The effect of experimental zinc depletion on the intestinal absorption of mono- and polyglutamyl folates was assessed in six healthy male subjects by measuring the increase in serum folate after an oral dose of pteroylmonoglutamate and pteroylheptaglutamate before and after initiation of a zinc-deficient diet. At the beginning of the study, no differences were detected in the absorption of pteroylmono- and heptaglutamate. After zinc depletion, the rise in serum folate after an oral dose of pteroylheptaglutamate was reduced by an average of 53% while pteroylmonoglutamate absorption appeared to be unchanged. These data suggest that zinc depletion results in a decreased intestinal hydrolysis of pteroylpolyglutamate and that intestinal conjugase in man is a zinc-dependent enzyme.
