L-Arginine promotes optimal endothelial function, meta-analysis shows

Summary

This meta-analysis was designed to investigate the effect of oral l-arginine supplementation on endothelial function, as measured by fasting flow-mediated dilation (FMD).

Eligible for inclusion were randomized, placebo-controlled l-arginine supplementation trials evaluating endothelial function. Trials were identified in PubMed, Cochrane Library, Embase, reviews, and reference lists of relevant papers. The weighted mean difference (WMD) was calculated for net changes in FMD by using random-effect models. Subgroup analyses and meta-regression analyses were performed to explore the influence of study characteristics.

Thirteen trials met the inclusion criteria and were included in the analysis. Studies had significant heterogeneity largely explained by the baseline FMD. The average age of the patients varied from 12 to 74 years, dosages of l-arginine ranged from 3 to 24 g/day, typically in split doses 2-3 times daily, and treatment duration varied from 3 days to 6 months. Because there was only one long-term study (3 g/day for 180 days), the researchers focused on short-term effects of l-arginine (12 studies, 492 participants).

In an overall pooled estimate, l-arginine significantly increased FMD (WMD: 1.98%; 95% CI: 0.47, 3.48; P=.01). Meta-regression analysis indicated that the baseline FMD was inversely related to effect size. A subgroup analysis suggested that l-arginine supplementation significantly increased FMD when the baseline FMD levels were less than 7% (WMD: 2.56%; 95% CI: 0.87, 4.25; P=.003), but had no effect on FMD when baseline FMD levels were greater than 7% (WMD: -0.27%; 95% CI: -1.52, 0.97; P=.67).

These findings suggest that short-term use of oral l-arginine is effective at improving fasting vascular endothelial function when baseline FMD is low.