Dietary fat intake and endogenous sex steroid hormone levels in postmenopausal women

Purpose: To examine the relationship between plasma levels of reproductive sex steroid hormones in postmenopausal women and their reported fat intake. Methods: We measured plasma sex steroid hormones levels in plasma collected in 1989 and 1990 from 381 healthy postmenopausal women. For each woman, we measured fat intake in 1986 and 1990 by a food-frequency questionnaire. Th e cross-sectional associations between the percentage of energy from total and specific types of dietary fat intake and plasma hormone levels were ass essed by linear regression, controlling for energy intake, obesity, and pro tein intake. Results: The plasma estradiol level was 4.3% lower (95% confidence limits, -8.3%, -0.2%) for ct substitution of 5% of energy from fat intake for an eq uivalent amount of energy from carbohydrate when adjusted for obesity and o ther covariates. Estradiol was also inversely associated with all other fel t types except trans fat; the inverse associations with vegetable fat and m arine omega-3 felts were statistically significant. Conclusion: We observed an inverse association between total fat intake ave raged over 4 to 5 years and estradiol levels. This result is inconsistent w ith the hypothesis that fat intake predisposes to breast cancer risk by rai sing endogenous estrogen levels. (C) 2000 by American Society of Clinical O ncology.