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•NOTE: This summary also covers compounds related to GABA – such as GHB, GBL and BD – which are considered illegal/unapproved drugs (not dietary supplements) by the Food and Drug Administration 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.
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. A related compound known as GHB (gamma-hydroxybutyric acid) differs from GABA only by substitution of GABA’s amino group with a hydroxyl (OH) group – making GHB able to cross into the brain. As such, products containing GHB have been promoted as supplements to increase growth hormone levels, aid recovery from exercise and promote relaxation and sleep.
GABA and GHB appear to be readily interconvertible in the brain and a number of chemically related compounds, such as GBL (gamma-butyrolactone), BD (1,4-butanediol) and furanone (2,3H-furanone di-hydro) are rapidly converted in the body into GHB.
The Food and Drug Administration (FDA) and the National Institute on Drug Abuse (NIDA) consider GHB and related compounds (GBL, BD, furanone) to be dangerous unapproved drugs due to their tendency to cause seizures and other adverse side effects. GABA, however, is classified as an amino acid which is legal for use as a dietary supplement.
Scientific Support The predominant effects of GHB are sedative. At low doses, GHB can relieve anxiety and produce relaxation – as the dose increases, however, the sedative effects result in sleep and eventual coma or death. GHB is one of a number of drugs implicated as “date rape” drugs for its effects as a central nervous system depressant. GHB also stimulates the release of growth hormone from the anterior pituitary gland – but no studies have ever shown GHB to result in positive changes in body fat levels, muscle mass or strength. Whether or not GHB works is sort of a moot point – as the FDA banned over-the-counter sale of GHB in 1990 – but it is still available in various forms (GBL, BD, furanone) in illegal dietary supplements and on the black market.
Although GABA can be converted into GHB in the brain, and both appear to have power actions in certain regions of the brain, it is unclear whether orally administered GABA is converted to GHB. It does appear, however, that pituitary growth hormone release is partly regulated by blood levels of GABA.
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.
Studies which have examined glutamate supplements (glutamate can be converted into GABA) in athletes have shown a suppression of serum GH levels during exercise in cyclists receiving glutamate/arginine supplements. Another study found 10 grams of oral glutamic acid to stimulate the secretion some pituitary hormones (prolactin and cortisol), but no effect was seen on GH levels.
Although the chemical structure of GABA and GHB are similar, we are not aware of any adverse events associated with GABA-containing dietary supplements. GHB, however, is a far different story. Despite its presence in a wide variety of dietary supplements, the FDA considers it to be an illegal/unapproved drug – and not a supplement ingredient. As such, the FDA has moved to remove such products from the marketplace – and with good reason.
GHB-containing products have been associated with a number of adverse side effects related to the dose of GHB. Low doses of GHB (0.5-1.5 grams) typically induce feelings of relaxation similar to mild alcohol intoxication, while medium doses (1-2.5 grams) increase muscle relaxation and cause physical disequilibrium and loss of coordination. High doses of GHB (above 2.5 grams) result in nausea, vomiting, and drowsiness as well as more serious adverse effects such as depressed breathing, bradycardia (slow heart rate), coma, and even death. Alcohol and other drugs with central nervous system depressant effects are known to compound the effect of GHB.
••Toxic reactions have also been reported for supplement products containing GBL, BD and furanone.
As it is currently promoted, GABA supplements do not appear to be particularly effective in stimulating growth hormone synthesis/secretion or promoting relaxation. The majority of commercially available supplements provide GABA in levels of 250-750mg – far below the several grams per dose shown to be effective in influencing growth hormone metabolism.
When it comes to GHB and its various chemical cousins – the fact that the FDA considers them illegal drugs just about says it all.
Doses of GABA as high as 5 grams per dose are recommended within hard-core bodybuilding circles to stimulate spikes in plasma growth hormone levels, but smaller doses of 1-2 grams are probably more realistic. Doses are typically taken on an empty stomach prior to sleep.
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