Generation of hydrogen peroxide by “Antioxidant” beverages and the effect of milk addition. Is cocoa the best beverage?

The ability of several beverages to generate hydrogen peroxide was demonstrated by direct measurement using the ferrous ion oxidation-xylenol orange (FOX) assay. Tea and coffee could generate H2O2 to achieve levels over 100 microM, but cocoa did not. Milk decreased net H2O2 production by beverages and showed some ability to remove H2O2 itself, apparently not because of catalase activity. Hence several of the beverages commonly drunk by humans show a complex mixture of anti- and pro-oxidant abilities.