Nitric oxide (NO) is a gas-phase signaling molecule produced by endothelial cells, neurons, and immune cells. Acts as a potent vasodilator.
Mechanism: eNOS (endothelial NO synthase) produces NO from L-arginine. NO relaxes vascular smooth muscle, increasing vessel diameter and blood flow. Production declines with age, oxidative stress, and endothelial dysfunction.
Use case: Support via L-Citrulline (better than direct L-Arginine), dietary nitrates (beets, leafy greens), exercise (chronic upregulation), and avoiding mouthwash (kills nitrate-reducing oral bacteria).
Caveats: Acute NO boosts (pre-workout) are different from chronic endothelial health. Both matter.