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Diabetic Medicine

Year: 2011  |  Volume: 28  |  Issue: 7  |  Page No.: 805 - 810

High oolong tea consumption predicts future risk of diabetes among Japanese male workers: a prospective cohort study

Y. Hayashino, S. Fukuhara, T. Okamura, T. Tanaka and H. Ueshima

Abstract

Aims  Acute administration of oolong tea decreases blood glucose levels. We investigated the association between long-term oolong tea intake and subsequent risk of developing diabetes among men of working age.

Methods  Data were analysed from a cohort of participants in the High-risk and Population Strategy for Occupational Health Promotion Study (HIPOP-OHP), conducted in Japan from 1999 to 2004. Oolong tea intake at baseline and subsequent risk of diabetes was evaluated using a Cox proportional hazards model.

Results  Of 4975 male workers, a total of 201 cases of diabetes were reported over a median of 3.4 years of follow-up. Mean age and BMI of all participants at baseline were 38.3 years and 22.9 kg/m2, respectively. Compared with those not consuming oolong tea, multivariable adjusted hazard ratios for developing diabetes were 1.00 (95% CI 0.67-1.49) for those who drank one cup of oolong tea per day and 1.64 (95% CI 1.11-2.40) for those drinking two or more cups per day. Fasting blood glucose increment per year was 0.11 mmol/l (95% CI 0.09-0.12 mmol/l), 0.12 mmol/l (95% CI 0.09-0.15 mmol/l) and 0.15 mmol/l (95% CI 0.11-0.18 mmol/l), respectively, for oolong tea consumption of 0, 1 and ≥ 2 cups/day, with a significant linear trend (P < 0.0001).

Conclusions  Long-term consumption of oolong tea may be a predictive factor for new onset diabetes. Further studies are necessary to elucidate the role of oolong tea in the risk of developing diabetes.

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