Dietary zinc intake and kidney stone formation: evaluation of NHANES III.

AIMS We aimed to determine whether there is an association between dietary zinc intake (DZI) and prevalent kidney stone disease defined as self-report of any previous episode of kidney stone. METHODS We examined The Third National Health and Nutrition Examination Survey (NHANES III), a large US population-based cross-sectional study, and used logistic regression analyses to determine the independent association between DZI and prevalent kidney stone disease. RESULTS A total of 15,444 men and women over 18 years of age were eligible for analysis. Among them, 710 participants reported a history of kidney stones. Stone formers tended to have higher DZI than non-stone formers among NHANES III participants, though this difference did not reach statistical significance (p = 0.1). Multivariate adjusted logistic regression analysis revealed that higher DZI (log transformed) was associated with a significantly increased risk of kidney stone disease (odds ratio, OR = 1.41, 95% confidence interval, CI: 1.10-1.81, p = 0.01). After categorizing zinc intake into three groups, those with highest DZI (>15 mg/day) were also associated with a significantly increased risk of kidney stone disease, compared to those with lower DZI (<7 mg/day; OR = 1.70, 95% CI: 1.13-2.57, p = 0.01). CONCLUSIONS Our study suggests that higher DZI is associated with increased risk of kidney stone disease. Future prospective studies are needed to clarify the causal relationship between zinc intake and kidney stone formation.