meta-analysis of 12 RCTs (Szajewska and Kołodziej, Aliment Pharmacol Ther)
- Studied dose
- 10–20 billion CFU/day, with the first dose on the same day as the antibiotic
- Best for
- Children and adults on antibiotics, and acute stomach bugs
- Cautions
- Avoid with severe immunosuppression, short bowel syndrome or a central venous catheter: bacteraemia has been reported. Take at least 2 hours apart from the antibiotic dose. Products that list only 'Lactobacillus rhamnosus' without 'GG' or 'ATCC 53103' are not the studied strain.
A 2019 meta-analysis of 12 RCTs (835 patients) found enteric-coated peppermint oil more than doubled the odds of global IBS improvement versus placebo (relative risk 2.39) and reduced abdominal pain (relative risk 1.78). The 2016 IBSREST trial of 72 adults found a 40% drop in total IBS symptom score at 4 weeks with 180 mg three times daily versus 24% on placebo. Peppermint relaxes gut smooth muscle via calcium channels and blocks pain-sensing TRPM8 receptors, which is why it works on cramping and bloating within days rather than weeks.
- Key evidence
- 2019 meta-analysis of 12 RCTs (Alammar, BMC Complement Altern Med)
- Studied dose
- 180–225 mg of enteric-coated peppermint oil, 2–3 times daily, 30–60 minutes before meals, for 2–12 weeks
- Best for
- IBS cramping and bloating, especially with diarrhoea or mixed stools rather than constipation
- Cautions
- It can worsen reflux by relaxing the lower oesophageal sphincter; skip it if heartburn is a problem, and do not open or chew the capsules. Caution with cyclosporine and with gallstones or bile-duct disease. Not for infants or young children.
Bifidobacterium longum 35624
Moderate evidenceBifidobacterium longum (subsp. longum and subsp. infantis; strains 35624, NCC3001, BB536, 1714, R0175)In a 362-woman RCT, 100 million CFU/day of this strain (then called B. infantis 35624) improved the composite IBS symptom score, abdominal pain, bloating and bowel dysfunction over 4 weeks versus placebo, while a 10-billion dose did not, a reminder that probiotic dosing is not 'more is better'. A 2018 meta-analysis of 53 probiotic trials in IBS concluded that specific Bifidobacterium strains and some multi-strain products helped overall symptoms, though with low-quality evidence and heavy heterogeneity. A different B. longum strain, NCC3001, reduced depression scores in IBS patients in a small 2017 trial.
- Key evidence
- 2006 RCT of 362 women (Whorwell, Am J Gastroenterol)
- Studied dose
- 1 × 10^8 CFU once daily for at least 4 weeks (the dose that worked; 10^10 did not)
- Best for
- IBS with pain and bloating that fibre and peppermint have not settled
- Cautions
- Generally well tolerated; mild gas in the first week is common. The same immunocompromised and central-line cautions apply to any live probiotic. If you see no change by 8 weeks, stop; probiotics that do nothing in 2 months rarely start working later.
PHGG is a soluble, fully fermentable fibre that produces less gas than inulin or wheat bran because it ferments slowly along the whole colon. A 2002 RCT of 188 IBS patients found 5 g/day PHGG improved symptoms as much as 30 g of wheat bran with far better tolerance, and a 2014 trial in chronic constipation found 5 g/day increased weekly bowel movements and reduced straining over 4 weeks. Smaller trials show it also firms stool in diarrhoea-predominant IBS and in tube-fed patients, which makes it the rare fibre that helps in both directions.
- Key evidence
- 2002 RCT of 188 IBS patients (Parisi, Dig Dis Sci)
- Studied dose
- 5–6 g/day of PHGG (Sunfiber or Benefiber-type powder) dissolved in any liquid, for 4–12 weeks
- Best for
- People who bloat on psyllium or inulin, and mixed-type IBS
- Cautions
- Very few interactions; it does not bind drugs the way psyllium can. Start at half dose if you have SIBO or severe bloating. Generally regarded as safe in pregnancy as a food-based fibre, though trial data in pregnancy are limited. and for children at reduced doses.
L-glutamine
Moderate evidenceA 2019 double-blind RCT in Gut gave 5 g of glutamine three times daily for 8 weeks to 106 adults with post-infectious IBS-D and raised intestinal permeability: 79.6% reached the primary endpoint (a 50-point drop in IBS Severity Score) versus 5.8% on placebo, and permeability normalised in most of the glutamine group. That is a striking result from a single centre that has not yet been replicated, so it stays at Moderate. Glutamine is the main fuel of the cells lining the small intestine, which gives the barrier story biological plausibility.
- Key evidence
- 2019 RCT of 106 patients with post-infectious IBS-D (Zhou, Gut)
- Studied dose
- 5 g of L-glutamine powder three times daily (15 g/day) for 8 weeks; the 2–5 g/day in most 'gut health' products is untested
- Best for
- Diarrhoea-type IBS that started after a stomach infection, and a measured permeability problem
- Cautions
- Avoid with liver cirrhosis or hepatic encephalopathy (it raises ammonia), with seizure disorders, and with active cancer unless your oncologist agrees. Can interact with anti-epileptic drugs such as lacosamide.
Inulin (chicory prebiotic fibre)
Moderate evidenceInulin and oligofructose from chicory reliably raise Bifidobacterium counts within 2 weeks, shown in more than 20 RCTs. In a 2017 trial of 44 constipated adults, 12 g/day of chicory inulin for 4 weeks increased stool frequency from 3.6 to 4.9 per week and softened stools versus placebo. The downside is gas: in dose-ranging work, flatulence and bloating rise steeply above 10 g/day, and people with IBS often feel worse, not better.
- Key evidence
- 2017 RCT of 44 adults with constipation (Micka, Int J Food Sci Nutr)
- Studied dose
- 5–12 g/day of chicory inulin or oligofructose, built up from 2–3 g over 2 weeks
- Best for
- Mild constipation and anyone wanting a measured bifidogenic effect without a probiotic
- Cautions
- Can aggravate bloating, SIBO and IBS-D; this is a FODMAP. No drug interactions of note. Generally regarded as safe in pregnancy as a food-based fibre, though trial data in pregnancy are limited.
Ginger speeds gastric emptying by about 25% in healthy volunteers and in functional dyspepsia at 1.2 g, and several meta-analyses confirm it reduces nausea in pregnancy and after chemotherapy at 0.5–1.5 g/day. For the upper gut (slow stomach, nausea, early fullness after meals) it is well supported; for the lower gut it has little trial evidence, which is why it sits lower on a gut-health list than it would on a nausea list.
- Key evidence
- 2011 gastric-emptying trial in functional dyspepsia (Hu, World J Gastroenterol)
- Studied dose
- 1–1.5 g/day of dried ginger root in capsules, or 500 mg 30 minutes before meals, for 2–4 weeks
- Best for
- Nausea, slow digestion and post-meal heaviness rather than bowel symptoms
- Cautions
- Mild antiplatelet effect; use caution above 1 g/day with warfarin, apixaban or aspirin and stop a week before surgery. Can worsen reflux in some people. Doses up to 1 g/day are considered safe in pregnancy.
How to choose
- If stools are irregular or you eat little fibre, start with psyllium: it is the cheapest, best-supported intervention here and fixes both ends of the spectrum.
- If you are about to start antibiotics, take Saccharomyces boulardii or LGG from day one; taking a probiotic afterwards has much weaker evidence.
- If cramping and bloating dominate, enteric-coated peppermint oil works within days; add B. longum 35624 if pain persists after 4 weeks.
- If psyllium or inulin makes you gassy, switch to PHGG, which ferments slowly and rarely bloats.
- If diarrhoea started after a gut infection, an 8-week glutamine trial at the studied 15 g/day is reasonable; lower doses have no data.
- Pick one thing, run it for 4–8 weeks, keep a simple stool and symptom diary, then change one variable. Stacking five products at once makes it impossible to know what helped.
What to skip
Colloidal silver
Sold as an antimicrobial 'gut reset' with no human trials for any digestive condition. It accumulates in tissue and causes argyria, a permanent blue-grey skin discolouration; the FDA has ruled it unsafe and ineffective for oral use.
Apple cider vinegar
The one relevant trial found it slowed gastric emptying in type 1 diabetics with gastroparesis, the opposite of what bloating sufferers need. It erodes tooth enamel and has no demonstrated effect on the microbiome in human data.
'Leaky gut' and zonulin formulas
Serum zonulin tests are unreliable (the commercial assays largely measure other proteins), and no supplement blend has been shown to change intestinal permeability in a trial except glutamine at the 15 g/day above. Pay for one studied ingredient, not twelve unstudied ones.
Multi-strain probiotics without strain codes
If the label says 'Lactobacillus acidophilus 50 billion' with no strain designation, nobody has tested that product. CFU count is not evidence; the strains above worked at 0.1–20 billion.
Safety and when to see a clinician
- See a clinician before self-treating if you have blood in the stool, unexplained weight loss, pain or diarrhoea that wakes you at night, new symptoms after age 50, iron-deficiency anaemia, or a family history of bowel cancer or inflammatory bowel disease.
- Live probiotics (LGG, B. longum) and S. boulardii are not for people with severe immunosuppression, short bowel syndrome, a central venous line or in intensive care; bacteraemia and fungaemia are rare but documented.
- Psyllium and other bulk fibres can bind drugs: take levothyroxine, lithium, digoxin, carbamazepine and iron at least 2 hours apart, and always with a full glass of water.
- Peppermint oil relaxes the oesophageal sphincter and can worsen reflux; ginger has mild antiplatelet effects, so flag both if you take anticoagulants.
- Glutamine at the studied 15 g/day is contraindicated in cirrhosis, hepatic encephalopathy and seizure disorders, and should be cleared with an oncologist during cancer treatment.
- In pregnancy, psyllium, PHGG, S. boulardii, LGG and ginger up to 1 g/day are considered safe; skip high-dose peppermint oil and glutamine, which lack pregnancy data.
What matters as much as any herb
- Fibre from food, 25–38 g/day: the strongest microbiome lever in any trial is dietary fibre diversity, and most adults eat about 15 g. Thirty different plant foods a week beats any single supplement.
- Fermented foods: a 2021 Stanford trial found six daily servings of yoghurt, kefir, kimchi and sauerkraut raised microbiome diversity and lowered 19 inflammatory markers over 10 weeks, more than a high-fibre diet did.
- Alcohol and ultra-processed food: both reduce microbial diversity and raise intestinal permeability in human studies, and emulsifiers such as polysorbate 80 and carboxymethylcellulose thin the mucus layer in animal work and a small human trial.
- Sleep and stress: the gut-brain axis runs both ways. Gut-directed CBT and hypnotherapy have response rates of 50–70% in IBS, better than any supplement on this page.
- Exercise: moderate aerobic activity 3–5 times a week increases butyrate-producing bacteria and speeds colonic transit in intervention studies.
Frequently asked questions
What is the single best supplement for gut health?
For most people it is psyllium husk, because it has the broadest evidence (IBS, constipation, cholesterol, glucose), the lowest cost and the fewest risks. If your problem is specifically antibiotics or a stomach bug, Saccharomyces boulardii or LGG is the better single choice. There is no one capsule that improves every gut.
Should I take a probiotic every day?
Only with a reason and a named strain. In healthy people, trials show probiotics mostly pass through without colonising, and a 2018 Cell study found the extent of colonisation varied widely between individuals. Daily use makes sense during and after antibiotics, or for 4–8 weeks to test a specific strain against a specific symptom; if nothing changes by then, stop.
What are the best probiotics for gut health?
It depends on the job. Saccharomyces boulardii and Lactobacillus rhamnosus GG have the strongest data for preventing antibiotic-associated diarrhoea; Bifidobacterium longum 35624 for IBS pain and bloating; Bifidobacterium lactis strains for constipation. Look for the strain code (GG, 35624, HN019, BB-12) on the label, not the CFU count.
How long does it take to heal your gut?
The gut lining replaces itself every 3–5 days, so 'healing' in the structural sense is constant. Symptoms respond on a scale of 2–8 weeks in trials: peppermint within days, fibre within 2 weeks, probiotics and glutamine over 4–8 weeks. Be sceptical of anyone selling a 30-day gut-healing protocol; nobody has run that trial.
Are gut healing supplements like collagen, bone broth and zinc carnosine worth it?
Collagen and bone broth have no human gut trials at all; their amino acids are digested like any protein. Zinc carnosine has small trials in gastric ulcers and NSAID-induced stomach damage, so it has a narrow use for the stomach lining. Of the 'gut healing' ingredients, only L-glutamine has a controlled trial in IBS, at 15 g/day.
Can I take fibre and probiotics together?
Yes, and trials of the combination (synbiotics) are generally at least as good as either alone. Take the probiotic 2 hours away from any antibiotic dose, and build fibre up slowly so the extra fermentation does not cause gas. PHGG is the most comfortable fibre to pair with a probiotic.
Do herbs like slippery elm, marshmallow root and licorice help the gut?
They are mucilage-rich herbs with long traditional use and almost no controlled trials. Deglycyrrhizinated licorice (DGL) has small trials in dyspepsia, and slippery elm appears in one small IBS pilot where it improved constipation-type symptoms. They are low-risk, but the evidence is Preliminary, which is why they did not make the ranked list.
References
- Moayyedi P, Quigley EMM, Lacy BE, et al.. The effect of fiber supplementation on irritable bowel syndrome: a systematic review and meta-analysis. American Journal of Gastroenterology (2014)
- Szajewska H, Kołodziej M. Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea. Alimentary Pharmacology and Therapeutics (2015)
- Szajewska H, Kołodziej M. Systematic review with meta-analysis: Lactobacillus rhamnosus GG in the prevention of antibiotic-associated diarrhoea in children and adults. Alimentary Pharmacology and Therapeutics (2015)
- Alammar N, Wang L, Saberi B, et al.. The impact of peppermint oil on the irritable bowel syndrome: a meta-analysis of the pooled clinical data. BMC Complementary and Alternative Medicine (2019)
- Whorwell PJ, Altringer L, Morel J, et al.. Efficacy of an encapsulated probiotic Bifidobacterium infantis 35624 in women with irritable bowel syndrome. American Journal of Gastroenterology (2006)
- Zhou Q, Verne ML, Fields JZ, et al.. Randomised placebo-controlled trial of dietary glutamine supplements for postinfectious irritable bowel syndrome. Gut (2019)
- Parisi GC, Zilli M, Miani MP, et al.. High-fiber diet supplementation in patients with irritable bowel syndrome: a multicenter, randomized, open trial comparison between wheat bran diet and partially hydrolyzed guar gum. Digestive Diseases and Sciences (2002)
- Ford AC, Harris LA, Lacy BE, Quigley EMM, Moayyedi P. Systematic review with meta-analysis: the efficacy of prebiotics, probiotics, synbiotics and antibiotics in irritable bowel syndrome. Alimentary Pharmacology and Therapeutics (2018)
- Wastyk HC, Fragiadakis GK, Perelman D, et al.. Gut-microbiota-targeted diets modulate human immune status. Cell (2021)
- Lacy BE, Pimentel M, Brenner DM, et al.. ACG Clinical Guideline: Management of Irritable Bowel Syndrome. American Journal of Gastroenterology (2021)
- National Center for Complementary and Integrative Health. Probiotics: What You Need To Know (2019)View source
- National Center for Complementary and Integrative Health. Peppermint Oil (2020)View source
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Ask about gut healthThis guide is educational and is not medical advice. Herbs and supplements can interact with prescription medicines and are not regulated like drugs. Talk with a clinician or pharmacist before starting anything new, especially if you are pregnant, breastfeeding, have a chronic condition, or take medication.