Objectives
To investigate the association between green tea intake and incident stones in two large prospective cohorts.
Methods
We examined self‐reported incident kidney stone risk in the Shanghai Men's Health Study (n = 58 054; baseline age 40–74 years) and the Shanghai Women's Health Study (n = 69 166; baseline age 40–70 years). Information on the stone history and tea intake was collected by in‐person surveys. Multivariable Cox proportional hazards models were adjusted for baseline demographic variables, medical history and dietary intakes including non‐tea oxalate from a validated food frequency questionnaire.
Results
During 319 211 and 696 950 person‐years of follow up, respectively, 1202 men and 1451 women reported incident stones. Approximately two‐thirds of men and one‐quarter of women were tea drinkers at baseline, of whom green tea was the primary type consumed (95% in men, 88% in women). Tea drinkers (men: hazard ratio 0.78, 95% confidence interval 0.69–0.88; women: hazard ratio 0.8, 95% confidence interval 0.77–0.98) and specifically green tea drinkers (men: hazard ratio 0.78, 95% confidence interval 0.69–0.88; women: hazard ratio 0.84, 95% confidence interval 0.74–0.95) had lower incident risk than never/former drinkers. Compared with never/former drinkers, a stronger dose–response trend was observed for the amount of dried tea leaf consumed/month by men (hazard ratiohighest category 0.67, 95% confidence interval 0.56–0.80, Ptrend < 0.001) than by women (hazard ratiohighest category 0.87, 95% confidence interval 0.70–1.08, Ptrend = 0.041).
Conclusions
Green tea intake is associated with a lower risk of incident kidney stones, and the benefit is observed more strongly among men.