Ornithine is a non-protein amino acid belonging to the group of endogenous amino acids. In the body, it is formed from another amino acid – arginine, under the influence of an enzyme called arginase. A good external source of ornithine is animal protein, eggs, and dairy products. It can also be supplied with supplements. They usually include a free hydrochloride-stabilized form of ornithine.

In the body, ornithine plays an important role in the so-called urea cycle of Krebs. The process neutralizes ammonia, which is a toxic, by-product of metabolic transformations taking place in the body. Ornithine performs the function of a catalyst in this process – it enables the conversion of ammonia into harmless urea, which is eliminated from the body along with the urine. In addition, it is a precursor to important compounds such as glutamic acid, proline, and citrulline.

In supplementation, ornithine is mainly used for sports and health-promoting purposes. Long, intense training sessions often correlate with the increased production of ammonia, which in turn reduces the efficiency of the body. Increasing the supply of ornithine promotes the reduction of fatigue after such effort. In addition, ornithine is credited with the ability to raise the level of growth hormone and to reduce cortisol levels. This results in a better well-being and facilitates the work on the body.