Coffee and Caffeine Consumption in Relation to Sex Hormone-Binding Globulin and Risk of Type 2 Diabetes in Postmenopausal Women

  1. Simin Liu, MD, ScD (siminliu{at},3,4
  1. 1. Department of Epidemiology, Program on Genomics and Nutrition and the Center for Metabolic Disease Prevention, UCLA School of Public Health, Los Angeles, CA
  2. 2. Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA
  3. 3. Department of Medicine, UCLA David Geffen School of Medicine, Los Angeles, CA
  4. 4. Jonsson Comprehensive Cancer Center, UCLA, Los Angeles, CA


Objective: Coffee consumption has been inversely associated with type 2 diabetes risk, but its mechanisms are largely unknown. We aimed to examine whether plasma levels of sex hormones and sex hormone-binding globulin (SHBG) may account for the inverse association between coffee consumption and type 2 diabetes risk.

Research Design and Methods: We conducted a case-control study nested in the prospective Women's Health Study. During a median followup of 10 years, 359 postmenopausal women with newly diagnosed type 2 diabetes were matched with 359 controls by age, race, duration of follow-up, and time of blood draw.

Results: Caffeinated-coffee was positively associated with SHBG but not with sex hormones. Multivariable-adjusted geometric mean levels of SHBG were 26.6 nmol/L among women consuming ≥4 cups/day of caffeinated-coffee and 23.0 nmol/L among non-drinkers (P for trend = 0.01). In contrast, neither decaffeinated-coffee nor tea was associated with SHBG or sex hormones. Multivariable-adjusted odds ratio (OR) of type 2 diabetes for women consuming ≥4 cups/day of caffeinated-coffee compared with non-drinkers was 0.47 (95% CI, 0.23 – 0.94; P for trend = 0.047). The association was largely attenuated after further adjusting for SHBG (OR=0.71; 95% CI, 0.31 – 1.61; P for trend = 0.47). In addition, carriers of rs6259 minor allele and non-carriers of rs6257 minor allele of SHBG gene consuming ≥2 cups/day of caffeinated-coffee had lower risk of type 2 diabetes in directions corresponding to their associated SHBG.

Conclusions: Our findings suggest that SHBG may account for the inverse association between coffee consumption and type 2 diabetes risk among postmenopausal women.

  • Received August 22, 2010.
  • Accepted October 20, 2010.
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