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Ornithine

Synonyms/Common Names/Related Substances:

  • (+)-(S)-2,5-Diaminopentanoic acid, (+)-(S)-2,5-diaminovaleric acid, amino acid, guanidinium, L-arginine, L-norvaline, L-ornithine, L-ornithine-L-aspartate, ornithine (VAN), ornithine hydrochloride, ornithinum (Latin), putrescine, (S)-ornithine, urea.

Clinical Bottom Line/Effectiveness

Brief Background:

  • Ornithine is a nonessential amino acid in the human body and is not coded for by DNA. It is not used in protein synthesis. In the body, it is produced in the urea cycle (disposal of excess nitrogen) during the breakdown of L-arginine by the enzyme arginase. During the cycle, ornithine is recycled and acts as a catalyst. In the urea cycle, ammonia is converted into carbamoyl phosphate, an intermediate of urea. Ornithine reacts with carbamoyl phosphate, replacing the phosphate group to form citrulline. Following two additional enzymatic reactions, fumarate is released and arginine is formed. The arginine is hydrolyzed back to ornithine (by arginase), resulting in the production of urea.
  • In the popular literature, ornithine is of interest to bodybuilders because of its potential to stimulate growth hormone and therefore to have possible anabolic effects. It is traditionally used for exercise performance improvement. Medical uses include combining ornithine with a nonessential amino acid aspartate, creating a stable salt for ammonia toxicity and encephalopathy associated with serious liver ailments.
  • Although there is evidence in support of the clinical use of ornithine aspartate for ammonia toxicity and hepatic encephalopathy, the evidence in support of ornithine alone is lacking at this time. Ornithine hydrochloride has mixed benefits with respect to exercise performance. Further clinical research is needed in all areas at this time.

Dosing/Toxicology

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Precautions/Contraindications

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Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.

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Mechanism of Action

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History

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Evidence Table

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Evidence Discussion

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Products Studied

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Author Information

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References

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

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The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.