Abstract
BackgroundFindings from observational studies suggest that sex hormone-binding globulin (SHBG) and endogenous sex hormones may be mediators of the putative relation between coffee consumption and lower risk of type 2 diabetes. The objective of this study was to evaluate the effects of caffeinated and decaffeinated coffee on SHBG and sex hormone levels.FindingsAfter a two-week run-in phase with caffeine abstention, we conducted an 8-week parallel-arm randomized controlled trial. Healthy adults (n = 42) were recruited from the Boston community who were regular coffee consumers, nonsmokers, and overweight. Participants were randomized to five 6-ounce cups of caffeinated or decaffeinated instant coffee or water (control group) per day consumed with each meal, mid-morning, and mid-afternoon. The main outcome measures were SHBG and sex hormones [i.e., testosterone, estradiol, dehydroepiandrosterone sulfate].No significant differences were found between treatment groups for any of the studied outcomes at week 8. At 4 weeks, decaffeinated coffee was associated with a borderline significant increase in SHBG in women, but not in men. At week 4, we also observed several differences in hormone concentrations between the treatment groups. Among men, consumption of caffeinated coffee increased total testosterone and decreased total and free estradiol. Among women, decaffeinated coffee decreased total and free testosterone and caffeinated coffee decreased total testosterone.ConclusionsOur data do not indicate a consistent effect of caffeinated coffee consumption on SHBG in men or women, however results should be interpreted with caution given the small sample size. This is the first randomized trial investigating the effects of caffeinated and decaffeinated coffee on SHBG and sex hormones and our findings necessitate further examination in a larger intervention trial.
Highlights
Coffee consumption has been consistently associated with a lower risk of type 2 diabetes (T2DM), but the underlying mechanisms remain unclear
Our data do not indicate a consistent effect of caffeinated coffee consumption on sex hormone-binding globulin (SHBG) in men or women, results should be interpreted with caution given the small sample size
Caffeinated coffee consumption has been found to be associated with higher SHBG levels in data from cross-sectional studies in women [2,6,7,8]
Summary
Coffee consumption has been consistently associated with a lower risk of type 2 diabetes (T2DM), but the underlying mechanisms remain unclear. Data from observational studies suggest that sex hormone-binding globulin (SHBG) and endogenous sex hormones may modulate glycemia and risk of T2DM in men and women [1,2,3,4,5]. Caffeinated coffee consumption has been found to be associated with higher SHBG levels in data from cross-sectional studies in women [2,6,7,8]. We conducted an 8-week parallel-arm randomized trial to determine the effects of caffeinated and decaffeinated coffee on risk factors for T2DM. Findings from observational studies suggest that sex hormone-binding globulin (SHBG) and endogenous sex hormones may be mediators of the putative relation between coffee consumption and lower risk of type 2 diabetes. The objective of this study was to evaluate the effects of caffeinated and decaffeinated coffee on SHBG and sex hormone levels
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