Dietary factors and the risk of incident kidney stones in men: new insights after 14 years of follow-up.
Level 3 - non-randomized controlled study
Prospective cohort study
PubMed 15579526 · doi:10.1097/01.ASN.0000146012.44570.20
What was done
A prospective cohort study tracked 45,619 men with no prior history of nephrolithiasis over 14 years (477,700 person-years of follow-up). Dietary intake was assessed every 4 years using self-administered food frequency questionnaires. The primary outcome was incident, symptomatic kidney stones, with 1,473 cases documented.
What was found
Dietary calcium in men under 60 years was associated with lower risk for highest versus lowest quintile (multivariate RR 0.69, 95% CI 0.56 to 0.87, P = 0.01 for trend), with no association in men aged 60 or older. Total vitamin C intake of 1000 mg/d or greater versus less than 90 mg/d was associated with increased risk (multivariate RR 1.41, 95% CI 1.11 to 1.80, P = 0.01 for trend). Highest versus lowest quintile comparisons showed reduced risk for magnesium (RR 0.71, 95% CI 0.56 to 0.89, P = 0.01), potassium (RR 0.54, 95% CI 0.42 to 0.68, P < 0.001), and fluid (RR 0.71, 95% CI 0.59 to 0.85, P < 0.001). Animal protein intake was associated with higher risk only in men with BMI <25 kg/m2 (RR 1.38, 95% CI 1.05 to 1.81, P = 0.03). Sodium, phosphorus, sucrose, phytate, vitamin B6, vitamin D, and supplemental calcium showed no independent association.
Why it matters
This study shows that dietary influences on nephrolithiasis risk vary by patient age and BMI, suggesting that dietary guidance for stone prevention should be tailored rather than uniform.
Limits
The observational design cannot establish causality. Dietary exposure was self-reported via food frequency questionnaires every 4 years, introducing potential misclassification. The study included only men, stone composition was not reported, and residual confounding remains possible.
Cited by
- contradicts Two large prospective cohort studies found an association between high vitamin C intake and increased relative risk of kidney stones in multivariate analysis, but found no statistically significant association on univariate analysis.