Effect of dietary zinc and copper on plasma zinc, copper, total cholesterol in young adult males

An eight week controlled feeding study was conducted to determine the effects of dietary zinc and copper on plasma zinc, copper, total cholesterol (TC), and high density lipoprotein cholesterol (HDL-C) levels in young adult males receiving two levels of zinc. Source of dietary calcium was also varied, however possible interactions or effects of calcium were not determined in this study. Subjects consumed zinc supplements of 10 mg/day, in combination with 1 of 3 diets, resulting in zinc:copper ratios of 30: 1 (Dairy Calcium, or DC group), 20:1 (Control or CO group), and 20:1 (Calcium Carbonate or CC group). Copper content of all diets was approximately 1 mg/day. Plasma levels of zinc, copper, TC, and HDL-C did not differ significantly between the groups. However, plasma levels of copper, zinc, and HDL-C, were found to be significantly affected by the specific week of controlled feeding across all 3 groups (p<.05). Plasma copper at baseline was significantly lower than at weeks 2,4,6, 8, and post treatment. Plasma zinc at baseline, and weeks 2 and 4, was found to be significantly lower than at weeks 6, 8, and post treatment. At week 6, plasma HDL-C was noted to be significantly higher than at baseline, weeks 2, 4, 8, and post treatment. Spearman correlation coefficients determined negative correlations between plasma copper and TC (r=-0.39, p<0.04), and plasma copper and zinc (r=-0.43, p<0.02) in the DC group. A positive correlation was also noted between plasma zinc and TC (r=0.32, p<0.10) in the DC group. Plasma copper and HDL-C were determined to be negatively correlated in the CO group (r=-0.48, p<0.005). Plasma zinc and HDL-C were found to be negatively correlated in the CC group (r=-0.58, p<0.001).