A moderately high intake compared to a low intake of zinc depresses magnesium balance and alters indices of bone turnover in postmenopausal women

Abstract

Objectives: 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 mmol (2 mg) Cu and 137.7 mmol (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 mmol (1 mg) Cu/8.4 MJ, and the other group fed the same diet supplemented to provide 47.2 mmol (3 mg) Cu/ 8.4 MJ. After equilibration, both groups were fed the basal diet with no zinc supplemented (provided 45.9 mmol [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 mmol (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 þ 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 mmol/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 mmol/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.

Reported zinc, but not copper, intakes influence whole-body bone density, mineral content and T score responses to zinc and copper supplementation in healthy postmenopausal women

“…Bone mineral contents, densities and T scores were neither improved in women consuming , 0·9 mg/d Cu, nor exacerbated in women consuming $0·9 mg/d Cu, by the Zn plus Cu supplement. However, Cu intake might have had some effect on the Baseline 217 767 32 770 29 12·9 0·5 12·9 0·4 3·28 0·23 3·13 0·23 Year 1 181 803 36 771 31 13·3 0·6 12·5 0·4 3·50 0·25 3·18 0·23 Year 2 167 824 37 838 43 12·9 0·5 13·2 0·6 3·70 0·28 3·25 0·25 Post-year 3 150 804 34 802 37 13·0 0·5 12·4 0·5 3·73 0·28 3·30 (16) , and Mg deficiency may be a risk factor for bone loss in postmenopausal women (17) . Thus, an analysis was made of whether the negative response to Zn supplementation was greater with Mg intakes ,237 mg/d through exacerbating the negative effect of Mg deprivation on bone health.…”

“…Possible causes for the negative effect of Zn supplementation in women consuming $ the RDA for Zn was focused on a possible change in the status of a mineral involved in bone maintenance. In a controlled feeding study with postmenopausal women, high Zn intake (about 53 mg/d) v. a low Zn intake (about 3 mg/d) increased urinary N-telopeptide and decreased serum calcitonin concentrations (16) , which suggests that a high Zn intake may affect bone breakdown or Ca metabolism. Thus, Zn supplementation in excess of requirement may have prevented a beneficial action of Ca through interfering with Ca metabolism.…”

“…In an experiment performed on postmenopausal women, the high Zn intake (about 53 mg/d) compared with low Zn intake (about 3 mg/d) significantly increased the percentage of Mg intake found in both faeces and urine, which resulted in significantly decreased Mg balance or retention (16) . In rats, marginal Zn deficiency was found to increase Mg retention and impair Ca utilisation (24) .…”

The relationship between the zinc nutritive status and biochemical markers of bone turnover in older European adults: the ZENITH study

“…Within the ZENITH multi-centre prospective 6-month zinc intervention study, which employs a randomized double-blind design, we will be able to more directly assess the influence of altering zinc intake, and presumably therefore zinc status, on the rate of bone turnover in these older European adults. The only other intervention study that investigated the effect of zinc on bone metabolism was a recent study by Nielsen & Milne (2004). In this study, in which dietary zinc and copper intakes were altered in a factorial design, serum bone-specific alkaline phosphatase levels were unaffected but urinary levels of N-telopeptides of type I collagen (another biochemical marker of bone resorption: Cashman & Ginty, 2003) in postmenopausal women were, somewhat surprisingly, significantly increased on increasing zinc intake from 3 to 53 mg/d, irrespective of copper intake (Nielsen & Milne, 2004), raising some safety concerns.…”

“…The only other intervention study that investigated the effect of zinc on bone metabolism was a recent study by Nielsen & Milne (2004). In this study, in which dietary zinc and copper intakes were altered in a factorial design, serum bone-specific alkaline phosphatase levels were unaffected but urinary levels of N-telopeptides of type I collagen (another biochemical marker of bone resorption: Cashman & Ginty, 2003) in postmenopausal women were, somewhat surprisingly, significantly increased on increasing zinc intake from 3 to 53 mg/d, irrespective of copper intake (Nielsen & Milne, 2004), raising some safety concerns. Thus, the ZENITH study will help us advance our understanding of the role of zinc in bone health in the older adult age-group.…”