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Effect of vitamin C and vitamin E supplementation on endothelial function: a systematic review and meta-analysis of randomised controlled trials

Lookup NU author(s): Ammar Ashor, Dr Mario Siervo, Dr Jose Lara-Gallegos, Dr Clio Oggioni, Sorena Afshar, Professor John Mathers

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Abstract

Randomised controlled trials (RCT) testing the effects of antioxidant supplements on endothelial function (EF) have reported conflicting results. We aimed to investigate the effects of supplementation with antioxidant vitamins C and E on EF and to explore factors that may provide explanations for the inconsistent results. We searched four databases (MEDLINE, Embase, Cochrane Library and Scopus) from inception until May 2014 for RCT involving adult participants aged >= 18 years who were supplemented with vitamins C and E alone or in combination for more than 2 weeks and reporting changes in EF measured using flow mediated dilation or forearm blood flow. Data were pooled as standardised mean difference (SMD) and analysed using a random-effects model. Significant improvements in EF were observed in trials supplementing with vitamin C alone (500-2000 mg/d) (SMD: 0.25, 95% CI 0.02, 0.49, P = 0.043) and vitamin E alone (300-1800 IU/d; 1 IU vitamin E = 0.67 mg natural vitamin E) (SMD: 0.48, 95% CI 0.23, 0.72, P = 0.0001), whereas co-administration of both vitamins was ineffective (vitamin C: 500-2000 mg/d; vitamin E: 400-1200 IU/d) (SMD: 0.12, 95% CI -0.18, 0.42, P = 0.428). The effect of vitamin C supplementation on EF increased significantly with age (beta 0.023, 95% CI 0.001, 0.05, P = 0.042). There was a significant negative correlation between baseline plasma vitamin E concentration and the effect of vitamin E supplementation on EF (beta -0.03, 95% CI -0.06, -0.001, P = 0.029). Supplementation with either vitamin C or vitamin E alone improves EF. However, subgroup analysis emphasises the importance of careful characterisation and selection of a population group which may benefit from such supplementation.


Publication metadata

Author(s): Ashor AW, Siervo M, Lara J, Oggioni C, Afshar S, Mathers JC

Publication type: Review

Publication status: Published

Journal: British Journal of Nutrition

Year: 2015

Volume: 113

Issue: 8

Pages: 1182-1194

Print publication date: 01/04/2015

Online publication date: 31/03/2015

Acceptance date: 06/01/2015

ISSN (print): 0007-1145

ISSN (electronic): 1475-2662

Publisher: CAMBRIDGE UNIV PRESS

URL: .http:/dx.doi.org/10.1017/S0007114515000227

DOI: 10.1017/S0007114515000227


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