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Ornithine: Review, Benefits, Dosage & Side Effects

Quick Summary

  • Ornithine is a non-essential, non-protein amino acid crucial in the urea cycle
  • Unlike protein-building amino acids, Ornithine focuses on metabolic pathways
  • Produced primarily in the liver, Ornithine can also be sourced from meat, fish, & dairy
  • Ornithine aids in the conversion of ammonia to urea, which is essential for detoxification
  • Elevated ammonia levels can harm the nervous system & liver, making Ornithine crucial
  • Ornithine improves athletic performance & recovery by reducing fatigue & boosting growth hormone
  • It acts as a nitric oxide booster, enhancing blood flow & muscle pump during workouts
  • Ornithine lowers cortisol levels, reducing stress & improving sleep quality
  • It plays a role in immune function through nitric oxide production
  • Early research suggests Ornithine may have antioxidant & anti-aging properties
  • It may improve liver function & aid in wound healing, although more research is needed
  • Works well in synergy with amino acids like arginine, citrulline & lysine
  • Standard dosage is 2-6 grams per day
  • The potential side effects may include gastrointestinal issues


Ornithine (also known as l-ornithine) is a non-essential, non-protein amino acid that plays a critical role in the urea cycle. Though it's less commonly discussed than its more famous counterparts like arginine or citrulline, Ornithine holds a multitude of health benefits that can improve your athletic performance, stress response, & even your sleep.

This article dives deep into what Ornithine is, how it works, and why you might consider adding it to your supplement stack.

What is Ornithine?

Ornithine is an amino acid that doesn't participate in synthesizing proteins but plays a significant role in the urea cycle. Unlike the 20 standard amino acids used to build proteins, Ornithine works behind the scenes in metabolic pathways that help to detoxify ammonia & regenerate other amino acids.

Where Does Ornithine Come From?

Your body naturally produces Ornithine, primarily in the liver. It can also be obtained through diet, particularly in meat, fish, and dairy products. In addition to natural sources, Ornithine is also available in supplement form, either as a standalone product or combined with other amino acids.

The Urea Cycle & Ornithine

The urea cycle is the body's natural way of detoxifying ammonia, which is a by-product of protein metabolism. Ornithine is a key player in this process, facilitating the conversion of ammonia to urea, which is then excreted through urine.

Without sufficient Ornithine, ammonia levels could rise dangerously, affecting various bodily systems including the nervous system & the liver.

Major Benefits of Ornithine

Enhancing Athletic Performance & Recovery

Ornithine has been found to reduce fatigue and improve measures of athletic performance. When combined with arginine, it can increase growth hormone levels, facilitating quicker recovery after strenuous activities.

Ornithine is often used as a nitric oxide booster due to its link to the urea and nitric oxide cycles. This can increase blood flow, muscle pump, & effectiveness during a workout.

Stress & Sleep Benefits

Studies have shown that Ornithine can effectively reduce cortisol levels, the hormone responsible for stress. By lowering cortisol, it also improves sleep quality. In Japan, it is marketed as a supplement to improve sleep & reduce fatigue.

Immune System Boost

Ornithine's role in the urea cycle also means it plays a part in immune function. It aids in the production of nitric oxide, a molecule that helps defend against pathogens.

Potential Anti-Aging Properties

Although more research is needed, initial studies have shown that Ornithine has antioxidant properties that may help to counteract the aging process at a cellular level.

Additional Health Benefits

There's also some evidence to suggest that Ornithine can help improve liver function, particularly in detoxification processes, & may even aid in wound healing. Each of these claims is supported by a variety of scientific studies, making Ornithine a well-researched supplement with a range of benefits.

Ornithine & Other Amino Acids

Ornithine works well when combined with other amino acids like arginine, citrulline & lysine. These amino acids often act synergistically, particularly in processes like nitric oxide production, & the production of natural growth hormone.

How to Take Ornithine

A standard dosage recommendation for Ornithine varies, but 2-6 grams per day is common. However, always consult with a healthcare provider for personalised advice, especially if you belong to certain groups, such as pregnant women or those with liver conditions.

Side Effects & Safety Concerns

Ornithine is generally well-tolerated, but high doses may result in gastrointestinal discomfort or diarrhea. If you're taking medications or have existing health conditions, consult a healthcare provider before adding Ornithine to your regimen.

Ornithine in the Marketplace

Ornithine supplements are readily available online & in reputable supplement stores. In Australia, Elemental Nutrition is known for providing high-quality Ornithine powder.

Ornithine: Frequently Asked Questions

  • What does ornithine do for bodybuilding? Ornithine helps reduce muscle fatigue and improve recovery, aiding in more intense workouts.
  • Does L-Ornithine help build muscle? Yes, L-Ornithine can enhance recovery, potentially leading to better muscle gains.
  • Is L-ornithine good for weight loss? Yes, limited studies suggest L-Ornithine may support fat metabolism, aiding in weight loss.
  • Does ornithine increase growth hormone? Some research indicates that ornithine can stimulate the release of growth hormone, but findings are mixed.
  • Should you take Ornithine before or after a workout? Taking Ornithine before a workout may enhance performance & reduce fatigue.
  • Why take arginine and ornithine together? Combining these amino acids can optimise the urea cycle, potentially improving performance & recovery.
  • Who should not take ornithine? Individuals with liver or kidney issues, or those on medications that affect ammonia levels, should consult a doctor before taking ornithine.


Whether you're an athlete, an overworked professional, or someone looking for immune & anti-aging benefits, Ornithine may have something to offer you.

Ornithine is an often-overlooked amino acid that offers a variety of health benefits. Consult your healthcare provider for personalised advice or a Mr Supplement professional, especially if you're considering long-term use.


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)
Grimble GK. Adverse gastrointestinal effects of arginine and related amino acids. J Nutr. (2007)
Mutch BJ, Banister EW. Ammonia metabolism in exercise and fatigue: a review. Med Sci Sports Exerc. (1983)
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)
Sugino T, et al. L-ornithine supplementation attenuates physical fatigue in healthy volunteers by modulating lipid and amino acid metabolism. Nutr Res. (2008)

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