The efect of vitamin E supplementation on selected infammatory biomarkers in adults: a systematic review and meta‑analysis of randomized clinical trials

Asbaghi, Omid and Nazarian, Behzad and Sarreshtedari, Mehrnoosh and Mozafari‑Khosravi, Hassan and Sadeghi, Omid (2021) The efect of vitamin E supplementation on selected infammatory biomarkers in adults: a systematic review and meta‑analysis of randomized clinical trials. Scientifc Reports.

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Abstract

The previous meta-analysis of clinical trials revealed a benefcial efect of vitamin E supplementation on serum C-reactive protein (CRP) concentrations; however, it is unknown whether this vitamin has the same infuence on other infammatory biomarkers. Also, several clinical trials have been published since the release of earlier meta-analysis. Therefore, we aimed to conduct a comprehensive meta-analysis to summarize current evidence on the efects of vitamin E supplementation on infammatory biomarkers in adults. We searched the online databases using relevant keywords up to November 2019. Randomized clinical trials (RCTs) investigating the efect of vitamin E, compared with the placebo, on serum concentrations of infammatory cytokines were included. Overall, we included 33 trials with a total sample size of 2102 individuals, aged from 20 to 70 years. Based on 36 efect sizes from 26 RCTs on serum concentrations of CRP, we found a signifcant reduction following supplementation with vitamin E (− 0.52, 95% CI − 0.80, − 0.23 mg/L, P< 0.001). Although the overall efect of vitamin E supplementation on serum concentrations of interleukin-6 (IL-6) was not signifcant, a signifcant reduction in this cytokine was seen in studies that used α-tocopherol and those trials that included patients with disorders related to insulin resistance. Moreover, we found a signifcant reducing efect of vitamin E supplementation on tumor necrosis factor-α (TNF-α) concentrations at high dosages of vitamin E; such that based on dose–response analysis, serum TNF-α concentrations were reduced signifcantly at the dosages of ≥700 mg/day vitamin E (Pnon-linearity= 0.001). Considering diferent chemical forms of vitamin E, α-tocopherol, unlike other forms, had a reducing efect on serum levels of CRP and IL-6. In conclusion, our fndings revealed a benefcial efect of vitamin E supplementation, particularly in the form of α-tocopherol, on subclinical infammation in adults. Future high-quality RCTs should be conducted to translate this antiinfammatory efect of vitamin E to the clinical setting.

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