Best Herbs and Supplements for Constipation: Magnesium, Fibre and Senna Ranked by Evidence
The supplements with the best evidence for constipation are magnesium (as citrate or oxide), psyllium husk and senna, in that order of how most people should try them, followed by the probiotic Bifidobacterium lactis and partially hydrolysed guar gum for people who bloat on ordinary fibre. Magnesium is first because it works within 6–12 hours, has placebo-controlled trials showing about 70% response, and is cheap; the form you buy decides whether it does anything, which this guide spells out. Senna works fastest but is for short runs; fibre is the long-term fix.
This page is for adults passing fewer than three stools a week, straining, producing hard pellets (Bristol types 1–2), or feeling they never fully empty, including constipation from travel, pregnancy or opioid painkillers. See a doctor first if there is blood in the stool, unexplained weight loss, severe or worsening abdominal pain, vomiting, inability to pass gas, anaemia, a new change in bowel habit after 50, or a family history of bowel cancer. An underactive thyroid, high calcium, diabetes and a long list of medicines (opioids, iron, calcium tablets, calcium-channel blockers, anticholinergics, antidepressants, ondansetron) cause constipation that no laxative fixes properly.
One caveat before the list. 'Natural' does not mean gentle: senna is a drug by any definition, and fibre makes slow-transit constipation worse if fluid is low. Most people with ordinary constipation do best combining an osmotic (magnesium) with a bulk fibre, and keeping a stimulant for rescue.
Quick answer
- Magnesium citrate or oxide — 70% of chronic constipation patients responded to 1.5 g/day magnesium oxide in a 28-day RCT versus 25% on placebo; works overnight
- Psyllium husk — the guideline-recommended fibre; 10 g/day increases stool frequency and softens stools, better than docusate head to head
- Senna — a stimulant laxative that produces a bowel movement in 6–12 hours; matched magnesium oxide in a 2021 three-arm RCT
- Bifidobacterium lactis — probiotics added 1.3 bowel movements a week and cut transit time by 12 hours in a meta-analysis of 14 RCTs
- Partially hydrolysed guar gum — 5 g/day improved frequency and straining without the gas of psyllium or inulin
- Inulin — 12 g/day took stool frequency from 3.6 to 4.9 per week in a 4-week RCT
The 8 best herbs and supplements for constipation
Ranked by the strength of human evidence. Strong = multiple trials or a meta-analysis. Moderate = a few small trials. Preliminary = early or animal data.
Magnesium (citrate or oxide)
Strong evidenceMagnesium salts hold water in the colon, softening stool and triggering a bowel movement in 6–12 hours. In a 2019 double-blind RCT of about 60 Japanese adults with chronic constipation, 1.5 g/day of magnesium oxide for 28 days produced an overall response in 70.6% versus 25% on placebo and improved stool form and quality of life, and a 2021 three-arm trial of 90 adults found the same dose matched senna and beat placebo for complete spontaneous bowel movements. Trials of magnesium-sulphate-rich mineral water (about 1 L/day) in 244 women found higher response rates within 2 weeks. Which form matters: citrate and oxide are poorly absorbed, so they stay in the gut and pull water in; glycinate is well absorbed and the least laxative; threonate does nothing for the bowel.
- Key evidence
- 2019 RCT of magnesium oxide (Mori, J Neurogastroenterol Motil) and 2021 senna vs magnesium oxide vs placebo RCT of 90 adults (Morishita, Am J Gastroenterol)
- Studied dose
- Magnesium citrate 200–400 mg elemental at bedtime (check the label for elemental magnesium, not salt weight); or magnesium oxide 500–1,500 mg/day (the trial dose of 1.5 g is about 900 mg elemental); titrate every 3 days to one soft daily stool
- Best for
- Hard, infrequent stools in otherwise healthy adults, travel constipation, and people who hate fibre
- Cautions
- Do not use with kidney disease (eGFR under 30): magnesium accumulates and can cause weakness, low blood pressure and heart rhythm problems. Separate from levothyroxine, quinolone and tetracycline antibiotics, bisphosphonates and iron by 2–4 hours. Cramping and watery stools mean too much; reduce by 100 mg. Generally regarded as safe in pregnancy as a food-based fibre, though trial data in pregnancy are limited. at ordinary doses.
Psyllium is the fibre in guidelines because it holds water without being fermented, so it bulks and softens stool with little gas. In a 170-patient RCT, 5.1 g twice daily for 2 weeks raised stool water content, weight and frequency more than docusate sodium, and a 2016 systematic review of 7 RCTs found soluble fibre increased bowel movements by about 1.5 a week with better consistency, while bran did not. The American College of Gastroenterology and the 2023 AGA guideline both recommend it. It takes 2–3 days to work and is a daily habit, not a rescue.
- Key evidence
- 1998 RCT of psyllium vs docusate in 170 patients (McRorie, Aliment Pharmacol Ther) and 2016 systematic review (Christodoulides)
- Studied dose
- 5 g (one teaspoon) in 250 mL water once daily, rising to 10 g/day over 2 weeks, each dose followed by another glass of water
- Best for
- Long-term regularity, IBS-C, and anyone eating under 20 g of fibre a day
- Cautions
- Never take dry or with too little fluid: oesophageal and bowel obstruction are documented. Can worsen bloating and constipation in slow-transit constipation or if fluid intake is low. Space from levothyroxine, digoxin, lithium, carbamazepine and iron by 2 hours.
Sennosides are converted by gut bacteria into rhein anthrone, which stimulates colonic contractions and reduces water absorption, producing a bowel movement in 6–12 hours. In a 2021 placebo-controlled RCT of 90 adults with chronic constipation, senna 1 g/day (about 12 mg sennosides) for 28 days increased complete spontaneous bowel movements as much as magnesium oxide did, with both far ahead of placebo, and senna is the standard comparator in opioid-induced constipation trials. Long-term tolerance in humans is less common than feared, but it is still best used for runs of days, not months, unless a doctor agrees.
- Key evidence
- 2021 RCT of 90 adults: senna vs magnesium oxide vs placebo (Morishita, Am J Gastroenterol)
- Studied dose
- 15–30 mg sennosides (one to two 8.6 mg tablets, or 1 g of leaf as tea) at bedtime, for up to 7 days without medical advice
- Best for
- Rescue after 3 days without a bowel movement, opioid constipation, and pre-travel
- Cautions
- Causes cramping; pairing it with fibre or magnesium reduces the dose needed. Avoid with bowel obstruction, severe abdominal pain or an inflammatory bowel flare. Daily use for weeks can cause low potassium, which is dangerous with digoxin and diuretics. Melanosis coli (brown colon pigment) from long use is harmless and reversible. Acceptable in pregnancy for short courses.
Bifidobacterium lactis (probiotic)
Moderate evidenceA 2014 meta-analysis of 14 RCTs (1,182 patients) found probiotics increased stool frequency by 1.3 bowel movements per week and shortened gut transit time by 12.4 hours, with Bifidobacterium lactis strains (BB-12, HN019, DN-173 010) responsible for most of the effect and Lactobacillus strains adding little. A 2-week RCT of 100 adults on B. lactis HN019 found transit time fell from 49 to 21 hours at the high dose. Probiotic constipation trials are mostly industry-funded and heterogeneous, and effects are modest, which is why this sits below the laxatives despite the trial count.
- Key evidence
- 2014 meta-analysis of 14 RCTs (Dimidi, Am J Clin Nutr)
- Studied dose
- 1–10 billion CFU/day of a named B. lactis strain (BB-12, HN019 or DN-173 010), daily for at least 4 weeks
- Best for
- Mild constipation with bloating, and people who want a daily non-laxative
- Cautions
- Avoid with severe immunosuppression, short bowel syndrome or a central line. Products that list 'Bifidobacterium' without a strain code are untested. Stop if nothing changes by 8 weeks.
PHGG is a soluble fibre that ferments slowly, so it increases stool bulk and moisture with far less gas than inulin or wheat bran. A 2014 study of 40 adults with chronic constipation found 5 g/day for 4 weeks increased weekly bowel movements, shortened colonic transit and reduced straining and hard stools, and a paediatric RCT found PHGG as effective as lactulose with fewer side effects. In nursing-home residents it reduced laxative use. It also normalises stool in diarrhoea, which makes it the fibre of choice when stools alternate.
- Key evidence
- 2014 trial of 40 adults with chronic constipation (Polymeros, Dig Dis Sci)
- Studied dose
- 5–6 g/day of PHGG (Sunfiber or Benefiber) stirred into any drink, for 4–12 weeks
- Best for
- People who bloat on psyllium, mixed constipation and diarrhoea, and older adults
- Cautions
- Very few interactions and no drug binding of note. Mild gas in week one. Generally regarded as safe in pregnancy and in children at reduced doses, as a food-based fibre, though trial data in those groups are limited.
Inulin (chicory prebiotic fibre)
Moderate evidenceChicory inulin is fermented to short-chain fatty acids, which lower colonic pH and speed transit. A 2017 RCT of 44 adults with constipation found 12 g/day for 4 weeks increased stool frequency from 3.6 to 4.9 bowel movements a week and softened stools versus placebo, and a 2017 meta-analysis of 5 trials found inulin-type fructans improved frequency and consistency. The limit is gas: bloating and flatulence rise steeply above 10 g/day and people with IBS often feel worse.
- Key evidence
- 2017 RCT of 44 adults (Micka, Int J Food Sci Nutr)
- Studied dose
- 5–12 g/day of chicory inulin or oligofructose, built up from 3 g over 2 weeks, with meals
- Best for
- Mild constipation in people without IBS, and anyone who also wants a bifidogenic effect
- Cautions
- A high-FODMAP fibre: can worsen bloating, SIBO and IBS. No drug interactions. Generally regarded as safe in pregnancy as a food-based fibre, though trial data in pregnancy are limited.
Glucomannan from konjac root absorbs up to 50 times its weight in water and forms a viscous gel that bulks stool. A 1991 RCT of 40 adults found 1 g three times daily increased bowel frequency and improved stool form over a month, and a 2004 RCT in 31 constipated children found it improved frequency and reduced laxative use, but a larger 2011 trial of 72 children found no benefit over placebo. The adult evidence is old and thin, and the capsules themselves have caused oesophageal obstruction when swallowed with too little water.
- Key evidence
- 1991 RCT of 40 adults (Passaretti, Ital J Gastroenterol); negative 2011 paediatric RCT (Chmielewska, Clin Nutr)
- Studied dose
- 1 g three times daily (3–4 g/day) with at least 250 mL of water each dose, for 4 weeks
- Best for
- People who want a bulking fibre in capsule form and also want modest appetite reduction
- Cautions
- Must be taken with plenty of water; tablets and capsules have lodged in the oesophagus. Take oral drugs 1 hour before or 4 hours after, since it slows absorption of sulfonylureas and other medicines. Avoid with swallowing difficulty or structural bowel disease.
Triphala, the Ayurvedic blend of three fruits (amla, haritaki, bibhitaki), acts as a mild bulk and stimulant laxative through its tannins and anthraquinone-like compounds. A 2011 study of 150 adults with constipation found a triphala-based formulation improved stool frequency and consistency over 2 weeks versus baseline, and an earlier open-label study of 36 patients reported improvement in about three quarters, but there is no placebo-controlled trial of triphala alone. It is gentle and well tolerated, which makes it a reasonable traditional option once the evidence-based picks have failed, not before.
- Key evidence
- 2011 open-label study of 150 adults (Munshi); no placebo-controlled trial
- Studied dose
- 1–3 g of triphala powder in warm water at bedtime, or 500 mg capsules twice daily, for 2–4 weeks
- Best for
- People who prefer a food-like herbal blend and have mild, intermittent constipation
- Cautions
- Can cause loose stools and cramps at higher doses. Mild blood-sugar-lowering effect: caution with diabetes drugs. Heavy-metal contamination has been found in some imported Ayurvedic products, so buy third-party tested brands. Avoid in pregnancy for lack of data.
How to choose
- If you have not had a bowel movement for 2–3 days and feel uncomfortable, take magnesium citrate (300–400 mg elemental) at bedtime; if nothing happens by the next evening, add senna for 1–3 nights.
- For ongoing regularity, build fibre: psyllium 10 g/day if you tolerate it, PHGG if you bloat, inulin if you also want a prebiotic effect. Give any fibre 2 weeks and drink more water.
- Which magnesium is best for constipation: citrate for most people (predictable, well tolerated), oxide if you want the cheapest and most laxative option, hydroxide (milk of magnesia) for one-off use. Glycinate is for sleep and cramps and barely moves the bowel; threonate is for the brain and does nothing here.
- If you take opioids, fibre alone will not work and can make things worse; senna plus magnesium is the standard combination, and prescription options exist if that fails.
- If constipation alternates with diarrhoea or comes with bloating and pain, treat it as IBS-C: PHGG, psyllium and peppermint oil rather than stimulants, and consider gut-directed CBT.
- Keep a 2-week stool diary (Bristol scale and frequency) before and after any change. Constipation is defined by what your gut does, not by what the bottle promises.
What to skip
Aloe vera latex and cascara
Both are anthraquinone stimulant laxatives like senna, but the FDA removed them from over-the-counter laxatives in 2002 because manufacturers submitted no safety data; aloe latex is also linked to kidney injury and showed carcinogenic activity in rodents at high doses. Senna does the same job with decades of safety data.
'Detox' and 'slim' teas
Most are senna in disguise, sold for daily use with no dose stated. Daily stimulant laxatives for weight loss cause potassium loss, dehydration and dependence, and lose no fat because calories are absorbed before the colon.
Apple cider vinegar for constipation
No trial has tested it; the one relevant study found vinegar slowed gastric emptying in diabetics. It erodes tooth enamel at the doses recommended online.
Magnesium glycinate or threonate sold 'for constipation'
They are absorbed too well to pull water into the colon. Glycinate is a fine magnesium for sleep and cramps, but if the bowel is the target you want citrate, oxide or sulphate.
Safety and when to see a clinician
- See a clinician if constipation comes with blood in the stool, unexplained weight loss, severe or worsening abdominal pain, vomiting, inability to pass gas, anaemia, a new change in bowel habit after 50, or a family history of bowel cancer; these need investigation, not a laxative.
- Common causes a doctor will check before you buy anything: underactive thyroid, high calcium, diabetes, and medicines including opioids, iron, calcium supplements, calcium-channel blockers, anticholinergics, tricyclics, antipsychotics and ondansetron.
- Magnesium is unsafe in kidney disease (eGFR under 30) and interacts with levothyroxine, quinolone and tetracycline antibiotics, bisphosphonates and iron; space doses 2–4 hours apart.
- Stimulant laxatives (senna, and any 'detox tea') used daily for weeks cause low potassium, which is dangerous with digoxin, diuretics and in anyone with heart disease; use for up to a week without advice.
- Bulk fibres and glucomannan require 250 mL of water per dose; without it they can obstruct the oesophagus or bowel, and they are unsafe with swallowing difficulty or known strictures.
- In pregnancy, psyllium, PHGG, inulin and magnesium at normal doses are first-line; senna is acceptable short-term in the second and third trimesters; avoid aloe latex, cascara and castor oil.
What matters as much as any herb
- Kiwi fruit: two green kiwis a day increased complete spontaneous bowel movements by about 1.5 per week in a 2023 multicentre RCT of 184 people, matching psyllium with less bloating.
- Fluid: fibre without fluid is cement. In one trial, adding 1.5–2 L/day of water to a 25 g fibre diet increased bowel frequency and reduced laxative use, while fibre alone did not.
- Timing and posture: the gastrocolic reflex is strongest 20–30 minutes after breakfast; sit then, with feet on a footstool so hips are above knees, and do not strain for more than a minute.
- Movement: a 12-week programme of daily walking shortened colonic transit time in sedentary adults with chronic constipation.
- Pelvic floor: if you strain despite soft stool, up to a third of chronic constipation is dyssynergic defecation, and biofeedback therapy succeeds in about 70% of cases where laxatives fail.
Frequently asked questions
Which magnesium is best for constipation?
Magnesium citrate for most people: it is poorly absorbed, so it stays in the gut and draws water in, and it is gentler than oxide. Magnesium oxide is the cheapest and most laxative and was the form used in the Japanese trials at 1.5 g/day. Glycinate and threonate are absorbed too well to help the bowel much.
How much magnesium citrate should I take for constipation?
Start with 200–300 mg of elemental magnesium at bedtime and increase by 100 mg every 3 days until you get one soft stool a day, usually at 300–400 mg. The 10-ounce bottles of liquid magnesium citrate sold in pharmacies are a bowel-prep dose, not a daily remedy. Anyone with kidney disease should not use magnesium laxatives at all.
What is the fastest natural remedy for constipation?
Senna at bedtime works in 6–12 hours; magnesium citrate typically works overnight. A glycerin suppository works in 15–60 minutes if you need something immediate. Kiwi fruit, fibre and probiotics take days to weeks and are for prevention rather than rescue.
Is it safe to take magnesium for constipation every day?
With normal kidney function, yes: daily magnesium oxide is routine long-term therapy in Japan, and the AGA guideline lists it as an option. Keep to the lowest dose that produces a soft daily stool, get kidney function checked if you are over 65 or on blood-pressure medication, and take it 2–4 hours away from thyroid medication and antibiotics.
Does fibre make constipation worse?
It can. Insoluble fibre such as wheat bran, and any fibre taken without enough fluid, bulks stool that the colon is already struggling to move. A 2012 study found some patients with chronic constipation improved when they stopped fibre altogether. Psyllium and PHGG are the exceptions because they hold water; if those fail, the problem is transit or pelvic floor, not fibre intake.
What herbs help with constipation?
Senna is the herb with the strongest evidence and is a licensed medicine. Triphala has open-label studies, and ground flaxseed (10 g twice daily) beat psyllium in one 2018 trial of diabetics with constipation. Aloe latex and cascara work the same way as senna but lost their over-the-counter status for lack of safety data. Ginger, dandelion and fennel have no constipation trials.
Can probiotics help with constipation?
Modestly. Bifidobacterium lactis strains added about 1.3 bowel movements a week and cut transit time by 12 hours in a meta-analysis of 14 trials; Lactobacillus strains did little. Give a named strain 4–8 weeks, and treat it as an add-on to fibre or magnesium rather than a laxative.
References
- Mori S, Tomita T, Fujimura K, et al.. A Randomized Double-blind Placebo-controlled Trial on the Effect of Magnesium Oxide in Patients With Chronic Constipation. Journal of Neurogastroenterology and Motility (2019)
- Morishita D, Tomita T, Mori S, et al.. Senna Versus Magnesium Oxide for the Treatment of Chronic Constipation: A Randomized, Placebo-Controlled Trial. American Journal of Gastroenterology (2021)
- Dupont C, Campagne A, Constant F. Efficacy and safety of a magnesium sulfate-rich natural mineral water for patients with functional constipation. Clinical Gastroenterology and Hepatology (2014)
- McRorie JW, Daggy BP, Morel JG, et al.. Psyllium is superior to docusate sodium for treatment of chronic constipation. Alimentary Pharmacology and Therapeutics (1998)
- Christodoulides S, Dimidi E, Fragkos KC, et al.. Systematic review with meta-analysis: effect of fibre supplementation on chronic idiopathic constipation in adults. Alimentary Pharmacology and Therapeutics (2016)
- Dimidi E, Christodoulides S, Fragkos KC, Scott SM, Whelan K. The effect of probiotics on functional constipation in adults: a systematic review and meta-analysis of randomized controlled trials. American Journal of Clinical Nutrition (2014)
- Micka A, Siepelmeyer A, Holz A, Theis S, Schön C. Effect of consumption of chicory inulin on bowel function in healthy subjects with constipation: a randomized, double-blind, placebo-controlled trial. International Journal of Food Sciences and Nutrition (2017)
- Polymeros D, Beintaris I, Gaglia A, et al.. Partially hydrolyzed guar gum accelerates colonic transit time and improves symptoms in adults with chronic constipation. Digestive Diseases and Sciences (2014)
- Chmielewska A, Horvath A, Dziechciarz P, Szajewska H. Glucomannan is not effective for the treatment of functional constipation in children: a double-blind, placebo-controlled, randomized trial. Clinical Nutrition (2011)
- Gearry R, Fukudo S, Barbara G, et al.. Consumption of 2 Green Kiwifruits Daily Improves Constipation and Abdominal Comfort: Results of an International Multicenter Randomized Controlled Trial. American Journal of Gastroenterology (2023)
- Chang L, Chey WD, Imdad A, et al.. AGA Clinical Practice Guideline on the Pharmacological Management of Chronic Idiopathic Constipation. Gastroenterology (2023)
- NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals (2022)View source
- NHS. Constipation (2023)View source
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Ask about constipationThis 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.