Arginine is converted to nitric oxide by nitric oxide synthase (NOS). NO relaxes blood vessel smooth muscle, lowering blood pressure and improving blood flow, including to the penis (ED mechanism) and muscles (exercise). The problem: oral arginine is heavily metabolized by the enzyme arginase in the gut wall and liver before it reaches the bloodstream. This is why citrulline, which bypasses arginase and converts to arginine in the kidneys, actually raises blood arginine levels MORE than arginine itself.
Independently graded against 173,636 indexed supplements with 177 published clinical interactions, sourced from PubMed, FDA CAERS, openFDA, and NIH DSLD | Last updated:
Not medical advice. Based on published clinical research and systematic reviews.