L-ornithine

What is ornithine?

Ornithine is an amino acid that is not used to build proteins. It plays an important role in the urea cycle together with the amino acids citrulline and arginine.

Where does ornithine come from?

Ornithine is produced in the body from the essential amino acid L-arginine. This takes place as part of the previously mentioned urea cycle. The urea cycle is a series of chemical reactions that take place in the body to detoxify nitrogenous waste products.

Health benefits of ornithine

Because of its role in the breakdown of ammonia, ornithine is used to treat conditions that involve an accumulation of ammonia in the body fluids. Hepatic encephalopathy is a disease of the liver that causes high blood levels of ammonia, which can impair cognitive function. Ornithine has been shown to significantly reduce ammonia levels, especially at high doses.

Benefits of ornithine for bodybuilders

An accumulation of ammonia in the muscles is a factor that can contribute to muscle fatigue. Supplementation with ornithine can reduce this effect. It appears to reduce the subjective feeling of fatigue and enable longer training sessions. In addition, several studies have shown an increase in strength and power release after several weeks of ornithine supplementation. One study showed an increase in muscle mass over a period of 5 weeks. However, as ornithine was administered in conjunction with arginine in this study, this result cannot be clearly attributed to ornithine. Ornithine can also increase growth hormone levels in the body by a significant percentage at higher doses. However, these effects are only temporary and it is therefore likely that continuous supplementation is required to benefit from them. Ornithine is often used as a nitric oxide booster due to its link to the urea cycle and the nitric oxide cycle. This effect can increase blood flow, muscle pump and the effectiveness of a training session.

Side effects and safety

Large doses of ornithine can cause diarrhea. The active dose appears to be much lower than the dose at which side effects occur, so there is a significant safety buffer. In order to achieve an effect on human growth hormone levels, the ornithine dosages required for this are in the range above which symptoms may occur in the digestive tract.

Recommended intake

Ornithine is generally used in dosages of 2 to 6 grams per day. The benefits of ornithine appear to be dose-dependent, meaning that higher doses have a stronger effect. You can take up to 10 grams of ornithine before digestive tract symptoms occur in people who are sensitive to it.

Ornithine supplement

Ornithine is available as an isolated amino acid and can also be found in many pre-workout supplements, intra-workout supplements and nitric oxide boosters.

Possible combinations of ornithine with other supplements

Due to its ability to reduce fatigue and increase nitric oxide levels, ornithine can be combined well with pre-workout supplements.

References

1. Demura S, et al. The effect of L-ornithine hydrochloride ingestion on performance during incremental exhaustive ergometer bicycle exercise and ammonia metabolism during and after exercise. Eur J Clin Nutr (2010)
2. Grimble GK. Adverse gastrointestinal effects of arginine and related amino acids. J Nutr (2007)
3. Mutch BJ, Banister EW. Ammonia metabolism in exercise and fatigue: a review. Med Sci Sports Exerc. (1983)
4. Zajac A, et al. Arginine and ornithine supplementation increases growth hormone and insulin-like growth factor-1 serum levels after heavy-resistance exercise in strength-trained athletes. J Strength Cond Res (2010)
5. Sugino T, et al. L-ornithine supplementation attenuates physical fatigue in healthy volunteers by modulating lipid and amino acid metabolism. Nutr Res (2008)