Total, Dietary, and Supplemental Vitamin C Intake and Risk of Incident Kidney Stones

Ferraro PM, Curhan GC, Gambaro G, Taylor EN

Published in American Journal of Kidney Diseases

Methodology

Pooled prospective cohort analysis of the Health Professionals Follow-up Study and Nurses' Health Studies I and II, with repeated food-frequency questionnaires and multivariable-adjusted Cox models for incident symptomatic kidney stones.

Key Findings

Across three large prospective cohorts (197,271 participants; 6,245 incident stones), higher total and dietary vitamin C intake was not associated with kidney stone risk in women, but supplemental vitamin C of 1,000 mg/day or more was associated with a significantly increased risk in men (hazard ratio about 1.43 versus no supplement use).

Conclusions

Dietary vitamin C appears safe, but high-dose vitamin C supplements are associated with a meaningfully increased risk of kidney stones in men and should be avoided by stone formers.

Limitations

Observational design cannot prove causation and residual confounding by fluid intake and other supplement use is possible; intake self-reported via food-frequency questionnaires; too few high-dose users among women to exclude an effect in women.