An investigation into the effect of different intakes of vitamin C on drug metabolism in Gambian men

Hepatic mixed-function oxidase activity was measured in Gambian men during a period of low seasonal vitamin C intake and after vitamin C supplementation. Demethylation of methoxyphenylacetamide (methacetin) was followed using a breath test, in which the exhalation of 13C-enriched CO2 was measured following an oral dose of 13C-methacetin. Vitamin C supplementation, sufficient to increase plasma levels significantly, did not influence methacetin metabolism. However, methacetin metabolism in unsupplemented men appeared normal in the majority of cases. Hepatic tissue may not have been sufficiently depleted of vitamin C to impair the activity of the mixed function oxidase system.