Vitamin C in post-exercise recovery: what does the best available evidence actually tell us?
Niassa Linea de Souza Silva e Silva, Weverton Pereira de Medeiros, Geanderson Sampaio de Oliveira, Aline Bergamini Effgen Sena, Luana da Silva Baptista Arpini
ABSTRACT
This paper offers a critical appraisal of the article Effect of Vitamin C Supplementation on Post-Exercise Recovery: A Systematic Review and Meta-Analysis of Randomized Double-Blind Placebo Trials, published as a preprint in Clinical Nutrition ESPEN by Bruno M. Candeloro and colleagues¹. The study aimed to quantify the effects of oral vitamin C supplementation on post-exercise inflammatory and oxidative stress biomarkers through a systematic review and meta-analysis. Conducted in accordance with PRISMA guidelines and prospectively registered in PROSPERO (CRD42024594742), the review was restricted to randomized double-blind placebo-controlled trials, a criterion that strengthens internal validity at the cost of a smaller evidence base. Twelve trials were included, with vitamin C doses ranging from 500 to 4000 mg/day across heterogeneous populations and exercise protocols. C-reactive protein (CRP), interleukin-6 (IL-6), and malondialdehyde (MDA) were the primary outcomes, assessed using RoB 2.0 for risk of bias and GRADE for certainty of evidence. A random-effects model with weighted mean differences and 95% confidence intervals was applied. Among the three outcomes, only CRP yielded a statistically significant reduction (MD = −0.44; 95%CI −0.66 to −0.22), while IL-6 and MDA showed no significant effect. Evidence certainty was rated low for CRP and IL-6 and very low for MDA, with substantial heterogeneity observed for MDA (I² = 80%). Each pooled estimate drew on no more than two to three small trials, which substantially limits the precision and generalisability of the findings. The available evidence does not support routine vitamin C supplementation as a post-exercise recovery strategy. Further high-quality trials incorporating functional endpoints and standardised supplementation protocols are needed before clinical or sports-related recommendations can be made.
Keywords: Vitamin C. Antioxidants. Inflammation. Oxidative stress. Post-exercise recovery. Meta-analysis.
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