Studies of women eating diets with different fatty acid composition. I. Plasma lipoproteins and steroid excretion.

Moderate changes in dietary fat composition have been recommended to improve plasma cholesterol status. Such changes have not been studied extensively in women. This research evaluates plasma lipoprotein and steroid excretion changes in young women who consumed a diet similar to US average consumption in 1974 [40 en% fat, polyunsaturated (P) to saturated fatty acid (S) ratio, P/S = 0.3, US74] or a diet modified to contain 30 en% fat, P/S = 1.0 (MOD). Following a preexperimental period of self-selected diets, young women were fed the diets for 28-day periods in a crossover design with 10 women at the University of Nebraska, Lincoln, and 10 at Iowa State University, Ames. Plasma lipoproteins and steroid excretion were quantitated and the compositions determined. Data were analyzed for race (five Chinese, 14 Caucasians) and for diet carryover effects, as well as for primary diet effects. In the Chinese women, the US74 diet raised total and very-low-density lipoprotein (VLDL) cholesterol compared to prior self-selected or modified diets; in the Caucasian women the MOD diet lowered total, low-density lipoprotein (LDL), and VLDL cholesterol. The diet carryover was evident in total high-density lipoprotein (HDL) and HDL3 cholesterol. Total HDL and HDL3 cholesterol in response to the US74 diet were unchanged from the MOD diet when the US74 diet followed the MOD diet, but were lower than modified when the US74 diet followed self-selected diets. The US74 diet resulted in greater neutral sterol excretion than the MOD diet; this response was more marked in the self-selected, US74, MOD sequence than in the self-selected, MOD, US74 sequence.(ABSTRACT TRUNCATED AT 250 WORDS)