Ranked by evidence within the category
Gut health supplements: what the evidence says
This is the largest category, with 123 supplements for digestion, bowel habits and the microbiome: 3 are rated strong, 35 moderate and 85 limited. Psyllium husk for constipation and cholesterol, enteric-coated peppermint oil for IBS and pancreatin for diagnosed pancreatic insufficiency carry the strongest evidence. The moderate tier is dominated by probiotics, whose benefit depends on the specific strain and situation, plus fibres, laxatives and enzymes with narrow uses. The limited list includes L-glutamine, digestive enzyme blends and most cleanse and leaky-gut formulas.
Evidence last reviewed: September 2026
Strong evidence (3)
A soluble, gel-forming fiber.
One of the few supplements with genuine meta-analytic support for IBS — peppermint oil beats placebo for global symptoms and abdominal pain, with a number needed to treat around 4.
A mixture of pancreatic enzymes with solid trial evidence in diagnosed exocrine pancreatic insufficiency.
Moderate evidence (35)
Live microorganisms with strain-specific effects.
Ginger has solid evidence for nausea — pregnancy-related, postoperative and to a lesser degree motion sickness — and weak, overhyped evidence for joint pain and inflammation.
Inulin-type fructans reliably increase Bifidobacterium counts and modestly soften and speed up stool, but the downstream health claims (weight, blood sugar, immunity) are weak, and inulin makes IBS symptoms worse in many people because it is a FODMAP.
A probiotic yeast with genuinely good evidence for preventing antibiotic-associated diarrhoea and reducing the side effects of H.
The most-studied probiotic strain in the world, with decent meta-analytic support for antibiotic-associated diarrhoea — but a large, rigorous NEJM trial found it completely ineffective for acute gastroenteritis in children, which should temper expectations considerably.
L.
A zinc-carnosine chelate approved as a gastric ulcer drug in Japan since 1994, with reasonable evidence for mucosal repair and for improving H.
Artichoke leaf extract produces a small but reproducible reduction in total and LDL cholesterol, and has decent trial support for functional dyspepsia.
Senna is a genuinely effective stimulant laxative — it reliably produces a bowel movement within 6-12 hours and is a first-line option for opioid-induced constipation.
Whole licorice root containing glycyrrhizin reliably raises blood pressure and lowers potassium — this is the most robustly proven effect of the herb, and it is a harm, not a benefit.
The purified oligomeric proanthocyanidin from Croton lechleri latex is crofelemer, an FDA-approved prescription antidiarrheal — genuinely effective for a narrow indication.
The most famous probiotic species and the default filler in cheap multi-strain capsules, but almost all of its real evidence comes from a handful of specific strains (NCFM, CL1285, La-5) used in blends.
A dominant species of the adult and infant colon with genuinely interesting gut-brain data for two specific strains (NCC3001 and 1714), but the generic "B.
Now formally Lactiplantibacillus plantarum, this is one of the better-studied probiotic species, with strain 299v carrying most of the evidence for IBS bloating and iron absorption.
Reclassified into the Lacticaseibacillus genus, this species is best known from drinkable dairy strains (Shirota, DN-114001) with reasonable evidence for antibiotic-associated diarrhea and modest evidence for constipation.
Properly B.
Lactase tablets do exactly what they claim — hydrolyze lactose before your gut bacteria get to it — and breath-hydrogen studies confirm it.
Alpha-galactosidase (the enzyme in Beano-type products) breaks down the galacto-oligosaccharides in beans and cruciferous vegetables before colonic bacteria ferment them, and small randomized trials show it genuinely reduces gas.
Cascara sagrada is a genuine stimulant laxative — its anthraquinone cascarosides reliably produce a bowel movement in 6-12 hours.
A starch that escapes digestion and is fermented in the colon, where it feeds butyrate-producing bacteria.
A prebiotic fiber that reliably increases bifidobacteria in the colon.
A low-viscosity soluble fiber that is unusually well tolerated for a fermentable fiber.
A food, not really a supplement: ground flaxseed supplies viscous fiber, ALA and lignans.
Products combining a probiotic with a prebiotic.
One of the few probiotic species with a well-replicated IBS result: the MIMBb75 strain improved symptoms in two randomized trials, including a heat-inactivated version.
One of the most studied probiotic species.
A spore-forming probiotic that survives heat and shelf storage, which is its main practical advantage.
A spore probiotic used for decades in Europe and Latin America, mostly as Enterogermina.
Kid-dosed probiotic drops and powders, mostly Lactobacillus reuteri or Saccharomyces boulardii.
A fixed nine-herb liquid built around bitter candytuft, peppermint and chamomile, used for functional dyspepsia.
Almost always sold and studied combined with peppermint oil.
A seaweed fibre that forms a floating gel raft on top of stomach contents.
A Japanese Kampo formula of eight herbs, widely prescribed in Japan for functional dyspepsia.
The classic yogurt bacterium, normally paired with Streptococcus thermophilus.
A probiotic Enterococcus licensed as a medicine for diarrhoea in parts of Europe.
Limited evidence (85)
Glutamine is genuinely conditionally essential in severe catabolic illness, but in healthy people it is one of the most oversold supplements on the market.
Oregano oil is a genuinely potent antimicrobial in a petri dish and almost untested in humans — one 14-person open-label parasite study is the most-cited clinical evidence there is.
Prescription-grade pancreatic enzymes are genuinely effective for diagnosed exocrine pancreatic insufficiency, and lactase works for lactose intolerance.
Bacillus spores survive stomach acid and shelf storage far better than Lactobacillus, which is a genuine formulation advantage — but the clinical evidence is thin, dominated by small manufacturer-run trials, and does not yet justify the premium price or the 'soil-based, superior' marketing.
A genuinely interesting next-generation probiotic backed by strong mouse data and one small human proof-of-concept trial — but it has never been tested in a properly powered clinical trial, and the metabolic benefits being sold are extrapolated from 32 people over 3 months.
Deglycyrrhizinated licorice removes the compound that raises blood pressure, which makes it far safer than whole licorice — but the efficacy evidence is mostly small trials from the 1970s-80s, largely superseded by acid suppression, plus a handful of modern trials of a different, flavonoid-standardised extract.
Butyrate is unquestionably important biology — it is the primary fuel for colonocytes — but oral supplements are a weak way to deliver it, and the human trial evidence is small, short and mostly on surrogate endpoints rather than symptoms.
Activated charcoal is a genuine emergency-medicine tool for recent oral poisoning, but as a wellness supplement — detox, hangovers, bloating, tooth whitening — it has essentially no supporting evidence and a real downside: it adsorbs your medications and nutrients too.
Triphala, the classic Ayurvedic blend of amalaki, bibhitaki and haritaki, has its best (though still low-quality) evidence as a mouthwash for plaque and gingivitis, where it performs roughly like chlorhexidine.
Acacia fiber is an unusually well-tolerated prebiotic — it ferments slowly and causes less gas than inulin — but the clinical evidence behind it is thin, consisting mostly of small single-centre trials, with the popular weight and cholesterol claims resting on one or two studies.
Edible clay does adsorb certain toxins — the real evidence is for binding aflatoxin in contaminated food supplies — but there is no credible support for the 'pulls toxins and heavy metals out of your body' detox claims, and clay products have themselves been recalled for lead contamination.
Fossilized algae powder marketed for parasites, detox, cholesterol and 'silica for hair and nails'.
Fiber works, but fiber gummies mostly don't deliver enough of it: a typical serving supplies 3-5 g of chicory-root inulin against a 25-38 g daily target, and inulin is a fermentable fiber that performs worse than psyllium for constipation while causing more gas.
"Bone broth protein" powder is spray-dried hydrolyzed collagen with broth flavoring — a low-quality protein sold at a premium on gut-healing claims that have never been tested in a human trial.
Boldo is a Chilean leaf used as a digestive and "liver" tea with no controlled human efficacy trials and documented cases of hepatotoxicity — the opposite of what it is sold to do.
Gentian root is the archetypal bitter, one of the most intensely bitter substances used in food, and it does reliably stimulate salivary and gastric secretion.
Bitters tinctures — gentian, wormwood, dandelion, artichoke, angelica in alcohol — act on a real mechanism: bitter taste receptors in the mouth and gut modulate digestive secretion and gut hormones.
Brazil's best-known gastric herb (Monteverdia/Maytenus ilicifolia) has one modern randomized trial showing it is non-inferior to omeprazole for reflux dyspepsia — but that trial had no placebo arm, and commercial product adulteration is well documented.
A bitter, inulin-rich root sold for liver 'detox' and water retention with essentially no supporting human trials — the single clinical diuretic study used the leaf, not the root, in 17 people with no control group.
Vitamin U (S-methylmethionine, from cabbage juice) is not a vitamin, and its ulcer reputation rests on uncontrolled 1950s case series done before Helicobacter pylori and acid-suppressing drugs existed.
A legitimate scientific category — inanimate microbes and their components, formally defined by ISAPP in 2021 — that has been adopted by marketing far faster than the human trials have arrived.
Dried, powdered kombucha in a capsule.
A purified bovine plasma protein concentrate (SBI/BIPI) sold as a medical food for chronic diarrhea and IBS-D, marketed heavily for "leaky gut".
A traditional North American demulcent bark whose mucilage plausibly coats and soothes irritated mucosa, but which has essentially never been tested on its own in a controlled human trial.
A resin from the Chios mastic tree with one genuinely decent RCT in functional dyspepsia and a weak, much-overhyped signal against H.
Betaine hydrochloride genuinely and measurably re-acidifies the stomach — that is proven in pharmacokinetic studies of drug absorption.
Ox bile extract supplies conjugated bile salts that genuinely help emulsify fat, and bile acid replacement has real clinical evidence in severe bile-salt deficiency such as short bowel syndrome.
Papain is a real, powerful protease from papaya latex with a legitimate track record in topical wound debridement.
Candida cleanse kits treat a condition — systemic "candida overgrowth" causing fatigue, brain fog and bloating in otherwise healthy people — that failed its one proper randomized test more than three decades ago.
Parasite cleanses sell a premise — that most people in wealthy countries are unknowingly harboring worms — that surveillance data does not support, using herbs that have never been shown in a human trial to clear a confirmed parasitic infection.
A systematic review of colon cleansing for general health promotion found no credible evidence of benefit and a documented list of harms, from electrolyte disturbance and renal failure to bowel perforation and death.
The Ayurvedic fruit best known as a component of Triphala, taken for regularity and detox.
An Ayurvedic mix of black pepper, long pepper and ginger used as a digestive and as a bioenhancer.
Pippali is an Ayurvedic spice rich in piperine.
A bitter herb whose only reasonable human trial is in Crohn's disease, not parasites.
A traditional parasite-cleanse ingredient, usually paired with wormwood and clove.
Chinese rhubarb contains anthraquinones, the same stimulant laxative class found in senna.
A Chinese herb whose active compound is berberine.
Bai zhu is one of the most-used herbs in Chinese digestive formulas but is almost never tested on its own.
A common weed used as a soothing herb for coughs and the gut lining.
Chen pi is a standard Chinese digestive herb rich in citrus flavonoids.
The fat-splitting enzyme sold to make heavy meals more comfortable.
A stomach protease usually sold with betaine HCl for people who believe they have low stomach acid.
The enzyme that breaks down histamine in the gut, sold for histamine intolerance.
Enzymes sold to break down gluten after accidental exposure.
A medium-chain fat sold as an antifungal for candida overgrowth.
A cheap, widely used prebiotic that feeds bifidobacteria.
A prebiotic that raises bifidobacteria at unusually low doses, around 1–3 g per day.
A cheap, tasteless soluble fiber sold for regularity.
A gel-forming soluble fiber from apples.
A good source of fiber and ALA that gels in water.
The main sugar of human breast milk, now sold as an adult prebiotic.
A bifidobacterium typical of the infant gut, best known from the A1 and M-16V strains.
A widely sold species whose evidence is scattered across many unrelated strains and outcomes.
Marketed as a "psychobiotic", almost always as the R0052 strain paired with Bifidobacterium longum R0175.
A species native to the mouth and gut.
Sold for cholesterol and immunity, but the direct test of the cholesterol claim was negative.
Best known as a GABA-producing species, which is why it is sold for calm and sleep.
The yogurt starter culture.
A soil-derived spore probiotic, usually sold as DE111.
A spore-forming probiotic that produces butyrate in the colon, used mainly in Japan and China.
Blends built around L-glutamine plus demulcents such as slippery elm, marshmallow root, liquorice and zinc carnosine.
The fibrous outer layer of the rice grain, sold as a fibre and phytonutrient supplement.
The tannin-rich pod of Ceratonia siliqua, traditionally used to shorten diarrhoea and as a chocolate substitute.
A soil- and peat-derived mixture of organic acids sold for gut and immune support.
A culinary spice with a handful of small metabolic trials, mostly from Iran.
A carminative spice used for bloating and cramping.
Multi-herb antimicrobial formulas, usually berberine plus oregano or thyme oil.
An Ayurvedic fruit traditionally used for diarrhoea and dysentery.
Bark of Holarrhena antidysenterica, used in Ayurveda for dysentery and intestinal parasites.
A carminative Indian spice used for bloating and indigestion.
A pungent resin used as a digestive spice.
A sweet carminative seed.
An intensely bitter Himalayan herb used in Ayurveda for digestion and fever.
Seed of the sensitive plant, sold in gut-cleanse and parasite protocols because its mucilage forms a sticky gel.
Nutgrass rhizome, used in Ayurveda and Chinese medicine for bloating and diarrhoea.
A classical Ayurvedic multi-herb powder for acidity and reflux.
A homeopathic dilution of the strychnine tree, sold for indigestion and hangover.
Cocktails of E.
A starch-digesting enzyme, almost always sold inside a multi-enzyme blend.
A protein-digesting enzyme sold on its own or inside digestive-enzyme blends.
An enzyme that breaks down plant cell-wall cellulose, sold to reduce gas from vegetables.
Blends of ox bile, beet, artichoke, dandelion and taurine sold for fat digestion.
A traditional fennel, ginger and bicarbonate infant preparation for colic.
A small tuber, not a nut, eaten in Spain and West Africa and high in fiber and resistant starch.
Comparison guides for this category
Psyllium, glucomannan, inulin, oat beta-glucan or acacia?
Ground flaxseed, flaxseed oil or flax lignans?
Plain MCT oil or pure C8?
Trimethylglycine for homocysteine, or betaine HCl for stomach acid?
Deglycyrrhizinated licorice (DGL) or whole licorice root?
Partially hydrolysed guar gum or plain guar gum?
BCAAs, EAAs or L-glutamine for muscle?
A generic probiotic, LGG or S. boulardii?
Goals these supplements are ranked for
An evidence-ranked guide to gut and digestion supplements: what actually helps constipation, IBS, gas, nausea and antibiotic-related…
An evidence-ranked guide to supplements for constipation: which fibres and laxatives actually work, which fit only certain cases, and what…
An evidence-ranked guide to supplements for children: the few with real support, the ones that help only in specific situations, and what…
Our verdict
Match the product to the problem: psyllium for constipation, peppermint oil for IBS pain, and a probiotic with evidence, such as Saccharomyces boulardii, alongside antibiotics. Be sceptical of probiotic labels that name only a species without a strain, and of candida, parasite and colon cleanses, which sit in the limited tier.