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Abstract
Zinc is essential to the growth and health of humans and may influence many health outcomes. An index of usual zinc intake over a given period is needed. The purpose of this study was to investigate whether or not zinc concentration in erythrocytes is an index of usual dietary intake of zinc during preceding months. In a cross-sectional study, 134 healthy, nonpregnant black women contributed blood and were interviewed to determine usual food consumption during the previous year and sociodemographic characteristics. The primary method of analysis was computation of correlation coefficients between the primary variables: dietary zinc (from food sources only) and zinc concentration in erythrocytes ($\mu$g zinc/gm hemoglobin). The effect of numerous demographic, medical, and dietary variables upon the estimated correlation between the primary variables was assessed by analysis of subgroups and by ranked partial correlation coefficients. The correlation between dietary zinc and erythrocyte zinc in the study group (N = 134) was weakly negative (Spearman r = $-$0.09, P = 0.29). A restricted group (N = 74) was defined which excluded subjects for methodological reasons (differences in recruitment and interview procedures) or medication use (consumption of diuretics or selected vitamin/mineral supplements). In this group, the correlation between dietary zinc and erythroctye zinc was slightly positive (Spearman r = 0.17, P = 0.16). With control for linoleic acid, the correlation in the restricted group became slightly more positive (ranked partial r = 0.25, P = 0.03). Mean erythrocyte zinc ($\mu$g zinc/gm hemoglobin) was found to be lower in subjects who currently smoked cigarettes than in nonsmokers (P = 0.04) and higher in subjects with a history of elevated blood cholesterol or triglycerides than in remaining subjects (P = 0.02). It was concluded that erythrocyte zinc probably is not an index of dietary zinc during preceding months among healthy women eating an unrestricted diet, that modifications in collection of data about nutrient intake from supplements should be considered, and that hypotheses regarding the effect of lipids upon erythrocyte zinc merit evaluation in other studies.
