BOTH DIETARY 18 2 AND 16/0 MAY BE REQUIRED TO IMPROVE THE SERUM LDL/HDL CHOLESTEROL RATIO IN NORMOCHOLESTEROLEMIC MEN/

In a double-blind crossover study, 23 healthy normocholesterolemic mal e volunteers were fed carefully designed whole food diets enriched by oleic acid (canola, CAN), palmitic acid (palm olein, POL), or an Ameri can Heart Association Step 1 fat blend (AHA). Resident males received each diet during three consecutive 4-week periods. The diets supplied approximately 31% energy as fat and <200 mg of cholesterol/day. The pe rcent energy (% en) from each dietary fatty acid was strictly controll ed to compare low-16:0, high-18:1 (CAN) or high-16:0, Iow-18:2 (POL) i ntake with a balanced intake of each (AHA). The first two diets repres ented direct exchange of 7% en between 18:1 + 18:2 (CAN) and 16:0 (POL ), whereas the main difference between POL and AHA was <4% en exchange d between 16:0 and 18:2. Serum total cholesterol (TC), very low densit y lipoprotein cholesterol (VLDL-C), and LDL-C were not significantly a ffected by the three diets despite manipulation of these key fatty aci ds. However, both CAN (low saturates [SATs], high monounsaturates [MON Os]) and POL (high SATs, low polyunsaturates [POLYs]) depressed HDL-C significantly (-8 mg/dL) relative to the AHA (mod SATs, mod POLYs) die t. Consequently, the AHA diet increased HDL(3)-C and lowered the LDL/H DL cholesterol ratio significantly relative to the CAN and POL diets. Neither serum Lp(a), apoA1, nor apoB were affected by diet. These data support the previous observation that in normolipemic humans consumin g a moderate fat load (<31% en) low in myristic acid (14:0) and dietar y cholesterol, the effect of palmitic acid (16:0) on TC and the LDL/HD L ratio is comparable to that of monounsaturated oleic acid (18:1). Fu rthermore, a definite intake of POLYs and SATs may be essential for ma ximizing HDL(3)-C under these conditions.