:Ornithine:

Function: growth promotion.

L-Ornithine is a precursor of citrulline and arginine and when given orally, has very similar biological effects. It is a naturally occurring amino acid and is different from arginine in that it is not found incorporated into body proteins. Almost all recommendations given for therapeutic uses of arginine probably apply also to Ornithine.

Orally supplemented Ornithine can be converted by the body into arginine, glutamine or proline. Arginine is its primary end product and supplemental arginine is immediately converted back to Ornithine. Ornithine can also be converted into polyamines. Lysine, an antagonist of arginine, also prevents uptake of Ornithine.

Ornithine may enter the mitochondria more readily than arginine, so it is possible that L-Ornithine may be a better arginine supplement than arginine itself. L-Ornithine as 3000 mg tablets A.M. and P.M. is part of a recently formulated growth hormone-releasing supplement. We think that this dose may be too low to have a significant result.

L-Ornithine, 500 mg, is readily available. No toxicity has been reported. We have found doses as low as 1 g to cause insomnia in some individuals. Yet, in general, Ornithine supplementation is well tolerated, up to several grams daily and probably higher doses. The effect of mega Ornithine therapy, 10 g daily, for prolonged periods has not been investigated.

Arginine is an Ornithine agonist, while lysine inhibits Ornithine metabolism.
Ornithine supplements, like arginine may be useful in a variety of diseases. Ornithine releases growth hormone and may be of value for growth-impaired children and athletes in training.