Relationships of dietary zinc/copper ratios to plasma cholesterol and liver trace mineral deposition in young rats fed saturated and unsaturated fats

The effects of copper and zinc supplements on weight gains, plasma total and high density lipoprotein (HDL)-cholesterol levels and liver trace mineral levels were studied in young rats fed either coconut oil or corn oil. Dietary factors included 1.5 ppm and 6 ppm copper, 7.5 ppm and 30 ppm zinc, and the two fat sources. Weight gains and levels of total and HDL-cholesterol were higher in rats fed corn oil than in rats fed coconut oil. Increases in dietary zinc were associated with increases in total and HDL-cholesterol levels in rats fed corn oil, while increases in copper supplements were associated with decreases in total and HDL-cholesterol levels in rats fed either fat source. Supplements of 30 ppm zinc resulted in decreases in total cholesterol/HDL-cholesterol ratios in rats fed coconut oil but had no apparent effect on these ratios in rats fed corn oil. Thus, zinc may be a more important factor than copper in the reduction of this ratio, particularly if saturated fatty acids predominate in the diet. Increases in dietary copper were associated with increases in liver copper levels of rats fed either fat source. Increases in either dietary copper or zinc resulted in decreases in liver iron deposition in rats fed both fat sources. Results of this study indicate that a dietary zinc/copper ratio of 5 may be required for optimum growth of young rats.