EFFECTS OF HIGH MONOUNSATURATED AND POLYUNSATURATED FAT DIETS ON PLASMA-LIPOPROTEINS AND LIPID-PEROXIDATION IN TYPE-2 DIABETES-MELLITUS

Increased free radical peroxidation of lipoproteins may contribute to the excess atherosclerosis in Type 2 diabetes mellitus and may be aggravated by increasing polyunsaturate intake. Increasing intake of monounsaturates might have similar hypolipidaemic effects while avoiding this problem. Therefore the effects of high monounsaturated and polyunsaturated fat diets on plasma lipoproteins and lipid peroxidation were compared, against each other and a relatively high saturated fat baseline diet, in 13 men with Type 2 diabetes and 12 healthy controls, randomized in crossover fashion to each diet. There were no differences in plasma lipoproteins between the monounsaturated and polyunsaturated fat diets in the diabetic and control groups separately, but when both groups were combined, high density lipoprotein cholesterol was higher on the monounsaturated fat diet (p = 0.04). Plasma lipid peroxidation was similar on the monounsaturated and polyunsaturated fat diets in both groups, but all indices of plasma lipid peroxidation in the diabetic group and lipid peroxides in the controls were significantly lower on these diets compared to the baseline diet. Both high monounsaturated and polyunsaturated fat diets increase hepatic metabolism of low density lipoprotein and shorten its circulating half-life and both may reduce lipid peroxidation, compared to high saturated fat diets, by this mechanism. On high polyunsaturated fat diets, this effect may offset any increased susceptibility of polyunsaturate enriched low density lipoprotein to peroxidation.