Ornithine alpha-ketoglutarate (OKG) is manufactured from two amino acids, ornithine and glutamine. These amino acids are called “conditionally essential.” This means that ordinarily one does not need to consume them in food because the body can manufacture them from other nutrients. However, during periods of severe stress, such as recovery from major trauma or severe illness, the body may not be able to manufacture them in sufficient quantities, and may require an external source.
Ornithine and glutamine are thought to have anabolic effects, meaning that they stimulate the body to build muscle and other tissues. These amino acids also appear to have anti-catabolic effects. This is a closely related but slightly different property; ornithine and glutamine appear to block the effect of hormones that break down muscle and other tissues (catabolic hormones).
Evidence suggests that use of OKG (and related amino acids) may offer benefits for hospitalized patients recovering from serious illness or injury.
Based on these findings (and a leap of logic), OKG has been extensively marketed as a sports supplement for helping to build muscle. However, the fact that OKG helps seriously ill people build muscle does not mean that it will have the same effect in athletes, and there is no direct evidence to indicate that it does.
The amino acids that make up OKG are found in high-protein foods such as meat, fish, and dairy products. Supplements are available in tablet or pill form.
A typical dose of OKG is 5 to 25 g daily. It may be necessary to increase dosage slowly to avoid digestive upset.
OKG may play a role in the treatment of individuals recovering from severe physical trauma.
When the body experiences severe trauma—such as injury, major surgery, or burns—it goes into what is called a catabolic state. In this temporary condition, the body tends to tear itself down rather than build itself up. The catabolic hormone cortisone plays a major role in inducing catabolism. In the catabolic state, the body fails to utilize protein found in the diet, and high levels of protein breakdown products appear in the urine. Calcium levels in urine also rise, as bones begin to weaken.
The opposite of a catabolic state is an anabolic state, in which the body tends to build itself up. Studies of hospitalized patients recovering from severe illnesses or injuries suggest that OKG blocks the catabolic effects of cortisone and also directly stimulates anabolic activity.4-10 It is not clear how OKG accomplishes this. It may directly affect the enzymes involved in hormone metabolism. Another possibility is that OKG may increase levels of growth hormone (an anabolic hormone), at least when it is taken in high enough doses (12 mg a day or more).11-13 It has also been suggested that OKG increases insulin release, which would have anabolic effects; however, this has been disputed.14
Based on these findings, OKG has become popular as a bodybuilding supplement. However, there are no reported double-blind studies of OKG alone as a sports supplement. One study evaluated a combined arginine and ornithine supplement and found some evidence of benefit.15
Because it is simply ornithine and glutamine, OKG is presumably safe. However, high doses (over 5 to10 g) can cause diarrhea and stomach cramps. The maximum safe dosages for young children, women who are pregnant or nursing, or those with serious liver or kidney disease have not been established.
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16. Kircheis G, Wettstein M, Dahl S, et al. Clinical efficacy of L-ornithine-L-aspartate in the management of hepatic encephalopathy. Metab Brain Dis. 2002;17:453–462.
17. Jiang Q, Jiang XH, Zheng MH, et al. L-Ornithine-l-aspartate in the management of hepatic encephalopathy: A meta-analysis. J Gastroenterol Hepatol. 2008 Sep 24.
Last reviewed July 2012 by EBSCO CAM Review Board
Last Updated: 7/25/2012
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