Consumption of caffeinated beverages and serum concentrations of sex steroid hormones in US men.

Background: By modulating the levels of sex steroid hormones and sex hormone-binding globulin (SHBG), caffeine could be a factor in the development of several conditions in men, including prostate cancer. The aim of this study was to evaluate if caffeine consumption is associated with concentrations of sex steroid hormones and SHBG in men.
Methods: 1,410 men aged 20 + years who attended the morning examination session of the Third National Health and Nutrition Examination Survey (1988-1991) were included in the analysis. Coffee and soft drink consumption was assessed using a food frequency questionnaire. Daily caffeine intake was estimated by multiplying caffeine content per cup times the daily frequency of coffee, tea, or soft drink consumption. Serum levels of hormones and SHBG were measured by immunoassay. Associations of frequency of beverage consumption or estimated caffeine intake with hormone levels were examined using multivariable linear regression.
Results: Coffee consumption was positively associated with SHBG concentration (p = 0.045) taking lifestyle factors into account, but mutually adjusting for testosterone and estradiol attenuated the association; no association with SHBG was observed for soft drink consumption or caffeine intake. No associations between caffeinated beverage consumption and androgen or estrogen concentrations were observed.
Conclusion: Men who drink coffee more frequently may have higher circulating SHBG concentration, but there were no consistent associations for soft drinks or caffeine intake.