Increased amount and duration of tea consumption may be associated with decreased risk of renal stone disease

Purpose Previous studies have looked into the association between tea consumption and renal stone disease, but the impact of tea consumption over time has not yet been fully clarified. Our study aimed to examine the amount and duration of tea consumption concomitantly in relation to the risk of renal stone disease. Methods A total of 13,842 subjects who underwent health check-ups were recruited. Average tea consumption per day was defined as the amount of tea consumption per day multiplied by the frequency per week divided by seven. A cup was defined as 120mL for each Chinese traditional teapot, and cup-year was calculated by multiplying the number of daily cups and the years of tea consumption to express the cumulative dose of tea consumption over time. The diagnosis of renal stone disease was established based on the results of abdominal sonography. Results The amount of daily tea consumption was 119.2306.8 and 131.7 +/- 347.3mL in groups with and without renal stone disease. After adjusting for other clinical variables, daily tea consumption240mL vs. none was related to lower risk of renal stone disease (OR=0.84, CI 0.71-0.99, p=0.037). In another model, the associated risk of renal stone disease decreased significantly with tea consumption20 cup-year (OR=0.79, CI 0.66-0.94, p=0.008), but not <20 cup-year (OR=0.92, CI 0.78-1.09, p=0.34). Conclusions Daily tea consumption240mL (two cups) was associated with a lower risk of renal stone disease. Tea consumption >= 20 cup-year also had a decreased associated risk of renal stone disease.