*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.
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. 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
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
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
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
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
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.
1. Adverse events associated with ingestion of
gamma-butyrolactone--Minnesota, New Mexico, and
Texas, 1998-1999. MMWR Morb Mortal Wkly Rep. 1999
2. Cash CD. Gamma-hydroxybutyrate: an overview of
the pros and cons for it being a neurotransmitter
and/or a useful therapeutic agent. Neurosci Biobehav
Rev. 1994 Summer;18(2):291-304.
3. Chin MY, Kreutzer RA, Dyer JE. Acute poisoning
from gamma-hydroxybutyrate in California. West J
Med. 1992 Apr;156(4):380-0-4. 4. Davis LG.
Fatalities attributed to GHB and related compounds.
South Med J. 1999 Oct;92(10):1037.
5. Feigenbaum JJ, Howard SG. Gamma hydroxybutyrate
is not a GABA agonist. Prog Neurobiol. 1996
6. Iven VG. Recreational drugs. Clin Sports Med.
7. Plantey F. GHB and GABA. Am J Psychiatry. 1977
8. Rosen MI, Pearsall HR, Woods SW, Kosten TR.
Effects of gamma-hydroxybutyric acid (GHB) in
opioid-dependent patients. J Subst Abuse Treat. 1997
9. Sanguineti VR, Angelo A, Frank MR. GHB: a home
brew. Am J Drug Alcohol Abuse. 1997
10. Tunnicliff G. Significance of
gamma-hydroxybutyric acid in the brain. Gen
Pharmacol. 1992 Nov;23(6):1027-34.
11. Tunnicliff G. Sites of action of
gamma-hydroxybutyrate (GHB)--a neuroactive drug with
abuse potential. J Toxicol Clin Toxicol.
12. Vescovi PP, Di Gennaro C. Failure of
gammahydroxy butyric acid to stimulate growth
hormone secretion in cocaine addicts. Neuropeptides.
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