Nitric Oxide is a molecule consisting of one atom of nitrogen and one atom of oxygen. The production of Nitric Oxide occurs when the amino acid L-arginine is converted into L-citruline through an enzyme group known as Nitric Oxide Synthase (NOS). The chemical process of conversion is shown in figure 1.

"Summary research papers continue to flood the scientific journals and insights into the biological activity and potential clinical uses of nitric oxide (NO): a gas controlling a seemingly limitless range of functions in the body. Each revelation adds to nitric oxide's already lengthy resume in controlling the circulation of the blood, regulating activities of the brain, lungs, liver, kidneys, stomach and other organs.

The molecule governs blood pressure through a recently recognized process that contradicts textbook wisdom. It causes penile erection by dilating blood vessels and controls the action of almost every orifice from swallowing to defecation. The immune system uses nitric oxide in fighting viral, bacterial and parasitic infections, and tumors. Nitric oxide transmits messages between nerve cells and is associated with the process of learning, memory, sleeping, feeling pain, and, probably depression. It is a mediator in inflammation and rheumatism."

Since the above was written in 1996, Nitric Oxide containing products have continued to be touted by those in the medical profession, as well as by athletes looking to add muscle to their frames.

The above quotation states that Nitric Oxide controls the circulation of blood, transmits messages between nerve cells, and is a mediator of inflammation and is associated with the process of feeling pain. The popular erectile dysfunction drug sildenafil citrate (Viagra) contains nitric oxide and is responsible for increasing blood flow to the penis.

The fact that nitric oxide increases blood flow should make it of interest to bodybuilders, as increased blood flow will serve to deliver more nutrients to muscles, thus helping muscles become larger when subject to stress. The fact that Nitric Oxide acts to reduce inflammation should also make it of interest to bodybuilders as it has the potential to reduce the pain associated with subjecting muscles to extreme stress.

Nitric oxide also affects the endocrine system. It affects the release of gonadotroptin releasing hormone, as well as the release of adrenaline from the adrenal medulla.

Signs of deficiency include the inability to achieve and sustain erections, physical weakness and extreme fatigue. Most "nitric oxide" supplements contain the amino acid Arginine-alpha-keto-glutarate.