Fructose consumption and the risk of kidney stones.

Fructose consumption has markedly increased over the past decades. This intake may increase the urinary excretion of calcium, oxalate, uric acid, and other factors associated with kidney stone risk. We prospectively examined the relationship between fructose intake and incident kidney stones in the Nurses' Health Study I (NHS I) (93,730 older women), the Nurses' Health Study II (NHS II) (101,824 younger women), and the Health Professionals Follow-up Study (45,984 men). Food frequency questionnaires were used to assess free fructose and sucrose intake every 4 years. Total-fructose intake was calculated as free fructose plus half the intake of sucrose, and expressed as percentage of total energy. Cox proportional hazard regressions were adjusted for age, body mass index (BMI), thiazide use, caloric intake, and other dietary factors. We documented 4902 incident kidney stones during a combined 48 years of follow-up. The multivariate relative risks of kidney stones significantly increased for participants in the highest compared to the lowest quintile of total-fructose intake for all three study groups. Free-fructose intake was also associated with increased risk. Non-fructose carbohydrates were not associated with increased risk in any cohort. Our study suggests that fructose intake is independently associated with an increased risk of incident kidney stones.