The effect of l-arginine supplementation on lipid profile: a systematic review and meta-analysis of randomised controlled trials

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 center dot 03 mg/dl; 95 % CI -10 center dot 78, 0 center dot 73; P = 0 center dot 08; inconsistency index (I-2) = 39 center dot 0 %), LDL (WMD: -0 center dot 47 mg/dl; 95 % CI -3 center dot 61, 2 center dot 66; P = 0 center dot 76; I-2 = 0 center dot 0 %), or HDL (WMD: 0 center dot 57 mg/dl; 95 % CI -1 center dot 28, 2 center dot 43; P = 0 center dot 54; I-2 = 68 center dot 4 %). A significant reduction was observed only in serum TAG levels (WMD: -7 center dot 04 mg/dl; 95 % CI -11 center dot 42, -2 center dot 67; P < 0 center dot 001; I-2 = 0 center dot 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.