l-arginine + l-citrulline

**l-arginine + l-citrulline** is a combination of two naturally occurring amino acids, often used as a dietary supplement. Both amino acids play crucial roles in the urea cycle and nitric oxide (NO) metabolism. L-arginine acts as a substrate for nitric oxide synthase to produce nitric oxide, a potent vasodilator that regulates blood flow, vascular tone, and cardiovascular health. L-citrulline is a precursor to L-arginine and can increase plasma arginine levels, enhancing nitric oxide production. The combination is believed to provide synergistic elevation of plasma arginine and NO levels, potentially improving vascular health, exercise performance, and symptoms in certain cardiovascular or metabolic diseases. Clinical studies indicate benefits in exercise endurance, blood pressure reduction, and amelioration of certain disease symptoms associated with impaired NO synthesis. Mechanistically, much of the effect centers on augmentation of NO production and subsequent vasodilation and improved endothelial function[1][2][5][6].