Citrulline
L-Citrulline is a non-essential amino acid that is converted to arginine in the kidneys, more efficiently raising plasma arginine than direct arginine supplementation. Evidence for blood pressure reduction, exercise performance, and erectile function.
How it works (mechanism of action)
Converted to arginine by ASS1 and ASL enzymes in kidneys and intestinal cells — bypasses first-pass hepatic metabolism of arginine. Arginine is then converted to nitric oxide by NOS. Citrulline malate combines with malic acid for additional ergogenic effect.
Evidence grades: A=Strong RCT evidence · B=Good clinical trials · C=Limited trials · D=Preliminary/traditional
Very safe. No significant drug interactions identified. Mild gastrointestinal effects possible at high doses. Safe alternative to arginine for NO-mediated vasodilation.