<p><strong>PURPOSE: </strong>To determine the association between dietary zinc intake and incident calcium kidney stones and examine the relationship between dietary zinc intake and urinary zinc excretion among adolescents.</p>

<p><strong>MATERIAL AND METHODS: </strong>This study was a nested case-control study conducted within a large pediatric healthcare system. Three 24-hour dietary recalls and spot urine chemistries were obtained for 30 participants aged 12-18 years with a first idiopathic calcium-based kidney stone and 30 healthy controls, matched on age, sex, race, and month of enrollment. Conditional logistic regression models were used to estimate the odds ratio (OR) between daily zinc intake and incident calcium kidney stones, adjusting for dietary phytate, protein, calcium, sodium, and oxalate. Multivariable linear regression was used to estimate the association between dietary and urine zinc, adjusting for urine creatinine and dietary phytate and calcium.</p>

<p><strong>RESULTS: </strong>Cases had lower daily zinc intake (8.1mg) than controls (10mg; p=0.029). Daily zinc intake of boys and girls with calcium stones was 2mg and 1.2mg lower, respectively, than the daily intake of zinc recommended by the Institute of Medicine. There was a 13% lower odds of incident stones for every 1mg higher daily zinc intake (OR, 0.87; 95% CI, 0.75-0.99). There was an estimated 4.5μg/dL increase in urine zinc per 1mg increase in dietary zinc (p=0.009), with weak evidence of a smaller increase in urine zinc in cases than in controls (interaction p=0.08).</p>

<p><strong>CONCLUSIONS: </strong>Lower dietary zinc intake was independently associated with incident calcium nephrolithiasis in this population of adolescents.</p>