Arginine is the body's chief source for creating Nitric Oxide (Source : The Arginine Solution, 1999)

In fact, we can obtain free-form Arginine from plant and animal protein in our diet. When the food undergoes digestion, the protein will be broken down into different free-form amino acids, in which include free-form Arginine that will be used by our body to produce Nitric Oxide (NO). However, our digestive systems weaken with the aging process making it difficult to break down food proteins completely into free-form amino acids. Consequently, free-form Arginine becomes deficient in our body and hence resulting in reduced NO production.

Arginine is a scientifically proven supplement that increases the production of Nitric Oxide.