A number of clinical trials have examined the effect of l-arginine on lipid profile in recent years; however, the results remain equivocal. Therefore, the present study aims to summarise and quantitatively examine the available evidence on the effectiveness l-arginine supplementation on lipid parameters using a systematic review and meta-analytic approach. Online databases including PubMed, Scopus, ISI Web of Science, Cochrane Library and Google Scholar were searched up to April 2019 for randomised controlled trials that examined the effect of l-arginine supplementation on lipid profile in adults. Treatment effects were expressed as weighted mean difference (WMD) and the corresponding standard error in concentrations of serum lipids. To estimate the overall effect of l-arginine supplementation, we used the random-effects model. In total, twelve studies were included in the systematic review. The meta-analysis revealed that l-arginine supplementation did not significantly change the concentrations of total cholesterol (WMD: -5·03 mg/dl; 95 % CI -10·78, 0·73; P = 0·08; inconsistency index (I2) = 39·0 %), LDL (WMD: -0·47 mg/dl; 95 % CI -3·61, 2·66; P = 0·76; I2 = 0·0 %), or HDL (WMD: 0·57 mg/dl; 95 % CI -1·28, 2·43; P = 0·54; I2 = 68·4 %). A significant reduction was observed only in serum TAG levels (WMD: -7·04 mg/dl; 95 % CI -11·42, -2·67; P < 0·001; I2 = 0·0 %). This meta-analysis concludes that l-arginine supplementation can significantly reduce blood TAG levels; however, there is insufficient evidence to support its hypocholesterolaemic effects. To draw straightforward conclusions regarding generalised recommendations for l-arginine supplementation for improving lipid profile, there is a need for more well-controlled trials targeting exclusively patients with dyslipidaemia.
Keywords: Lipid profile; Meta-analyses; Supplementation; Systematic reviews; l-Arginine.