Hydrogenated fat consumption affects cholesterol synthesis in moderately hypercholesterolemic women

To determine mechanisms by which hydrogenated fat influences plasma lipid l evels, 14 women (65-71 yrs with LDL-C greater than or equal to 130 mg.dl(-1 )) consumed, for 5-week periods each, a baseline (BL) diet (39% kcal fat, 1 64 mg chol.1000 kcal(-1)) and reduced fat diets (30% kcal) where two-thirds of the fat was either soybean oil (SO), low trans squeeze (SQM), medium tr ans tub (TM), or high trans stick (SM) margarines, or butter (BT), Plasma l ipid levels were analyzed at the end of each phase. Fractional synthesis ra tes (FSR) in pools/day (p.d(-1)) and absolute synthesis rates (ASR) in gram s/day (g.d(-1)) of free cholesterol (FC) were measured using the deuterium incorporation methodology, Plasma total (P < 0.01) and low density lipoprot ein (P < 0.05) cholesterol levels increased with increasing degree of hydro genation or saturated fat intake. High density lipoprotein cholesterol leve ls (P < 0.05) were lowest on the SM diet when compared to the BT diet. Low trans SQM (0.081 +/- 0.019 p d(-1)) and medium trans TM (0.086 +/- 0.029 p. d(-1)) diets elicited responses similar to the SO (0.078 +/- 0.024 p.d(-1)) diet, whereas high trans SM (0.053 +/- 0.029 p.d(-1)) diet mimicked the BT (0.062 +/- 0.017 p.d(-1)) and high fat BL (0.053 +/- 0.023 p.d(-1)) diet i n its suppression (P < 0.05) of FSR-FC. ASR-FC, which is an approximation o f the daily production of newly synthesized cholesterol, showed a trend sim ilar to the FSR-FC data. These results indicate that reduced synthesis is n ot responsible for the higher plasma TC levels seen with consumption of the SM, BT, and BL diets, and suggest that another mechanism, possibly impairm ent of the catabolic pathway of cholesterol, is involved. Hydrogenated fat consumption affects cholesterol synthesis in moderately hypercholesterolemi c women.