Arginine is an α-amino acid which is conditionally essential depending on the developmental stage and health status of each person. For instance, preterm infants are not able to metabolize arginine internally, making the amino acid nutritionally indispensable for them. In contrast, most healthy adults do not need it since the body typically produces plentiful amounts that help the organism produce protein. The possible benefits of L-arginine include nitric oxide production enhancement, growth hormone stimulation, reduction of anxiety, and increase in libido and physical activity.
In the brain, L-arginine acts as a neurotransmitter; in the immune system, it acts as a mediator of host defense; and in the cardiovascular system, it mediates the protective effects of the intact endothelium, acting as a vasodilator and endogenous, antiatherogenic molecule. About 5 g of L-arginine are ingested each day in a normal Western diet, nutritional plan that has been shown to improve the symptoms of cardiovascular disease .Thus, L-arginine supplementation has also been shown to aid in lowering blood pressure in individuals with hypertension.
Furthermore, a 1-year follow-up study of a mentally retarded child , aged 9.6 years, with CT1 defect, showed that oral supplementation with L-arginine, produced a noticeable improvement of neurological, language and behavioral status and an increase of brain creatine. This makes L-arginine a particularly appealing precursor of creatine synthesis that has been shown to be beneficial even in healthy subjects, especially for the ones who are physically active .
To sum up, arginine works by ridding the body of waste and also in the synthesizing of proteins. This is the mechanism that underlies its regenerative capabilities when involved in various body systems. In conclusion, the effects of L-arginine supplementation on human physiology appear to be multicausal and dose-related. Doses of 3-8 g/d appear to be safe and not to cause acute pharmacologic effects in humans .