Supplement analysis backed by scientific evidence · PT

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Moderate evidenceGut health

Senna

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. It is for short-term or supervised use, not for daily "detox teas," and chronic misuse causes electrolyte loss and dependence-like patterns.

What the science says

  • Relieves chronic constipation Moderate evidence

    A 2023 systematic review and meta-analysis of food and supplement interventions for chronic constipation in adults found senna among the agents improving stool frequency and consistency, though the pooled estimates rested on a small number of randomized trials. Decades of clinical use and regulatory approval as an OTC laxative back its short-term efficacy; what is weak is evidence for long-term daily use.

  • Treats and prevents opioid-induced constipation Moderate evidence

    A 2024 systematic review and meta-analysis of opioid-induced constipation in cancer patients supports stimulant laxatives including senna as standard prophylaxis alongside opioid initiation, with efficacy broadly comparable to osmotic agents such as polyethylene glycol. Palliative-care guidelines recommend starting a stimulant laxative with every opioid prescription.

  • Causes weight loss ("detox" and slimming teas) Limited evidence

    Any weight change from senna is water and stool weight, recovered within a day or two; it acts in the colon, downstream of where calories are absorbed, so it does not reduce fat mass or energy uptake. Slimming-tea use is a recognized pathway into laxative misuse and hypokalemia.

  • Bowel preparation before colonoscopy Moderate evidence

    Network meta-analyses of bowel preparation regimens find senna-containing and senna-augmented regimens achieve adequate cleansing, generally as an adjunct to polyethylene glycol rather than as a standalone. Regimen choice should follow the endoscopy unit's protocol.

Dosage & safety

Studied doseStandard adult dose is 15-30 mg of sennosides at bedtime (typically 1-2 tablets), producing a bowel movement in 6-12 hours; palliative-care regimens titrate up to about 100 mg/day of sennosides. Children's doses are weight-based and should be set by a clinician. Do not use continuously for more than 1-2 weeks without medical supervision.
SafetyExpect abdominal cramping, urgency and diarrhea; overuse causes dehydration, hypokalemia and hypomagnesaemia. Prolonged use produces melanosis coli (a benign, reversible pigmentation) and, in chronic abusers, electrolyte disturbance and possible colonic dysmotility. Rare hepatotoxicity has been reported with chronic high-dose use. Potassium loss increases digoxin toxicity risk and compounds thiazide/loop diuretics and corticosteroids. Contraindicated in bowel obstruction, ileus, acute inflammatory bowel disease, appendicitis, undiagnosed abdominal pain and severe dehydration. Avoid in pregnancy except on medical advice; small amounts enter breast milk. Regulatory note: the EU banned aloe-emodin, emodin and danthron and preparations containing them in food supplements in 2021 and restricts hydroxyanthracene derivatives generally, while senna leaf/pod preparations remain available as licensed OTC medicines in most markets with mandatory short-duration labelling.

Scientific references

Where to buy

NOW Foods, Senna Leaves, 470 mg, 100 Veg Capsules

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