GABA (gamma-aminobutyric acid) is an amino acid that functions as a neurotransmitter in the brain. GABA is synthesized in the brain from another amino acid, glutamate, and functions as an inhibitory neurotransmitter – meaning that it blocks nerve impulses.
In the body, GABA is concentrated in the hypothalamus region of the brain and is known to play a role in the overall functioning of the pituitary gland – which regulates growth hormone synthesis, sleep cycles, and body temperature.
Claims
- Increases growth hormone levels
- Induces relaxation / sleep
- Promotes muscle recovery
- Relieves anxiety / Promotes feelings of well-being
As a dietary supplement, GABA is typically promoted to bodybuilders and other athletes as a nutrient to help stimulate secretion of growth hormone, decrease body fat levels and increase lean muscle tissue. The problem, however, is that GABA does not cross the blood-brain barrier, so it can not get into the brain where it is active.
Many supplement marketers cite a single obscure Italian study as evidence that GABA increases growth hormone (GH) secretion in athletes. The study, which was conducted over 20 years ago, was carried out in fewer than 20 subjects, and while it did show an increase in blood levels of GH, it has yet to be replicated by other scientists.
In more recent studies (in sheep), intravenous administration of GABA resulted in a rapid increase in plasma GH levels, while direct administration of GABA into the brain produced a significant increase in GH release. In other studies (in mice), increased concentrations of GABA in the systemic circulation have been linked to impaired liver repair.
