Low dietary zinc alters indices of copper function and status in postmenopausal women , ,

OBJECTIVES: To better define the relationship between dietary zinc and copper for humans so that sound recommendations for intakes of these elements can be made. METHODS: A study was conducted to ascertain the effect of moderately excessive and deficient intakes of zinc on copper metabolism and use in humans fed low and luxuriant amounts of copper. Twenty-one postmenopausal women housed in a metabolic unit completed the study as designed. After a 10-d equilibration period in which they were fed a diet providing 31.5 μmol (2 mg) Cu and 91.8 μmol (9 mg) Zn/8.4 MJ (2000 kcal), the women were divided into two groups. One group was fed a diet containing 15.7 μmol (1 mg) Cu/8.4 MJ (2000 kcal), and the other group was fed a diet containing 47.2 μmol (3 mg) Cu/8.4 MJ (2000 kcal). After equilibration, both groups were fed the basal diet providing 45.9 μmol (3 mg) Zn/8.4 MJ (2000 kcal) for 90 d; this was followed by another 10-d equilibration period before dietary zinc was increased to 811 μmol (53 mg)/8.4 MJ (2000 kcal) for 90 d. RESULTS: The women were in positive copper balance only when the diet provided 47.2 μmol (3 mg) Cu and 811 μmol (53 mg) Zn/d. Immunoreactive ceruloplasmin concentrations and platelet cytochrome-c oxidase activity on a platelet number basis were significantly lower and the ratio between enzymatic and immunoreactive ceruloplasmin was significantly higher during low dietary than during high dietary zinc intake. Serum cholesterol was higher in subjects fed 15.7 μmol (1 mg) Cu/d than in those fed 47.2 μmol (3 mg) Cu/d. Total and low-density lipoprotein cholesterol concentrations decreased with zinc supplementation. Whole-blood glutathione concentration and erythrocyte glutathione peroxidase activity were lower during high than during low dietary zinc intake. CONCLUSIONS: The findings indicate that an inadequate intake of zinc (45.9 μmol/d; 3 mg/d) was more effective than a moderately high intake of zinc (811 μmol/d; 53 mg/d) in inducing changes associated with a decreased copper status in postmenopausal women. Furthermore, the findings indicate that copper status indicators might be useful in evaluating changes in zinc status in humans, and an intake of 15.7 μmol (1 mg)/d of copper may be inadequate for postmenopausal women.