The effect of alpha-lipoic acid on inflammatory mediators: a systematic review and meta-analysis on randomized clinical trials

Abstract

Alpha-Lipoic Acid (ALA) is a natural antioxidant compound which is naturally found in plant sources. New evidence revealed that ALA can reduce inflammation. Our objective in this meta-analysis was to conduct a systematic review and meta-analysis on randomized controlled trials to indicate ALA effects on serum inflammatory mediators concentration such as tumor necrosis factor-alpha (TNF-α), c-reactive protein (CRP), and interleukin-6 (IL-6). In order to find relevant articles we performed a systematic research up to June 2018 using EMBASE, ISI web of science, Scopus, PubMed, and Google scholar. The overall treatment effect for each inflammatory marker was calculated as weighted mean differences (WMD) and corresponding 95% of confidence interval (CI) between changes in intervention and control groups. Changes for each parameter were calculated by subtracting baseline values from the final mean values. The I2 statistic was used to examine between-study heterogeneity. When heterogeneity was > 25%, random effect model was run to estimate pooled effect size. There had been nineteen articles in our meta-analysis and twenty-one articles in systematic review. Our meta-analysis results indicated that ALA significantly decreased serum CRP levels (WMD= −0.29, 95% CI: −0.46, −0.12; I2 =97.6%, P < 0.0001), IL-6 (WMD= −3.02, 95% CI: −4.03, −2.01; I2 =99.7%, P < 0.0001) and TNF-α levels (WMD= −1.71, 95% CI: −2.30, −1.13; I2 =99.0%, P < 0.0001). Our results indicated possible decreasing effect of ALA on inflammatory mediators especially in high dose. More randomized clinical trials (RCTs) are necessary with different intervention duration and on women and men separately.