Amino acids are building blocks of protein, used by your body to construct many different types of these essential compounds. But some amino acids, including one called L-ornithine -- or, more commonly, ornithine -- may have other important roles. L-ornithine is crucial for removal of bodily wastes, and some research also suggests this amino acid may help boost your energy level and provide your body with other significant benefits.
The Urea Cycle
When your cells break down nitrogen-containing compounds such as proteins, they produce ammonia as a byproduct. This can be toxic if not removed. In the urea cycle, liver cells convert ammonia into urea, a waste product eliminated by your kidneys -- ornithine is central to this process and gives the cycle its alternate name, the ornithine cycle. When a problem develops and ornithine can't participate effectively in the urea cycle, potentially serious conditions can result, including one called ornithine transcarbamylase deficiency. This rare inherited disorder occurs in 1 in 80,000 people. It interferes with the urea cycle, allowing ammonia to accumulate in the blood, and this can cause lack of energy, seizures or other symptoms.
Your kidneys convert ornithine into arginine, another amino acid that benefits your body in several ways. Arginine is a precursor for a compound called nitric oxide, which helps dilate your blood vessels when you require extra blood to your tissues. Arginine also helps your muscle cells produce creatine, a compound they need to contract. Research suggests that consuming extra ornithine can help promote physical strength and endurance. For example, a study published in the November 2008 issue of "Nutrition Research" found that healthy subjects who took extra ornithine experienced less exercise-induced fatigue than a placebo group. The authors concluded that ornithine promotes more efficient energy usage by cells, and they recommend it as an nutritional supplement to prevent fatigue.
Laboratory research suggests that L-ornithine may have other important and potentially beneficial functions in your body. A study published in the August 2002 issue of the "Journal of Surgical Research" found that supplementing laboratory animals with ornithine enhanced wound healing, an effect the authors attributed to quicker production of collagen, a compound important in forming new connective tissue. Another study in which laboratory animals consumed extra L-ornithine, published in the November 2011 issue of "Nutrition and Neuroscience," found that the amino acid crossed the blood-brain barrier and reduced anxietylike behavior in the animals, compared to controls. These promising results from laboratory studies still need confirmation in human subjects.
Ornithine is called a nonessential amino acid because your body can manufacture it. As part of the urea cycle, your liver cells produce ornithine from the amino acid arginine, which you consume in many different foods. Dietary sources of ornithine include meat, fish, eggs and dairy products, and especially good sources of arginine include turkey, peanuts, soybeans, egg whites and sesame seeds. L-ornithine supplements are also available from health foods stores and are generally considered safe, although no minimum effective dose has been established. If you have questions about L-ornithine, discuss them with your doctor.
Is This an Emergency?
- Memorial Sloan-Kettering Cancer Center: Arginine
- Elmhurst College Virtual Chembook: Urea Cycle
- Genetics Home Reference: Ornithine Transcarbamylase Deficiency
- Nutritional Research: L-Ornithine Supplementation Attenuates Physical Fatigue in Healthy Volunteers by Modulating Lipid and Amino Acid Metabolism
- Journal of Surgical Research: Effect of Supplemental Ornithinen on Wound Healing
- Nutrition and Neuroscience: Orally Administered L-Ornithine Elevates Brain L-Ornithine Levels and Has an Anxiolytic-Like Effect in Mice
- USDA National Nutrient Database: Arginine