Abstract
In a double-blind crossover study, 23 healthy normocholesterolemic mals volunteers were fed carefully designed whole food diets enriched by oleic acid (canola, CAN), palmitic acid (palm olein, POL), or an American 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 percent energy (% en) from each dietary fatty acid was strictly controlled to compare low-16:0, high-18:1 (CAN) or high-16:0, low-18:2 (POL) intake with a balanced intake of each (AHA). The first two diets represented 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 exchanged between 16:0 and 18:2. Serum total cholesterol (TC), very low density lipoprotein cholesterol (VLDL-C), and LDL-C were not significantly affected by the three diets despite manipulation of these key fatty acids. However, both CAN (low saturates [SATs], high monounsaturates [MONOs]) and POL (high SATs, low polyunsaturates [POLYs]) depressed HDL-C significantly (−8 mg/dL) relative to the AHA (mod SATs, mod POLYs) diet. Consequently, the AHA diet increased HDL
3-C and lowered the LDL/HDL 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 consuming a moderate fat load (<31% en) low in myristic acid (14:0) and dietary cholesterol, the effect of palmitic acid (16:0) on TC and the LDL/HDL ratio is comparable to that of monounsaturated oleic acid (18:1), Furthermore, a definite intake of POLYs and SATs may be essential for maximizing HDL
3-C under these conditions.