Context: Low overnight urinary melatonin metabolite concentrations have been associated with increased risk for breast cancer among postmenopausal women. The Postmenopausal Women's Alcohol Study was a controlled feeding study to test the effects of low to moderate alcohol intake on potential risk factors for breast cancer including serum and urinary levels of hormones and other biomarkers. Previously, we observed significant increases in concentrations of serum estrone sulfate and dehydroepiandrosterone sulfate in participants after consumption of 15 or 30 g (one or two drinks) of alcohol per day.
Objective: In the present analysis, we evaluated the relationship of alcohol consumption with 24-h urinary 6-sulfatoxymelatonin (6-SMT) concentration (micrograms per 24 h).
Design and participants: Healthy postmenopausal women (n = 51) consumed a controlled diet plus each of three treatments (a nonalcoholic placebo beverage or 15 or 30 g alcohol/d) during three 8-wk periods in random order under conditions of weight maintenance.
Measures: 6-SMT was measured in 24-h urine samples that were collected at entry into the study (baseline) and at the midpoint (4 wk) and end (8 wk) of each of the three diet periods.
Results: Concentration of 6-SMT was not significantly modified by the alcohol treatment after adjustment for body mass index, hours of sleep, daylight hours, and baseline level of 6-SMT.
Conclusions: These results suggest that low to moderate daily alcohol consumption does not significantly affect 24-h urinary levels of melatonin among healthy postmenopausal women.