This study was conducted to investigate whether regular dietary intake of l
-arginine is associated with serum nitrate + nitrite (NOx). In this cross-sectional study, 2771 men and women, who had participated in the third examination of the Tehran Lipid and Glucose Study (2006–2008), were recruited. Demographics, anthropometrics and biochemical variables were evaluated. Dietary data were collected using a validated 168-food item semi-quantitative food frequency questionnaire and dietary intake of l
-arginine was calculated. To determine any association between dietary l
-arginine and serum NOx, linear regression models with adjustment for potential confounders were used. Mean age of participants (39.2% men) was 45.9 ± 15.9 years. After adjustment for all potential confounding variables, a significant positive association was observed between l
-arginine intake and serum NOx concentrations in the fourth quartile of l
-arginine (β = 6.63, 95% CI = 4.14, 9.12, p
for trend = 0.001), an association stronger in women. Further analysis, stratified by age, body mass index and hypertension status categories, showed a greater association in middle-aged and older adults (β = 9.12, 95% CI = 3.99, 13.6 and β = 12.1, 95% CI = 6.48, 17.7, respectively). l
-arginine intakes were also strongly associated with serum NOx levels in overweight and obese subjects in the upper quartile (β = 10.7, 95% CI = 5.43, 16.0 and β = 11.0, 95% CI = 4.29, 17.5); a greater association was also observed between l
-arginine intakes and serum NOx in non-hypertensive (HTN) compared to HTN subjects (β = 2.65, 95% CI = 2.1–3.2 vs.
β = 1.25, 95% CI = −1.64–4.15). Dietary l
-arginine intakes were associated to serum NOx and this association may be affected by sex, age, body mass index, and hypertension status.