In the body NO is naturally produced from L-Arginine, L-Citrulline, NADH, and Oxygen. NitroPro delivers L-Arginine via a compound called L-Arginine Alpha Keto-Gluatarate (AAKG). Our AAKG is double the potency of many other NO products on the market because we have a 2:1 ratio of Arginine to Alpha Keto Gluatarate where others use cheaper 1:1 material. Citrulline is vital to the formula because it is the other amino acid responsible for the production of NO.