The amino acid arginine has several roles in the body, such as assisting in wound healing, helping remove excess ammonia from the body, stimulating immune function, and promoting secretion of several hormones, including glucagon, insulin, and growth hormone.

The effect of arginine on growth hormone levels has interested body builders. In a controlled trial, when arginine and ornithine (500 mg of each, twice per day, five times per week) were combined with weight training, a greater decrease in body fat was obtained after only five weeks than when the same exercise was combined with a placebo.

Arginine is also needed to increase protein synthesis, which can in turn increase cellular replication. Therefore, arginine may help people with inadequate numbers of certain cells. For example, some, though not all, studies have found that men with low sperm counts experienced an increase in the number of sperm when they supplemented with arginine.