Vitamin Supplementation and Stroke Prevention
It is said that we are what we eat. It is advertised that vitamin supplements, of one kind or another, may invigorate us, our lives, and our health. Advertising has been so effective that in the year 2000, more than half of the adult population in the United States was taking dietary vitamin supplements.1 This review examines the evidence linking vitamin supplementation with the incidence and prevention of stroke.
Search Strategy and Selection Criteria
References for this review were identified by searches of the PubMed database from 1970 until February 2012 using the following search terms: vitamins, antioxidants, folic acid, B-vitamins, vitamin C, vitamin D, vitamin E, diet, nutrition, stroke, prospective cohort study, randomized controlled trial (RCT), systematic review, and meta-analysis. Articles were also identified through searches of reference lists and my own files. Studies were selected for inclusion on the basis of a judgment about the quality of the evidence according to 4 key elements: study design, study quality, consistency, and directness, as proposed by the Grading of Recommendations Assessment, Development and Evaluating (GRADE) working group (www.gradeworkinggroup.org).2,3 For each vitamin, the studies with the highest level of evidence based on the GRADE criteria2 were included. Only articles published in English were included.
The oxidative modification hypothesis of atherosclerosis is that oxidation of low-density lipoprotein cholesterol (lipid peroxidation) allows it to accumulate in artery walls and promote atherosclerosis.4 This has prompted several studies of the effect of reducing oxidative stress by means of antioxidant vitamins (beta-carotene; vitamins A, C, and E) in preventing stroke.
Vitamin A and Beta-Carotene
Beta-carotene is a fat-soluble antioxidant and the biologically active metabolite of vitamin A.
A meta-analysis of 3 randomized controlled trials (RCTs) of beta-carotene in a total of 82 483 participants showed no effect of beta-carotene on the rate of stroke compared with control (OR, …