The Effect of Vitamin C Supplements on Urinary Stone Risk: A Systematic Review and Meta-Analysis
Ala’a Farkouh, Evan Seibly, Matthew I. Buell, Daniel Jhang, Akin S. Amasyali, Zhamshid Okhunov, D. Duane BaldwinIntroduction and Objective:
With the increased intake of vitamin C supplements during the COVID pandemic, physicians have reported an increase in stone incidence and complexity. The purpose of this systematic review and meta-analysis was to study the effect of vitamin C supplements on urine parameters associated with stone formation.
Methods:
A comprehensive review was performed to retrieve relevant articles published from 1965 until February 2023. Studies were included if they were interventional studies investigating the effect of vitamin C supplements on 24-hour urinary parameters (oxalate, citrate, and calcium) in both stone formers (SFs) and nonstone formers (NSFs), compared with either baseline values or a placebo group. Meta-analyses were performed to calculate the mean difference (MD) measuring the effect of vitamin C supplements on these parameters.
Results:
The initial database search yielded 808 titles and after rigorous screening, nine studies were included. Pooled analysis revealed a significant increase in urinary oxalate after vitamin C supplementation compared with baseline (MD = 9.72 mg/24 h;
Conclusions:
Vitamin C supplements significantly increase urinary oxalate excretion in both SFs and NSFs. This may contribute to stone formation and may worsen stone presentation among those who consume these supplements.