MICRONUTRIENT ROLES IN PHYSIOLOGY AND HEALTH
Location: Grand Forks Human Nutrition Research Center
Title: 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
Submitted to: British Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 28, 2011
Publication Date: July 5, 2011
Citation: Nielsen, F.H., Lukaski, H.C., Johnson, L.K., Roughead, Z.K. 2011. 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. British Journal of Nutrition. 106:1872–1879.
Interpretive Summary: It is generally agreed that inadequate calcium and vitamin D are significant nutritional concerns for bone growth and maintenance and thus are risk factors for bone loss leading to osteoporosis. Limited evidence from small supplementation trials suggests that other minerals, including copper and zinc, also may be of nutritional concern for bone health. In addition, animal studies have shown relatively severe copper deficiency adversely affects bone strength and zinc deficiency adversely affects bone turnover. Thus, a supplementation trial starting with a relatively large number of postmenopausal women was conducted to determine whether increased copper and zinc intakes would reduce the risk for bone loss. Women aged 51 to 80 years were assigned to two groups of 112 each that were supplemented daily for two years with 600 milligrams of calcium plus a cornstarch placebo or 600 milligrams of calcium plus 2 milligrams of copper and 12 milligrams of zinc. Both groups were given a multivitamin that provided adequate vitamin D. Whole body bone mineral contents, densities, and T scores were determined biannually by dual x-ray absorptiometry and 5-day food diaries were obtained annually. The T score was a measure of how much different bone mineral density was from a value obtained from healthy young individuals. Bone mineral content, density and T score were not prevented from decreasing from baseline to the end of the study by either treatment. However, analysis of results from each treatment individually between baseline and year two showed that the copper and zinc supplement exacerbated instead of alleviated the decreased bone status. Based on 5-day food diaries, the negative effect was judged to be caused by zinc and almost entirely occurred in women with zinc intakes higher than the Recommended Dietary Allowance (RDA) of 8.0 milligrams per day. The total intake of these women with the 12 milligram zinc supplement ranged from 20 to 44 milligrams per day, which is about 3 to 6 times the RDA. When zinc intakes were less than the RDA, zinc supplementation, resulting in intakes up to 20 milligrams per day, apparently was beneficial. Based on copper intakes indicated by 5-day food diaries, the copper supplementation apparently did not have an adverse impact on whole body bone content, density, or T score. Food diaries also indicated that copper intakes less than the RDA of 0.9 milligrams per day and zinc intakes less than the RDA of 8.0 milligrams per day, as well as magnesium intakes less than 237 milligrams per day are associated with poorer bone health. A national survey indicated that over 25% of U.S. women older than age 51 have usual magnesium intakes lower than 237 milligrams per day. The findings indicate that zinc supplementation is beneficial to bone health in postmenopausal women with usual zinc intakes less than the RDA, but might be detrimental if supplementation results in excessive intakes of zinc. In addition, findings were obtained indicating that inadequate intakes of copper, zinc and magnesium might be nutritional concerns for bone health.
A supplementation trial starting with 224 postmenopausal women provided with adequate vitamin D and calcium was conducted to determine whether increased copper and zinc intakes would reduce the risk for bone loss. Healthy women aged 51-80 years were recruited for a double-blind, placebo-controlled study. Women with similar femoral neck T scores and body mass indexes were randomly assigned to two groups of 112 each that were supplemented daily for 2 years with 600 mg calcium plus cornstarch placebo or 600 mg calcium plus 2 mg copper and 12 mg zinc. Whole body bone mineral contents, densities, and T scores were determined biannually by dual x-ray absorptiometry and 5-day food diaries were obtained annually. Repeated measures ANCOVA showed that bone mineral contents, densities, and T scores decreased from baseline values to year 2. A priori contrasts between baseline and year two indicated that the greatest decreases occurred with copper and zinc supplementation. Based on 5-day food diaries, the negative effect was caused by zinc and mainly occurred with zinc intakes =8.0 mg/d. With zinc intakes <8.0 mg/d, zinc supplementation apparently prevented a significant decrease in whole body bone densities and T scores. Food diaries also indicated that magnesium intakes <237 mg/d, copper intakes <0.9 mg/d, and zinc intakes <8.0 mg/d are associated with poorer bone health. The findings indicate that zinc supplementation may be beneficial to bone health in postmenopausal women with usual zinc intakes <8.0 mg/d but not in women consuming adequate amounts of zinc.