Nitric oxide supplements may increase athletic performance by increasing blood flow to the muscles, which also supplies additional nutrients and oxygen, according to MedFitness. This can increase strength and improve recovery times.
NO supplements take the form of L-arginine, which is a naturally occurring amino acid found in nuts and seeds, notes MedFitness. It is marketed as nitric oxide because it turns into gas nitrous oxide in the body. NO is a vasodilator, which means it widens arteries and veins. It does have this effect in people at rest, but studies on the effects of NO supplementation during exercise have been contradictory. A 2012 study published by the National Center for Biotechnology Information indicates that previous studies showed little benefit for exercise and had been performed mostly on young male subjects, so NO's effect on women is largely unknown.
NO supplementation can have negative side effects, according to MedFitness. People who have the herpes simplex virus should avoid it because it can stimulate virus growth. It may also have adverse reactions with certain drugs, including nitroglycerine and erectile dysfunction medications. People taking these or other medications should consult their doctors before beginning L-arginine supplementation. Overdosing can also have adverse effects, including weakness, diarrhea, headaches and nausea. Standardized dosing guidelines have not been established for NO, as noted by Men's Fitness.