Dietary intake of fiber, fruit and vegetables decreases the risk of incident kidney stones in women: a Women's Health Initiative report.

PURPOSE: We evaluated the relationship between dietary fiber, fruit and vegetable intake, and the risk of kidney stone formation.

MATERIALS AND METHODS: Overall 83,922 postmenopausal women from the Women's Health Initiative observational study were included in the analysis and followed prospectively. Cox proportional hazards regression analyses were used to evaluate the associations between total dietary fiber, fruit and vegetable intake, and the risk of incident kidney stone formation, adjusting for nephrolithiasis risk factors (age, race/ethnicity, geographic region, diabetes mellitus, calcium supplementation, hormone therapy use, body mass index and calibrated caloric intake; and dietary water, sodium, animal protein and calcium intake). Women with a history of kidney stones (3,471) were analyzed separately.

RESULTS: Mean age of the women was 64±7 years, 85% were white and 2,937 (3.5%) experienced a kidney stone in a median followup of 8 years. In women with no history of kidney stones higher total dietary fiber (6% to 26% decreased risk, p <0.001), greater fruit intake (12% to 25% decreased risk, p <0.001) and greater vegetable intake (9% to 22% decreased risk, p=0.002) were associated with a decreased risk of incident kidney stone formation in separate adjusted models. In women with a history of stones there were no significant protective effects of fiber, fruit or vegetable intake on the risk of kidney stone recurrence.

CONCLUSIONS: Greater dietary intake of fiber, fruits and vegetables was associated with a reduced risk of incident kidney stones in postmenopausal women. The protective effects were independent of other known risk factors for kidney stones. In contrast, there was no reduction in risk in women with a history of stones.