Additive effects of green tea and coffee on all-cause mortality in patients with type 2 diabetes mellitus: the Fukuoka Diabetes Registry

Abstract

Introduction: The impact of consuming green tea or coffee on mortality in patients with diabetes is controversial. We prospectively investigated the impact of each beverage and their combination on mortality among Japanese patients with type 2 diabetes.

Research design and methods: In all, 4923 patients (2790 men, 2133 women) with type 2 diabetes (mean age, 66 years) were followed prospectively (median, 5.3 years; follow-up rate, 99.5%). We evaluated the amount of green tea and coffee consumed using self-administered questionnaires.

Results: During the follow-up period, 309 participants died. The consumption of green tea, coffee, and a combination of the beverages was associated with reduced all-cause mortality. Multivariable-adjusted hazard ratios (95% CIs) for green tea were as follows: none 1.0 (referent); 0.85 (0.60-1.22) for ≤1 cup/day; 0.73 (0.51-1.03) for 2-3 cups/day; 0.60 (0.42-0.85) for ≥4 cups/day; and P for trend, 0.002. For coffee, they were: none 1.0 (referent); 0.88 (0.66-1.18) for <1 cup/day; 0.81 (0.58-1.13) for 1 cup/day; 0.59 (0.42-0.82) for ≥2 cups/day; P for trend, 0.002. With the combination they were 1.0 (referent) for no consumption of green tea and coffee; 0.49 (0.24-0.99) for 2-3 cups/day of green tea with ≥2 cups/day of coffee; 0.42 (0.20-0.88) for ≥4 cups/day of green tea with 1 cup/day of coffee; and 0.37 (0.18-0.77) for ≥4 cups/day of green tea with ≥2 cups/day of coffee.

Conclusions: Higher consumption of green tea and coffee was associated with reduced all-cause mortality: their combined effect appeared to be additive in patients with type 2 diabetes.

Keywords: green tea catechin; mortality; nutritional epidemiology; type 2 diabetes.

Figure 1

Combined effects of green tea and coffee consumption on all-cause mortality in patients with type 2 diabetes. The estimates are adjusted for age, sex, BMI, diabetes duration, current smoking habit, current alcohol intake, LTPA, sleep duration, HbA_1c, UACR, systolic blood pressure, LDL cholesterol, history of CVD and cancer. *P<0.05 vs the reference group (NO consumption of green tea and coffee). BMI, body mass index; CVD, cardiovascular disease; HbA_1c, hemoglobin A_1c; LDL, low-density lipoprotein; LTPA, leisure-time physical activity; UACR, urinary albumin creatinine ratio.