Berberine

Berberine is an alkaloid found in barberry, goldthread, goldenseal and Oregon grape. Memorial Sloan Kettering's About Herbs summary describes meta-analyses suggesting small improvements in lipids and blood sugar from mostly low-quality trials, and notes that berberine lowered the risk of colorectal adenoma recurrence. That finding comes from a double-blind randomised trial at seven Chinese hospitals (Chen et al., Lancet Gastroenterology and Hepatology 2020): among people who had adenomas removed, 36 per cent taking berberine 0.3 g twice daily and 47 per cent taking placebo had a recurrent adenoma during follow-up (relative risk 0.77), with no serious adverse events. Adenomas are a precursor rather than cancer, no cancers were detected in either group, and the result has not yet been repeated outside China, so this is a promising prevention signal rather than a recommendation. Berberine has not been tested as a treatment for cancer. MSK lists interactions: repeated doses reduced the activity of CYP2D6, CYP2C9 and CYP3A4 in people; it raised tacrolimus levels with kidney toxicity in a child and raised ciclosporin levels in transplant recipients; and modelling predicts a 1.3-fold increase in exposure to bosutinib but not imatinib. It should be avoided in pregnancy and breastfeeding.