Chronic Fructose and Sucrose Intake and 24-Hour Urine Composition

Background Consumption of sugar, including fructose and sucrose, is associated with higher risk of kidney stones. The association is believed to be because of an acute rise in urine calcium after sugar intake. However, the association between chronic sugar intake and urine composition is not known. Methods We conducted a cross-sectional analysis of dietary intake from a food frequency questionnaire and 24-hour urine collections from 6457 kidney stone- and non-stone-former participants from the Nurses' Health Study I (1,297), Nurses' Health Study II (4,053), and Health Professionals Follow-up Study (1,107). We used multivariate adjusted linear regression to examine the association between long-term intake of free fructose, total fructose, and sucrose and 24-hour urine composition. Results Higher free and total fructose and sucrose intakes were each associated with lower 24-hour urine calcium. Comparing the highest versus lowest quintiles, mean urine calcium was 23 (31-15) mg/d lower for free fructose (P-trend <0.001), 26 (34-18) mg/d for total fructose (P-trend <0.001), and 8 (17-1) mg/d for sucrose (P-trend 0.03). Higher total fructose intake was associated with slightly higher calcium phosphate supersaturation (P-trend 0.002), and higher sucrose intake was associated with higher calcium oxalate (P-trend 0.03) and calcium phosphate (P-trend <0.001) supersaturations. Differences in 24-hour urine calcium were similar between kidney stone- and non-stone-former participants. Conclusions In contrast to the acute rise in urine calcium previously seen in short-term studies, higher long-term intake of free and total fructose and sucrose was associated with lower 24-hour urine calcium excretion in those with and without a history of kidney stones. Other modest differences in urine composition were noted for each sugar. Future studies should test potential mechanisms for the observed lower 24-hour urine calcium with chronic sugar intake.