Vitamin C Intake, Circulating Vitamin C and Risk of Stroke: A Meta‐Analysis of Prospective Studies

Abstract

BackgroundThough 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.Methods and ResultsPubMed 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).ConclusionsThis meta‐analysis suggests significant inverse relationships between dietary vitamin C intake, circulating vitamin C, and risk of stroke.

Diet and Stroke

“…Similarly, another meta-analysis of five prospective studies found that each 20 μmol/L of circulating vitamin C was associated with a 19% reduction in stroke risk; however only dietary vitamin C intake, not supplemental intake, had a statistically significant inverse association with stroke risk 28, 29 . This suggests that some micronutrients have stronger associations with reduced stroke risk when obtained from dietary, rather than supplemental sources.…”

“…Supplements administered at different stages of stroke risk factor development may have different effects 28 . Additionally, the effect of micronutrient supplementation on stroke risk among micronutrient deficient populations has not been well examined in meta-analyses and it is possible that correcting overt micronutrient deficiency would have a differential association with stroke risk compared than what has been observed in populations that are micronutrient replete 28, 29 . Additional studies are needed to further elucidate mechanisms through which micronutrient supplementation may reduce stroke risk in all populations before recommendations on specific micronutrients are warranted.…”

Redox signalling and cardioprotection: translatability and mechanism

“…Moreover, p.o. administration of vitamin C (Chen et al ., ) or the effects of combined vitamins C and E, through infusion and capsules (Jaxa‐Chamiec et al ., ; Lee et al ., ; Cook et al ., ), did not demonstrate a major effect of these antioxidant treatments on the clinical outcome of patients. Nevertheless, in diabetic patients, a reduction in 30 day cardiac mortality has been reported (Jaxa‐Chamiec et al ., ).…”

Overview of Meta-Analyses: The Impact of Lifestyle on Stroke Risk

“…The meta-analysis of Chen et al concerned vitamin C intake [48]. Consumption of high doses is preventive in the development of ischemic or hemorrhagic stroke (RR= 0.81; 0.74-0.90).…”