Effect of zinc supplementation on serum zinc concentration and T cell proliferation in nursing home elderly: a randomized, double-blind, placebo-controlled trial
Barnett, J.B.; Dao, M.C.; Hamer, D.H.; Kandel, R.; Brandeis, G.; Wu, D.; Dallal, G.E.; Jacques, P.F.; Schreiber, R.; Kong, E.; Meydani, S.N.
American Journal of Clinical Nutrition 103(3): 942-951
ISSN/ISBN: 0002-9165 PMID: 26817502 DOI: 10.3945/ajcn.115.115188
Zinc is essential for the regulation of immune response. T cell function declines with age. Zinc supplementation has the potential to improve the serum zinc concentrations and immunity of nursing home elderly with a low serum zinc concentration. We aimed to determine the effect of supplementation with 30 mg Zn/d for 3 mo on serum zinc concentrations of zinc-deficient nursing home elderly. This was a randomized, double-blind, placebo-controlled study. Of 53 nursing home elderly (aged ≥65 y) who met eligibility criteria, 58% had a low serum zinc concentration (serum zinc <70 μg/dL); these 31 were randomly assigned to zinc (30 mg Zn/d) (n = 16) or placebo (5 mg Zn/d) (n = 15) groups. The primary outcome measure was change in serum zinc concentrations between baseline and month 3. We also explored the effects of supplementation on immune response. Baseline characteristics were similar in the 2 groups. The difference in the mean change in serum zinc was significantly higher, by 16%, in the zinc group than in the placebo group (P = 0.007) when baseline zinc concentrations were controlled for. In addition, controlling for baseline C-reactive protein, copper, or albumin did not change the results. However, supplementation of participants with ≤60 μg serum Zn/dL failed to increase their serum zinc to ≥70 μg/dL. Zinc supplementation also significantly increased anti-CD3/CD28 and phytohemagglutinin-stimulated T cell proliferation, and the number of peripheral T cells (P < 0.05). When proliferation was expressed per number of T cells, the significant differences between groups were lost, suggesting that the zinc-induced enhancement of T cell proliferation was mainly due to an increase in the number of T cells. Zinc supplementation at 30 mg/d for 3 mo is effective in increasing serum zinc concentrations in nursing home elderly; however, not all zinc-deficient elderly reached adequate concentrations. The increase in serum zinc concentration was associated with the enhancement of T cell function mainly because of an increase in the number of T cells.