Ornithine alpha-ketoglutarate (OKG) is a salt formed of two molecules of ornithine and one molecule of alpha-ketoglutarate. Studies in the medical field have shown that ornithine alpha-ketoglutarate preserve muscle protein synthesis and spares nitrogen.
OKG supplementation decreases muscle protein catabolism and/or increases synthesis, according to the metabolic situation. The anti-catabolic effect might not be from OKG alone. OKG increases the plasma concentrations of, for example, arginine, leucine, isoleucine, tyrosine, glutamine, proline, and ornithine. There are several studies that show these amino acids to have anabolic properties; hence, the anti-catabolic effect.
As far as I know there haven't been any studies on athletes and OKG. We have to relate to the medical studies. Some studies has shown OKG to increase growth hormone levels, but it is not known if this will help the athlete. The most interesting aspect of OKG is that it helps to increase the levels of glutamine in the muscle cells. As I mentioned in my article about glutamine, high glutamine levels have a very anti-catabolic effect, especially in people under severe stress such as hard training or fasten. Some studies have shown OKG to have positive effects on maintaining immune system health, this due to the increased amount of arginine in the blood stream. However, more data are necessary in order to find out in vivo the effect of ornithine on the immune system, which is influenced by many hormonal factors.
As with all supplements, the dosage varies depending on your weight (muscle mass), activity level and food intake. I recommend 10-20 grams a day. Take one half about an hour before training and the second half before bedtime. Take your OKG together with carbohydrates. No side effects have been reported from OKG supplementation when taken in recommended dosages. Higher dosages might cause stomach problems such as diarrhea.
OKG seems to be a good supplement for athletes during hard training and/or diet.