Intestinal absorption and losses of copper measured using 65Cu in zinc-deprived men

The absorption and intestinal losses of endogenous Cu in response to a low Zn diet were studied in five young male subjects using stable 65Cu as an oral tracer. The subjects received a semi-purified formula diet providing 85 mumol (5.6 mg) Zn/d during 15-day baseline and repletion phases and 12 mumol (0.8 mg) Zn/d during an intervening period of 25 days. Thirty-eight mumol (2.4 mg) Cu/d was provided throughout the study. In four of the subjects, the mean +/- SEM luminal disappearance of 65Cu was 37 +/- 4 per cent during the baseline phase and was unaffected by Zn deprivation (32 +/- 7 per cent) or repletion (30 +/- 7 per cent) as were intestinal losses of endogenous Cu [7 +/- 4, 8 +/- 3, 8 +/- 3 mumol/d (0.4 +/- 0.1, 0.5 +/- 0.1, 0.5 +/- 0.1 mg/d) during baseline, Zn deprivation and Zn repletion phases, respectively]. In a fifth subject, who had some evidence of a resolving alcohol-induced hepatitis, the luminal disappearance of 65Cu was 31, 44 and 42 per cent and the intestinal losses of endogenous Cu 11, 2 and 6 mumol/d (0.7, 0.1 and 0.4 mg/d) during the baseline, Zn deprivation and Zn repletion phases respectively. Plasma Cu concentrations, however, fell throughout the study in all the subjects, despite consistently positive Cu balances. There may be subtle effects of a low dietary intake of Zn on Cu metabolism which were not revealed by the methods used in this study.