What does it do? Ornithine, an amino acid, is manufactured by the body when another amino acid, arginine, is metabolized during the production of urea (a constituent of urine). Animal research has suggested that ornithine, along with arginine, may promote muscle-building activity in the body by increasing levels of anabolic (growth-promoting) hormones such as insulin and growth hormone. However, most human research does not support these claims at reasonable intake levels. One study that did demonstrate increased growth hormone with oral ornithine used very high amounts (an average of 13 grams per day) and reported many gastrointestinal side effects.

In clinical studies on people hospitalized for surgery, generalized infections, cancer, trauma, or burns, supplementation with ornithine has been reported to produce several beneficial effects. A double-blind trial evaluated the effects of ornithine supplementation in elderly people recovering from acute illnesses. Those who took 10 grams of ornithine per day for two months had marked improvement in appetite, weight gain, and quality of life..

Ornithine has been shown to be beneficial in people with hepatic encephalopathy (brain abnormalities) due to liver cirrhosis. In a double-blind trial, people with cirrhosis and hepatic encephalopathy received either 18 grams per day of L-ornithine or a placebo for two weeks. Those taking the ornithine had significant improvements in liver function and blood tests compared to those taking the placebo.

Preliminary and controlled studies of people with severe burns showed that supplementation with 10-30 grams of ornithine per day significantly improved wound healing and decreased the length of hospital stays.

Where is it found? As with amino acids in general, ornithine is predominantly found in meat, fish, dairy, and eggs. Western diets typically provide 5 grams per day. The body also produces ornithine.

Ornithine has been used in connection with the following conditions:

• Liver cirrhosis
• Recovery from illness
• Athletic performance (for body composition and strength)

Who is likely to be deficient? Since ornithine is produced by the body, a deficiency of this nonessential amino acid is unlikely, though depletion can occur during growth or pregnancy, and after severe trauma or malnutrition.

How much is usually taken? Most people would not benefit from ornithine supplementation. In human research involving ornithine, 5-10 grams are typically used per day, sometimes combined with arginine.

Are there any side effects or interactions? No side effects have been reported with the use of ornithine, except for gastrointestinal distress with intakes over 10 grams per day.