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Clinical evidence has suggested that alpha-lipoic acid (ALA), a potent antioxidant, seems to have some effects on inflammatory process. However, these results are equivocal. The purpose of this paper is to investigate the nature of association between ALA and serum C-reactive protein (CRP) level by pooling the results from clinical trial studies.

Relevant studies were identified by systematic literature search of PubMed/MEDLINE, Scopus, Web of Sciences and Cochrane library up to September 2016 for randomized controlled trials (RCTs) evaluating the impact of ALA supplementation on CRP. The pooled data were summarized as weighted mean difference (WMD) and 95 per cent confidence interval (CI). Effect sizes of eligible studies were pooled using random- or fixed-effects (the DerSimonian–Laird estimator) depending on the results of heterogeneity tests.

Of 212 papers, 15 were eligible RCTs according to inclusion criteria. The selected studies comprised 1,408 cases and 457 controls. The dose of ALA supplement ranged from 300 to 1,200 mg, and the duration of follow-up was from 1 to 48 weeks. ALA supplementation significantly reduced the levels of circulating CRP (WMD: −0.088, 95 per cent CI: −0.131, −0.045, p < 0.001) with significant heterogeneity (I² = 73.4 per cent, p < 0.001). Populations with age younger than 50 years (PMD: −0.060 mg/dl), receiving doses less than 600 mg/day (PMD: −0.057 mg/dl), having cardiovascular disease (PMD: −0.105 mg/dl), hemodialysis (PMD: −0.209 mg/dl), diabetes (PMD: −0.021 mg/dl) and otherwise healthy subjects (PMD: −0.045 mg/dl) were sources of heterogeneity.

This meta-analysis of RCTs suggests that ALA supplementation seems to significantly reduce circulating CRP level.