Caffeine, Coffee, and Tea Intake and Urinary Estrogens and Estrogen Metabolites in Premenopausal Women

Background: Prior studies have found weak inverse associations between breast cancer and caffeine and coffee intake, possibly mediated through their effects on sex hormones. Methods: High-performance liquid chromatography/tandem mass spectrometry was used to quantify levels of 15 individual estrogens and estrogen metabolites (EM) among 587 premenopausal women in the Nurses' Health Study II with mid-luteal phase urine samples and caffeine, coffee, and/or tea intakes from self-reported food frequency questionnaires. Multivariate linear mixed models were used to estimate geometric means of individual EM, pathways, and ratios by intake categories, and P values for tests of linear trend. Results: Compared with women in the lowest quartile of caffeine consumption, those in the top quartile had higher urinary concentrations of 16 alpha-hydroxyestrone (28% difference; P-trend = 0.01) and 16-epiestriol (13% difference; P-trend = 0.04), and a decreased parent estrogens/2-, 4-, 16-pathway ratio (P-trend = 0.03). Coffee intake was associated with higher 2-catechols, including 2-hydroxyestradiol (57% difference, >= 4 cups/day vs. <= 6 cups/week; P-trend = 0.001) and 2-hydroxyestrone (52% difference; P-trend = 0.001), and several ratio measures. Decaffeinated coffee was not associated with 2-pathway metabolism, but women in the highest (vs. lowest) category of intake (>= 2 cups/day vs. <= 1-3 cups/month) had significantly lower levels of two 16-pathway metabolites, estriol (25% difference; P-trend = 0.01) and 17-epiestriol (48% difference; P-trend = 0.0004). Tea intake was positively associated with 17-epiestriol (52% difference; P-trend = 0.01). Conclusion: Caffeine and coffee intake were both associated with profiles of estrogen metabolism in premenopausal women. Impact: Consumption of caffeine and coffee may alter patterns of premenopausal estrogen metabolism. (C) 2015 AACR.