In amateur male triathletes aged 48.1 ± 9.8 years, seven days of daily beetroot-based nitrate supplementation (0.77 g nitrate plus L-citrulline, L-arginine, and N-acetylcysteine) increases plasma and urinary nitric oxide metabolites by approximately 155%, elevates inducible nitric oxide synthase by 56%, and raises peroxynitrite levels by 60%, without evidence of lipid peroxidation.

Dietary nitrate from beetroot is converted into nitrite by bacteria in the mouth, then into nitric oxide in the body, especially where oxygen is low. This nitric oxide combines with another molecule called superoxide to form peroxynitrite, a signaling compound. At the same time, the body makes more of an enzyme that produces even more nitric oxide. These changes boost signaling without damaging cell membranes because antioxidants in the supplement and the body's own defenses keep the system balanced.