Coffee drinking increases levels of urinary hydrogen peroxide detected in healthy human volunteers.

Freshly-voided human urine contains significant concentrations of hydrogen peroxide (H2O2). This H2O2 appears to arise in whole or in part by superoxide-dependent autoxidation of urinary biomolecules. Since instant coffee also contains high levels of H2O2, we examined the effect of coffee drinking on urinary levels of H2O2. Studies on healthy human volunteers showed that coffee drinking is rapidly and reproducibly followed by increased levels of H2O2 detectable in the urine for up to 2 h after drinking the coffee. The levels of H2O2 detected in urine suggest that exposure of human tissues to H2O2 may be greater than is commonly supposed. It is possible that H2O2 in urine could act as an antibacterial agent, and that H2O2 is involved in the regulation of glomerular function.