Possible cocarcinogenic effects of coffee constituents

Abstract

ALTHOUGH the carcinogenic properties of secondary N-nitro-samines and related compounds are well established^1,2, their causal relationship to human cancer remains an open question because very little is known about the degree of human exposure to them. Carcinogenic N-nitrosamines have been detected in some nitrite-preserved foodstuffs, but only at relatively low levels^3,4, so the major uncertainty comes from their formation in vivo from ingested nitrite and amino compounds. Formation of N-nitrosamines in this way in the digestive tract of laboratory animals has been widely demonstrated (for typical examples, see refs 5–7) and has led to the induction of tumours characteristic of N-nitrosamines^8,9. We have suggested¹⁰ that the interaction between nitrite and phenolic materials should also be considered, because the latter are major dietary constituents which usually react much more rapidly than most amino compounds with nitrous acid. Certain natural phenols may therefore inhibit N-nitrosamine formation both in foodstuffs and in the digestive tract. We report here, however, that readily oxidised phenolic compounds act as catalysts rather than inhibitors for N-nitrosamine formation from nitrite salts and secondary amines at gastric pH. This finding has important implications on the possible cocarcinogenic properties of several foodstuffs and beverages, including coffee.