Background: L-arginine, being the substrate for endothelial nitric oxide synthase, is essential for normal endothelial function. Endothelial dysfunction is accompanied by increased arterial stiffness. Aim of the study was to investigate in healthy smokers the effect of a short-term daily L-arginine administration on vascular function.

Methods: We studied the effect of a 3-day oral administration of L-arginine in 12 healthy smokers (aged 24±3 yrs) on 3 occasions (day 0: baseline measurements, day 1 and day 3). The study was carried out on two separate arms, one with L-arginine (7 g tid) and one with placebo according to a randomized, placebo-controlled, double-blind, cross-over design. All measurements were performed one hour after L-arginine or placebo intake. Endothelial function was evaluated with flow-mediated dilatation (FMD) of the brachial artery. Carotid-femoral pulse wave velocity (PWV) was measured as an index of aortic stiffness and augmentation index (AIx) as a measure of wave reflections

Results: Compared to placebo, L-arginine led to a progressive increase of FMD (by 1.74%, p = NS at day 1 and by 1.96%, p < 0.05 at day 3), indicating a favorable effect on endothelial function. Moreover, L-arginine intake led to a progressive decrease of PWV (by 0.32m/s at day 1 and by 0.36 m/s at day 3, both p < 0.01) and of AIx (by 5.1%, p < 0.01 at day 1 and by 9.3%, p < 0.001 at day 3), indicating a decrease in aortic stiffness and wave reflections.

Conclusion: Short-term daily administration of L-arginine, improves arterial performance in healthy smokers. These findings provide further insights into the cardiovascular profile of this molecule.