Ornithine is a nonessential amino acid, meaning that it is naturally produced by the body. Synthesized from arginine, another amino acid, ornithine is used in the urea cycle. The primary benefit of ornithine is that it helps convert toxic ammonia into urea (also known as carbamide), a cleansing organic compound and waste product excreted in the urine. This process also removes excess nitrogen from the body.
As the body produces ornithine, deficiencies of this nutrient are unlikely in healthy people. In addition, ornithine is obtained through eating meat, fish, dairy and eggs. People who eat a vegan diet can have low levels of ornithine, as can malnourished individuals, pregnant women, children experiencing a growth spurt or those who recently suffered a severe trauma.
The most common use for ornithine supplements is for its reputed muscle-building benefits, along with its ability to promote the production of growth hormones and insulin. While there has been some evidence of these benefits in testing on animals, there isn't adequate supporting evidence of these ornithine benefits in humans. One study on humans by Bucci et al. (see Resources) indicated that ornithine may increase growth hormone and insulin production when supplemented at 13 grams daily, which is 3 grams higher than the maximum recommended dosage. However, as ornithine is not coded for in DNA, it has no role in protein synthesis, making claims that it can help build muscles dubious at best.
High doses of ornithine supplements have been show to benefit liver function, particularly in those suffering from cirrhosis of the liver (see citation by Stauch et al. in Resources). These doses were administered as high as 18 grams a day.
Ornithine has been show to have several benefits for the elderly. A study by Brocker et al. (see Resources) showed that supplements at 10 grams a day can slow the muscle degeneration associated with aging, bolster appetites, promote healthy weight gain and contribute to a general sense of well-being in older people.
Ornithine can speed recovery after surgery or from infections, burns, trauma and cancer treatments. Ornithine can also provide more energy via its role in synthesizing three other amino acids that fuel cells: proline, citrulline and glutamic acid.
Recommended ornithine supplement doses are from 5 to 10 grams daily. Higher doses frequently cause gastrointestinal distress. Ornithine is not reported to cause any other side effects, nor is it known to have any dangerous drug interactions. Benefits may manifest more readily when ornithine supplements are taken in conjunction with arginine supplements. Always check with your doctor before beginning an ornithine supplement regimen.