Effect of dietary linoleic acid on the tissue levels of zinc and copper, and serum high density lipoprotein cholesterol

Abstract

The effects of dietary linoleic acid on the serum level of high density lipoprotein (HDL) cholesterol and its relationship with the tissue status of zinc and copper were examined in adult male rats fed diets differing in the amount of linoleic acid. One group of 9 animals was fed a diet containing hydrogenated coconut oil (4%) and the other was fed a diet containing coconut oil (3.4%) plus linoleic acid (0.6%). Both diets were isocalorically formulated with the equal levels of minerals and other nutrients and contained cholesterol at 1% level. During a 6-week experiment, no differences were observed in food intake and body weight between the two groups. The feeding of linoleic acid produced a significant decrease in serum HDL cholesterol level at 6 weeks and no changes in other lipoproteins and total serum cholesterol and triglyceride. Dietary linoleic acid also significantly lowered the concentrations of zinc in serum and tibia at 6 weeks, while it had no effect on copper contents in these tissues. No changes were observed in the concentration of either zinc or copper in the liver. Linear regression analysis of the 18 pairs of serum zinc and HDL values at 6 weeks indicated a significant positive correlation ( r = + 0.65; P < 0.01) between the two parameters. No such relationships were shown between tibia zinc and serum HDL, and between tissue copper and serum HDL. The results indicate that dietary linoleic acid at a relatively low level produces a decrease in serum HDL cholesterol without significantly lowering total serum cholesterol and that the decrease in HDL cholesterol due to linoleic acid feeding is significantly correlated with the reduction in serum zinc level.