Berberine

Berberine is a bitter yellow alkaloid found in barberry, goldenseal, Oregon grape, and Coptis, and has a long history in Chinese and Ayurvedic medicine for diarrhoea. In the United States and Europe it is sold as a dietary supplement, most often marketed for blood sugar and cholesterol; in parts of Asia it is used as a drug. The rationale in IBS-D draws on reported antimicrobial, anti-secretory, and anti-inflammatory actions and on effects on gut motility and visceral sensation PMID 26400188.

The IBS evidence is a single trial. Investigators in Shanghai recruited 196 patients with IBS-D and randomised 132 of them to berberine hydrochloride 400 mg twice daily or placebo for eight weeks, followed by a four-week washout, with daily diaries after a two-week run-in. Over the treatment period, berberine reduced the frequency of diarrhoea (p = 0.032), abdominal pain (p < 0.01), and urgent defecation (p < 0.01) more than placebo, and the authors reported a trend toward improvement in the overall IBS symptom score, depression and anxiety scores, and IBS quality of life. Berberine was described as well tolerated PMID 26400188. That is a reasonable first trial, but it is one centre, one population, and one preparation, and the abstract reports p-values rather than effect sizes for the main outcomes, so how much symptoms changed in practical terms is unclear from the published summary.

Caution deserves its own paragraph because berberine behaves more like a drug than a food. It is reported to inhibit several cytochrome P450 liver enzymes and the transporter P-glycoprotein, which can raise blood levels of medicines cleared by those routes, including some statins, immunosuppressants, and anticoagulants; anyone on regular prescriptions should check with a pharmacist before adding it. Because it is studied for lowering blood glucose, combining it with diabetes medication risks hypoglycaemia. It is advised against in pregnancy and breastfeeding, and it should not be given to newborns or infants, where it has been linked to jaundice and kernicterus by displacing bilirubin. It commonly causes constipation, cramping, or nausea at the doses used in trials, which is worth knowing in a condition defined by bowel symptoms.

Points clinicians commonly raise: a supplement label does not mean the product is inert, and berberine is a case where the pharmacology matters more than the marketing; the IBS-D result has not been replicated outside China; the trial ran for eight weeks, so nothing is known about longer use; and berberine’s effect on diarrhoea means it is not a candidate for IBS-C or mixed-type IBS on current evidence.

Talk to a clinician before starting or stopping anything.