Level of polyunsaturated fatty acids and the n-6 to n-3 polyunsaturated fatty acid ratio in the rat diet alter serum lipid levels and lymphocyte functions.Prostaglandins Leukot Essent Fatty Acids 1997; 57(2):149-60PL
In order to further examine the effects of dietary polyunsaturated fatty acids (PUFA) upon blood lipid levels and lymphocyte functions, weanling rats were fed for 6 weeks on high fat (178 g/kg) diets which differed in the ratio of n-6:n-3 PUFA (100, 20, 10, 5, 1) and in the absolute level of PUFA (17.5 or 35 g/100 g fatty acids). The n-6:n-3 PUFA ratio of the diets was decreased by replacing linoleic acid with alpha-linolenic acid while the PUFA content of the diets was decreased by replacing PUFA with palmitic acid. Serum cholesterol concentrations decreased as the n-6:n-3 PUFA ratio of the low PUFA diet decreased. The ex vivo proliferation of spleen lymphocytes from rats fed the low PUFA diets decreased as the n-6:n-3 PUFA ratio of the diet decreased; the proliferation of spleen lymphocytes from high PUFA-fed rats was less affected by the n-6:n-3 PUFA ratio of the diet. Natural killer cell activity was lower for spleen lymphocytes from rats fed high PUFA diets with n-6:n-3 PUFA ratios of 100 or 20 than for those from rats fed low PUFA diets with these ratios. The natural killer cell activity of spleen lymphocytes decreased as the n-6:n-3 PUFA ratio of the low PUFA diet decreased. These findings indicate that dietary alpha-linolenic acid has significant blood lipid-lowering and immunomodulatory effects in rats, but that the effect is dependent upon the total PUFA content of the diet. The ratios of linoleic and alpha-linolenic acids to other fatty acids (e.g. palmitic, oleic) are important in determining the precise effect of manipulations of the fatty acid composition of the diet.