Effects of Polyphenols Supplementation on Inflammation and Oxidative Stress after Acute Exercise: A Systematic Review with Meta-Analysis
Polyphenols are the secondary metabolites in plants and are considered reducing agents with capabilities of protecting humans from inflammation and oxidative stress. Acute exercise works as a stressor during and after performance, with the capability of causing inflammation and oxidative stress. The purpose of this research is to determine the effect of polyphenol supplementation on inflammatory markers (C-Reactive Protein, CRP; High-Sensitivity C-Reactive Protein, HS-CRP; Interleukin-6, IL-6; Interleukin-8, IL-8; and Tumor Necrosis Factor Alpha, TNF-α) and oxidative stress marker (Malondialdehyde, MDA) after acute exercise. It is hypothesized that acute exercise induced inflammation and oxidative stress will be decreased by polyphenols supplementation. A systematic review with meta-analysis was used to extract pertinent data identifying the changes of inflammatory and oxidative stress markers post-acute exercise, and polyphenol supplementation. PubMed was searched using key words "polyphenol inflammation exercise" and "polyphenol oxidative stress exercise", which produced 243 records for screening ("polyphenol inflammation exercise", results produced: n = 98, and "polyphenol oxidative stress exercise", results produced: n = 145). After screening all records and removing all duplicates, each article was assessed for eligibility based on exclusion and inclusion criteria. The total number of articles identified to be included in the study for quantitative synthesis totaled 14 ("polyphenol inflammation exercise", n = 10, and "polyphenol oxidative stress exercise", n = 4). These interventional studies focused on quantitative data pertaining to the effects of supplementation of polyphenols on inflammatory and oxidative stress markers after acute exercise, including single-, double-, and triple-blinded designs; and randomized, placebo-controlled, and crossover designs. Data were collected using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. All data collected was extracted and entered in R for statistical data analysis to create a forest plot depicting a graphical display of the results collected. A standard mean difference (SMD) comparing supplementation to placebo groups was established for all markers data extracted from this study. The results regarding the effects of polyphenol supplementation on post-acute exercise induced inflammation and oxidative stress markers varied across all studies evaluated. Based on the statistical analysis for the SMD between supplementation and control groups of each study, we found: (1) CRP, IL-8 and TNF-α levels were not affected by polyphenols supplementation after acute exercise; (2) IL-6 and MDA levels were significantly lowered with polyphenols supplementation after acute exercise. Thus, we concluded polyphenols supplementation could reduce inflammatory marker IL-6 and oxidative stress marker MDA induced by acute exercise.