Effects of low-to-moderate alcohol supplementation on urinary estrogen metabolites in postmenopausal women in a controlled feeding study.

Heavy alcohol drinking is associated with increased breast cancer risk, but associations with low-to-moderate alcohol consumption are less clear and the biological mechanisms are not well defined. The objective of this study was to evaluate the effects of 8 weeks of low (15 g/d) and moderate (30 g/d) alcohol ingestion on concentrations of 15 urinary estrogen metabolites (EMs) in postmenopausal women (n = 51) in a controlled feeding study with a randomized crossover design. Compared to no alcohol, 15 g/day for 8 weeks had no effect on urinary EMs. However, compared to no alcohol, 30 g/day for 8 weeks decreased urinary 2-hydroestrone (2-OHE1) by 3.3% (P = 0.055) and increased 16-epiestriol (16-EpiE3) by 26.6% (P = 0.037). Trends for reduced urinary 2-OHE1 (P = 0.045), reduced ratio of 2-OH:16OH pathways (P = 0.008), and increased 16-EpiE3 (P = 0.035) were observed as alcohol ingestion increased from 0 g to 15 g to 30 g/d. Moderate alcohol consumption for 8 weeks had modest effects on urinary concentrations of 2-OHE1 and 16-EpiE3 among postmenopausal women in a carefully controlled feeding study.