Black Pepper

Black pepper's active compound is piperine. It's what creates the bite, and it interacts with the body in a few measurable ways — the most studied being a substantial increase in the bioavailability of curcumin (the active compound in turmeric). Without piperine, curcumin is poorly absorbed; with it, plasma levels rise about 20-fold. That's why most turmeric supplements include black pepper.

Reflux and gastric irritation

Piperine relaxes the lower esophageal sphincter and stimulates gastric acid secretion. For people prone to GERD, even modest amounts of black pepper can trigger heartburn. It's also a common irritant for active stomach ulcers or gastritis flares.

Drug interactions

Because piperine inhibits drug-metabolizing enzymes (CYP3A4) and the P-glycoprotein transporter, it can raise blood levels of certain medications — including some statins, calcium channel blockers, and immunosuppressants. The amounts used in cooking are unlikely to cause clinical issues, but high-dose piperine supplements (sold for absorption-enhancement) can.

In normal culinary use, black pepper is fine and offers mild antioxidant activity. The issues are concentrated in two situations: people with active reflux and people taking high-dose supplemental piperine.