fa public specific orginal article <p><em><strong>Background:</strong></em> Sexual dysfunction is an important health problem which prevalence in patients with type 2 diabetes (T2D) is higher than other people. The aim of this study was to evaluate the effect of L-arginine oral supplementation on sexual function in men with T2D and mild-to-moderate erectile dysfunction (ED). <em><strong>Methods: </strong></em>Eighty men with T2D, suffering from mild-to-moderate erectile dysfunction participated in this double-blind clinical trial. <em>They were randomly assigned in to two groups; receiving 5 g/day L-arginine (AG) or placebo group (PG) for 4 weeks.</em> <em>Sexual functions were recorded with i</em>nternational index of erectile function <em>questionnaire at the beginning and end<br> of the intervention.</em> <em>Total testosterone concentrations were measured too. <strong>Results:</strong></em> The total mean score of sexual function parameters significantly increased only in AG than PG (43.2 &plusmn; 6.2 vs. 39.4 &plusmn; 4.0, <em>P</em> = 0.003).<em> Against</em> PG, the mean of all parameters significantly improved in AG after intervention. <em>Only the mean score of erectile function in AG had a significant increase compared to PG. Mean of other sexual activity scores between the two groups had no significant differences.</em> The mean of testosterone concentration had a significant increase in both groups after the intervention, but the mean of changes was significantly higher in AG than in PG (1.91 &mu;g/L vs. 0.53 &mu;g/L, <em>P</em> = 0.004). <em><strong>Conclusions:</strong></em><em> The present trial showed that daily consumption of 5 g L-arginine for four weeks in T2D men with </em>mild-to-moderate <em>sexual dysfunction improved various parameters such as erectile function,</em> sexual satisfaction, sexual desire, pleasure from sexual intercourse, and testosterone level.</p> Arginine supplementation, Diabetes mellitus, Erectile dysfunction, Sexual dysfunction, Testosterone 165 172 http://jnfs.ssu.ac.ir/browse.php?a_code=A-10-1-31&slc_lang=fa&sid=1 Hassan Mozaffari-Khosravi Yes Department of Nutrition, School of Public Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Mosayeb Fallahi No Department of Nutrition, School of Public Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Mohammad Afkhami-Ardekani No Department of Internal Medicine, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran