L-Citrulline is an amino acid that supports the body in optimizing blood flow through its conversion to L-arginine and then nitric oxide. Nitric oxide is involved in vasodilatation and low levels are associated with mental and physical fatigue and sexual dysfunction.

L-Citrulline is a nonessential amino acid, which is not found in dietary protein. L-Citrulline is a precursor to the formation of L-Arginine and thus plays a vital role in Arginine recycling, which is an important factor in nitric oxide release.

Citrulline supplementation provides a readily available source of citrulline for this purpose, and some recent research further indicates that citrulline may even be the preferred source of cellular Arginine. Citulline is one of the key elements to Nitric Oxide production that is overlooked. Citrulline is involved in the catabolism of the amino acid, L-arginine. In bacteria, the arginine dihydrolase pathway deaminates arginine to citrulline and splits citrulline into ornithine and carbamoyl phosphate. This pathway is a source of energy for many microorganisms and is used as an identifying test.