Influence of dietary fat on menstrual cycle and menses length.

Abstract

Menstrual cycle and menses lengths were determined in 31 healthy premenopausal women randomized into one of two sets of weight-maintaining diets, those with a ratio of polyunsaturated to saturated fatty acids (P/S ratio) of 1.0 and those with a P/S ratio of 0.3. After a baseline interval of one menstrual cycle, both groups were fed a high fat diet (40 per cent energy from fat) for four menstrual cycles per subject, followed by a similar interval on a low fat diet (20 per cent energy from fat). There was a significant increase of 1.3 d (P = 0.02) in the average menstrual cycle length and 0.5 d (P = 0.01) in menses length on the low fat diet. Although no significant differences were evident between the P/S groups, the effect of low fat on menstrual cycle and menses length was most pronounced in the P/S = 1.0 group.