VARYING DIETARY-FAT TYPE OF REDUCED-FAT DIETS HAS LITTLE EFFECT ON THE SUSCEPTIBILITY OF LDL TO OXIDATIVE MODIFICATION IN MODERATELY HYPERCHOLESTEROLEMIC SUBJECTS

The effect of the fatty acid composition of reduced-fat diets on the i n vitro oxidation of LDL was examined in 14 moderately hypercholestero lemic [low density lipoprotein (LDL) > 3.36 mmol/L] postmenopausal fem ale and male subjects (age 44-78 y), Each subject consumed each of fiv e reduced-fat diets [30 energy percent (E%) fat, 17 E% protein and 53 E% carbohydrate] enriched in beef tallow, canola oil, corn oil, olive oil or rice bran oil (20 E%) for 32-d periods. In vitro oxidation of L DL was assessed by incubating LDL with hemin and hydrogen peroxide, an d measuring the time required for the reaction to reach maximum veloci ty (lag time). LDL lag times were 93.2 +/- 25.8, 95.9 +/- 26.4, 104.2 +/- 32.7, 108.0 +/- 26.6 and 113.1 +/- 24.0 min for corn oil, beef tal low, rice bran oil, canola oil and olive oil periods, respectively. Wh en the data from all dietary phases were pooled, LDL alpha-tocopherol level (r = 0.30, P = 0.01) and plasma 18:1/18:2 ratio (r = 0.22, P = 0 .08) were positively related to resistance of LDL to oxidation, Differ ences induced by the dietary perturbations in LDL content of beta-cryp toxanthin, lutein/zeaxanthin, lycopene, alpha-carotene or beta-caroten e, and LDL particle size were not related to resistance of LDL to oxid ation, In conclusion, in middle-aged and elderly moderately hyperchole sterolemic subjects, the consumption of reduced-fat diets enriched in animal fat or vegetable oils with a relatively wide range of fatty aci d profiles did not alter the in vitro susceptibility of LDL to oxidati on. The advantages of reducing the saturated fat content of the diet w ere reflected in lower total and LDL cholesterol levels.