Vitamin C intake,circulating vitamin C and risk of stroke: a meta-analysis of prospective studies.

Though vitamin c supplementation has shown no observed effects on stroke prevention in several clinical trials,uncertainty remains as to whether long-term,low-dose intake influences the development of stroke among general populations. furthermore,the association between circulating vitamin c and the risk of stroke is also unclear. for further clarification of these issues,we conducted a meta-analysis of prospective studies. pubmed and embase databases were searched,and the bibliographies of the retrieved articles were also reviewed to identify eligible studies. summary relative risk (rrs) with corresponding 95% confidence intervals (cis) were computed with a random-effects model. the summary rr for the high-versus-low categories was 0.81 (95% ci: 0.74 to 0.90) for dietary vitamin c intake (11 studies),and 0.62 (95% ci: 0.49 to 0.79) for circulating vitamin c (6 studies). the summary rr for each 100 mg/day increment in dietary vitamin c was 0.83 (95% ci: 0.75 to 0.93) (10 studies),and for each 20 μmol/l increment in circulating vitamin c was 0.81 (95% ci: 0.75 to 0.88) (5 studies). few studies reported results for vitamin c supplements (rr for high-versus-low intake=0.83,95% ci: 0.62 to 1.10,3 studies). this meta-analysis suggests significant inverse relationships between dietary vitamin c intake,circulating vitamin c,and risk of stroke.