Nitric oxide precursors are substances that the body converts into nitric oxide, a molecule important for various physiological functions. Common precursors include L-arginine and L-citrulline, which are amino acids found in foods like meat, fish, and nuts. These compounds help improve blood flow, support cardiovascular health, and enhance exercise performance by promoting vasodilation, or the widening of blood vessels. When consumed, L-arginine is directly converted into nitric oxide, while L-citrulline is first transformed into L-arginine before producing nitric oxide. This conversion process makes L-citrulline often more effective in raising nitric oxide levels, especially during physical activity.