L-arginine and L-ornithine, or simply arginine and ornithine, are two amino acids that share a lot in common in spite of one significant difference. Like most amino acids, arginine helps build proteins. Ornithine, on the other hand, doesn't participate in protein synthesis. Your body relies on both amino acids to function properly, and they work together -- as well as separately -- to ensure your health.
Ammonia is a byproduct formed during the metabolism of protein. Since ammonia is toxic, your body neutralizes and eliminates it through a process called the urea cycle. The cycle follows precise steps, with each one requiring specific substances to complete its part of the cycle. Arginine and ornithine are used in four of the five enzymes essential to these steps. While urea cycle disorders are often caused by genetic diseases, a deficiency of arginine or ornithine triggered by illness or stress can cause a small increase in ammonia levels in the blood, according to the Rare Diseases Clinical Research Network.
Boost Growth Hormone
Arginine and ornithine stimulate the release of human growth hormone, which may help build muscles. When a group of men took 7 grams of arginine prior to exercising, their blood levels of growth hormone increased more than the normal boost caused by exercise alone, according to an article in the September 2006 issue of the "Journal of Applied Physiology." A similar result was achieved when athletes took a combination of 3,000 milligrams of arginine and 2,200 milligrams of ornithine twice daily for three weeks. Their levels of growth hormone were significantly higher following exercise than those of the group who did not take supplements, according to an article in the April 2010 issue of the "Journal of Strength and Conditioning Research."
Lower Blood Pressure
Your body uses ornithine to synthesize arginine, then arginine is used to produce nitric oxide. Nitric oxide regulates smooth muscle contraction, which allows it to relax the muscles in blood vessels, according to NYU Langone Medical Center. When patients with high blood pressure took either 6 or 12 grams of arginine daily, blood pressure in the group treated with 12 grams dropped significantly, reported a study published in the "Medical Science Monitor" in May 2010.
Choose Top Sources
Your body produces arginine and ornithine, so they're not an essential part of your diet. However, they're conditional amino acids, which means your body needs more of them when you're sick or under stress and it may not be able to keep up with the demand. During those times, you may need to boost your consumption of arginine and ornithine, whether through foods or supplements. Good sources of both amino acids include fish, lean meat, eggs and dairy products. You can also get arginine from beans, brown rice, oatmeal, nuts and fish.
- National Urea Cycle Disorders Foundation: What Is a Urea Cycle Disorder?
- Gene Reviews: Urea Cycle Disorders Overview
- Rare Diseases Clinical Research Network: Urea Cycle Disease Overview
- Journal of Strength and Conditioning Research: Arginine and Ornithine Supplementation Increases Growth Hormone and Insulin-Like Growth Factor-1 Serum Levels After Heavy-Resistance Exercise in Strength-Trained Athletes
- Journal of Applied Physiology: Oral Arginine Attenuates the Growth Hormone Response to Resistance Exercise
- NYU Langone Medical Center: Arginine
- Medical Science Monitor: Evaluation of the Antihypertensive Effect of L-Arginine Supplementation in Patients With Mild Hypertension Assessed With Ambulatory Blood Pressure Monitoring
- Orthomolecular.org: Proteins/Amino Acids
- MedlinePlus: Amino Acids