HOMEOSTATIC REGULATION OF ZINC-ABSORPTION AND ENDOGENOUS LOSSES IN ZINC-DEPRIVED MEN

The mechanisms involved in the homeostatic regulation of zinc were studied in five male subjects by using stable Zn-70 as a marker. When dietary zinc was reduced from 85 to 12-mu-mol/d, adaptation was achieved by a mean (+/- SEM) reduction in urine zinc of 48 +/- 7% and in fecal zinc of 46 +/- 12% over 25 d in four subjects. The latter was caused by an increase in the efficiency of zinc absorption from 38 +/- 3% to 93 +/- 1% after 15 d of zinic deprivation and by a reduction in intestinal endogenous losses of zinc. In a fifth subject, who had some evidence of a resolving alcohol-induced hepatitis, urine and fecal zinc were reduced by 64% and 41%, respectively, in 15 d and zinc absorption increased from 46% to 93%. More information on adaptive responses is needed to enable current dietary recommendations to be reconsidered.