PLASMA AND ERYTHROCYTE ZINC CONCENTRATIONS AND THEIR RELATIONSHIP TO DIETARY ZINC INTAKE AND ZINC SUPPLEMENTATION DURING PREGNANCY IN LOW-INCOME AFRICAN-AMERICAN WOMEN

Objective To evaluate the effects of usual dietary intake of zinc and of zinc supplementation during pregnancy on plasma and erythrocyte zin c concentrations. Design A randomized, double-blind, placebo-controlle d trial. Subjects Low-income African-American women (n=580) assigned r andomly to groups at 19 weeks of gestation. Intervention A daily dose of zinc (25 mg) or a placebo until delivery. Main outcome measures Pla sma, erythrocyte, and dietary zinc levels Statistical analyses Multipl e regression and repeated measures analysis of variance. Results In bo th the placebo and the supplemented groups, when all subjects were gro uped by usual dietary zinc intake above or below the median (12 mg/day ), results were the same: Women with high dietary zinc intake had high er erythrocyte zinc levels at the time of randomization and at all sub sequent measurements during pregnancy than those who had low dietary z inc intake (P less than or equal to.06; difference not significant for zinc-supplemented group); no difference was observed for plasma zinc levels. On the other hand, when the subjects were stratified at the me dian by total daily zinc intake (usual dietary zinc + 25 mg zinc suppl ement) during pregnancy, a significant difference in plasma zinc level s (P<.005) was found between women with high total zinc intake (mean=3 8 mg/day) and low total intake (mean=13 mg/day) at 26, 32, and 38 week s of gestation; however, no such differences were found in erythrocyte zinc levels.Applications These results should help dietitians and oth er health professionals better understand the expected changes in plas ma and erythrocyte zinc levels during pregnancy, and the relationship between dietary and supplemental zinc and zinc nutriture.