Supplementing with vitamin C showed a statistically significant increase in kidney stone risk, but the clinical significance is negligible.

“Another perspective cohort study in more than 48,000 Swedish men found that the men's risk of developing kidney stones was 0.16 percent per year among men who did not supplement but was 0.3 percent per year among those who did which is a statistical difference with no clinical significance in other words a person in this study who supplemented with vitamin C can expect a kidney stone every 323 years whereas a person who did not supplement with vitamin C can expect a kidney stone every 613 years”