Gamma-aminobutyric acid, or GABA, is a substance that bodybuilders and other athletes sometimes use when looking for a competitive edge. It is an amino acid that serves as a neurotransmitter in the brain. GABA is legal as a dietary supplement, though the U.S. Food and Drug Administration considers certain closely related compounds, including gamma-hydroxybutyric acid, or GHB, to be unapproved drugs.
GABA acts on the pituitary gland, which controls synthesis of growth hormone and also plays a role in body temperature and sleep cycles, according to Iron Magazine. Makers of GABA supplements promote them as increasing growth hormone levels, facilitating muscle recovery, relieving anxiety and inducing sleep. The results that athletes hope for are more lean muscle tissue and lower body fat levels.
GABA is of dubious value as a bodybuilding supplement, according to Iron Magazine. In order to act on hormone levels, it would need to enter the brain. But the supplements do not cross the blood-brain barrier. Thus, the magazine concludes that they "do not appear to be particularly effective in stimulating growth hormone synthesis/secretion or promoting relaxation."
GABA generally does not produce serious side effects, according to BodyBuildingForYou.com. It can sometimes cause tingling in the face and neck area. A mild, transient increase in breathing rate and heart rate is possible. If you are not taking it to relax or help with sleep, then its sedative action can also be considered a side effect.
Athletes usually take GABA orally, though intravenous administration is possible, as well. They consume it on an empty stomach once a day before bedtime, according to Iron Magazine. Hardcore bodybuilders sometimes take 5 g per dose, but 1 g or 2 g is more common. In fact, the magazine notes, a typical, commercially available GABA tablet contains 250 to 750 mg -- well under 1 g.
Use careful scrutiny when evaluating claims from supplement manufacturers. The FDA took one maker of GABA to task in March 2004 for stating that its products "stimulate the body's ability to secrete the powerful fat burning hormone hGH during sleep" and that "people taking GABA tend to lose excess body fat." In a warning letter, FDA officials informed the Clifton Park, N.Y.-based company Better Bodz that the statements about the InShape DreamShape products were "not supported by reliable scientific evidence."