Effect of vitamin C and vitamin E supplementation on endothelial function: a systematic review and meta-analysis of randomised controlled trials
What this study found
Vitamin C alone and vitamin E alone improved endothelial function, but combined vitamin C plus vitamin E supplementation did not. Pooled analyses included 17 vitamin C-alone trials with 478 participants, 27 vitamin E-alone trials with 742 participants, and 14 combined-vitamin trials with 597 participants. Benefits appeared greater in older individuals for vitamin C and in those with lower baseline vitamin E status for vitamin E, supporting a potentially personalized approach. The overall conclusion was that single-agent antioxidant supplementation may help endothelial function, whereas…
- Study & population
- Systematic review and meta-analysis of randomized controlled trials in adults with varied health status, including healthy participants and individuals with cardiovascular risk factors or disease.
- Intervention
- Oral vitamin C and/or vitamin E supplementation was evaluated across randomized trials, with doses ranging from 300 mg to 2000 mg for vitamin C and from 400 IU to 1800 IU for vitamin E.
- Key limitation
- The evidence base was heterogeneous in participant health status, baseline vitamin status, supplement dose, duration, and endothelial function measurement methods.
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Open PDFOriginal 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 (β 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 (β − 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.