Ascorbic Acid Supplements and Kidney Stones Incidence Among Men and Women: A systematic review and meta-analysis.

The relationship of ascorbic acid (AA) supplements and risk of kidney stones among men and women is controversial. This systematic evaluation was performed to obtain comprehensive evidence about the relationship of AA supplements and risk of kidney stones among men and women. A systematic search of Pubmed, the Cochrane Library, Web of Science, Embase was performed to identify studies that exhibited the relationship of AA supplements and risk of kidney stones among men and women were published up to Mar 2017. Outcomes of interest included kidney stones incidence and risk factors. Four studies estimating the association between AA supplements and risk of kidney stones were included for meta-analysis. The kidney stones incidence was significantly higher in men than women with AA supplements (OR= 1.62; 95% CI: 1.09 to 2.42; P=0.02). AA supplements (250-499mg/d, 1000-1499mg/d) was remarkably correlated with the risk of renal stones among men (OR= 1.14, 95% CI: 1.00 to 1.28, P=0.04; OR= 1.12, 95% CI: 1.11 to 1.13, P<0.00001; respectively). However, AA supplements (500-999 mg/d, >1500 mg/d) did not correlate with the risk of renal stones among men (OR= 1.20, 95% CI: 0.99 to 1.46, P=0.06; OR= 1.28, 95% CI: 1.00 to 1.63, P= 0.05; respectively). In addition, AA supplements (250-499mg/d, 500-999mg/d, 1000-1499mg/d, >1500mg/d) did not remarkably correlate with the risk of renal stones among women (OR= 1.00, 95% CI: 0.82 to 1.22, P=0.98; OR= 1.08, 95% CI: 0.99 to 1.18, P=0.09; OR= 0.99, 95% CI: 0.90 to 1.08, P=0.77; OR= 0.99, 95% CI: 0.99 to 1.09, P=0.88; respectively). AA supplements was remarkably correlated with higher risk for kidney stones incidence in men, but not in women. Further multicenter, prospective and long-term follow-up RCTs are required to verify these findings.