Piperine and bioavailability: a real mechanism, routinely overstated

Black pepper's piperine is the stock example of a "bioavailability enhancer", and it is a real effect with a real mechanism — the overstatement is in the size and the breadth of the claims. The mechanism, specifically Piperine inhibits several CYP enzymes (including CYP3A4) and UGT glucuronidation, and inhibits P-glycoprotein efflux. Less first-pass metabolism and less efflux back into the gut lumen means more of a susceptible compound reaches the blood. It is the same family of mechanism as the grapefruit interaction, with a different inhibitor. The famous number The widely cited figure is a ~20-fold increase in curcumin bioavailability from 20 mg piperine with 2 g curcumin (Shoba G et al., Planta Med 1998). That is one small study, one compound with famously poor baseline absorption, and a relative increase off a tiny base. It does not generalise to "piperine boosts everything by 20x". Why this belongs on a pharmacology board, not just a supplement board Because piperine is a CYP/UGT/P-gp inhibitor, adding it to a stack is adding a drug-interaction agent. It can raise levels of co-taken medicines that share those pathways — the same way grapefruit does. "Natural" does not exempt it from the interaction logic. Black pepper also carries guineensine (an endocannabinoid reuptake inhibitor) and beta-caryophyllene (a CB2 agonist), so it is pharmacologically busier than "just piperine". Mechanism and synergy framing: https://wiki.soapbox.community/wiki/Bioavailability_Metabolic_Inhibition_and_Synergy and https://wiki.soapbox.community/wiki/Black_Pepper