¹US Department of Agriculture, Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, ND, USA

Correspondence: FH Nielsen, US Department of Agriculture. Agricultural Research Service, Grand Forks Human Nutrition Research Center, PO Box 9034, Grand Forks, ND 58202-9034, USA. E-mail: fnielsen@gfhnrc.ars.usda.gov

²Now retired.

³Current address: PO Box 366, Gallatin Gateway, MT 59730, USA.

The US Department of Agriculture, Agricultural Research Service, Northern Plains Area, is an equal opportunity/affirmative action employer, and all agency services are available without discrimination. Mention of a trademark or proprietary product does not constitute a guarantee or warranty by the US Department of Agriculture and does not imply its approval to the exclusion of other products that also might be suitable. This study was supported in part by the International Lead Zinc Organization. Portions of these data were presented at the VIth Conference of the International Society for Trace Element Research In Humans, Quebec City, Quebec, Canada, and published in abstract form (J. Trace Elem. Exp. Med. 14, 286–287, 2001).

Contributors: The study was designed and supervised by DBM and FHN. The paper was written by FHN.

Guarantor: FH Nielsen.

Received 28 January 2003; Revised 14 March 2003; Accepted 25 March 2003.

Abstract

Objective: To determine whether moderately high or low intakes of zinc adversely affect the copper status of postmenopausal women to result in unfavorable changes in calcium and magnesium metabolism and other indicators of bone turnover.

Design: After a 10-day equilibration period in which the diet provided 31.5 mol (2 mg) Cu and 137.7 mol (9 mg) Zn/8.4 MJ (2000 kcal), the subjects were randomly divided into two groups, with one group fed the basal diet supplemented to provide15.7 mol (1 mg) Cu/8.4 MJ, and the other group fed the same diet supplemented to provide 47.2 mol (3 mg) Cu/8.4 MJ. After equilibration, both groups were fed the basal diet with no zinc supplemented (provided 45.9 mol [3 mg] Zn/8.4 MJ) for 90 days; this was followed by another 10-day equilibration period before the basal diet was supplemented with zinc to provide 811 mol (53 mg)/8.4 MJ for 90 days.

Setting: The metabolic unit of the Grand Forks Human Nutrition Research Center, Grand Forks, ND, USA.

Subjects: A total of 28 postmenopausal women recruited by advertisement throughout the United States of America. Among them, 25 women (64.9+6.7 y) completed the study; 21 as designed.

Results: The moderately high intake compared to the low intake of zinc increased the excretion of magnesium in the feces and urine, which resulted in a decreased magnesium balance. In the women fed low dietary copper, plasma osteocalcin was higher during the low-zinc than high-zinc dietary period. The urinary excretion of N-telopeptides was increased and the serum calcitonin concentration was decreased by high dietary zinc regardless of dietary copper.

Conclusions: A moderately high intake of zinc (811 mol/day; 53 mg/day) did not induce changes in copper metabolism that resulted in unfavorable changes in bone or mineral metabolism. However, low dietary zinc (45.9 mol/day; 3 mg/day) apparently resulted in undesirable changes in circulating calcitonin and osteocalcin. As a moderately high intake of zinc decreased magnesium balance, further study of the possibility that a high intake of zinc is a health concern for individuals consuming less than the recommended amounts of magnesium is warranted.