POLYUNSATURATED FATTY-ACIDS RESULT IN GREATER CHOLESTEROL-LOWERING AND LESS TRIACYLGLYCEROL ELEVATION THAN DO MONOUNSATURATED FATTY-ACIDS IN A DOSE-RESPONSE COMPARISON IN A MULTIRACIAL STUDY-GROUP

Cholesterol-lowering effects of polyunsaturated and monounsaturated fa tty acids were compared as they were varied in a reciprocal dose-depen dent fashion in the context of a National Cholesterol Education Progra m (NCEP) Step 1 diet. The study population comprised 63 moderately hyp ercholesterolemic African American and white men and women. After a 6- wk baseline diet containing 37% of energy from total fat and 15% from saturated fat, participants consumed four diets for 6 wk each, in rand om order, containing 10% of energy as saturated fatty acids; 3%, 6%, 1 0%, and 14% of energy as polyunsaturated fatty acids; and 17%, 14%, 10 %, and 6% of energy as monounsaturated fatty acids. Dietary cholestero l, fiber, plant sterol, and squalene contents were constant with all f our diets. There was a progressive decrease in total (P = 0.028) and l ow-density-lipoprotein cholesterol (P = 0.184) across the four diets, with the greatest decrease observed in the diet with the highest conte nt of polyunsaturated fatty acids; a small but significant decrease in high-density-lipoprotein (HDL) cholesterol that did not show a trend between the polyunsaturated and monounsaturated diets; and a trend bet ween the four diets in triacylglycerol elevations (P = 0.029), with th e smallest increment occurring in the diets highest in polyunsaturates . The magnitude of the cholesterol-lowering response was greater in th ose with higher baseline cholesterol and less in those who were more o bese. The dietary response was similar in both ethnic groups and in bo th sexes. In conclusion, in an NCEP Step 1 diet containing 30% total f at, with all other known cholesterol-influencing dietary factors held constant, the substitution of polyunsaturated fatty acid for monounsat urated fatty acid from 3% to 14% resulted in a progressive decline in total cholesterol and less triacylglycerol elevations, without effect on HDL cholesterol.