Total, Dietary, and Supplemental Vitamin C Intake and Risk of Incident Kidney Stones.
Level 3 - non-randomized controlled study
Prospective cohort study
PubMed 26463139 · doi:10.1053/j.ajkd.2015.09.005
What was done
Prospective cohort analysis of 156,735 women in the Nurses' Health Study I and II and 40,536 men in the Health Professionals Follow-up Study followed for a median of 11.3 to 11.7 years. Total, dietary, and supplemental vitamin C intakes were assessed using food-frequency questionnaires and evaluated for association with incident kidney stones after multivariable adjustment for age, body mass index, thiazide use, and dietary factors.
What was found
A total of 6,245 incident kidney stones occurred during follow-up. In men, higher total vitamin C intake was significantly associated with increased risk of kidney stones compared to <90 mg/d: HRs were 1.19 (95% CI, 0.99-1.46) for 90-249 mg/d, 1.15 (95% CI, 0.93-1.42) for 250-499 mg/d, 1.29 (95% CI, 1.04-1.60) for 500-999 mg/d, and 1.43 (95% CI, 1.15-1.79) for ≥1,000 mg/d (P for trend = 0.005). Supplemental vitamin C intake of ≥1,000 mg/d in men was also associated with increased risk (HR 1.19; 95% CI, 1.01-1.40; P for trend = 0.001). Total and supplemental vitamin C intake were not significantly associated with kidney stone risk in women. Dietary vitamin C intake alone was not associated with stone risk in men or women.
Why it matters
This study clarifies that high total and supplemental vitamin C intake is associated with elevated kidney stone risk specifically in men, while dietary intake and intake in women show no significant association.
Limits
Nutrient intakes were derived from self-reported food-frequency questionnaires, kidney stone composition was not available for all cases, and very few participants consumed dietary vitamin C in excess of 700 mg/d.
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.