• Gamma-aminobutyric Acid
The substance gamma-aminobutyric acid (GABA) is a neurotransmitter, a chemical used by the human nervous system to send messages and modulate its own function. GABA acts in an inhibitory manner, tending to cause nerves to “calm down.” Drugs in the benzodiazepine-receptor-agonist (BzRA) family (a family that includes true benzodiazepines such as valium, as well as related drugs such as Ambien or Lunesta) exert their effect by facilitating the ability of GABA to bind to receptor sites in the brain. This in turn leads to relaxation, relief from anxiety, induction of sleep, and suppression of seizure-activity.
Unfortunately, when GABA is taken orally, GABA levels in the brain do not increase, presumably because the substance itself cannot pass the blood-brain barrier and enter the central nervous system. ]]>1]]> For this reason, oral GABA supplements cannot replicate the effect of tranquilizing drugs, even though they work through a GABA-related mechanism. GABA supplements can affect the peripheral nervous system, however, as well as any other part of the body not protected by the blood brain barrier. Some evidence suggests that orally ingested GABA might cause physiological changes that lead to benefit for hypertension.
GABA is not a required nutrient and it is not found to any extent in food. However, certain probiotics in the Lactobacillus family can be induced to produce GABA as they ferment milk and soy products. 8]]> GABA supplements can also be created entirely synthetically.
In the best designed study of GABA for reducing blood pressure (described below), the dosage used was 10 mg daily.
Much higher dosages are sometimes recommended by alternative practitioners for treating anxiety or insomnia, as high as 1000 mg daily, in the (probably vain) hope that some tiny amount of this orally ingested GABA might make it into the brain.
In the best of the human trials, 39 people with mild hypertension were given either a fermented milk product providing GABA at a dose of 10 mg daily, or placebo, for 12 weeks. ]]>1]]> The results indicated that GABA modestly decreased blood pressure levels. However, this study was small and suffered from significant problems in design. Additional research will be necessary before GABA can be considered an effective treatment for high blood pressure.
3. Hayakawa K, Kimura M, Kasaha K, et al. Effect of a gamma-aminobutyric acid-enriched dairy product on the blood pressure of spontaneously hypertensive and normotensive Wistar-Kyoto rats. Br J Nutr. 2004;92:411-417.
4. Hayakawa K, Kimura M, Kasaha K, et al. Effect of a gamma-aminobutyric acid-enriched dairy product on the blood pressure of spontaneously hypertensive and normotensive Wistar-Kyoto rats. Br J Nutr. 2004;92:411-417.
6. Yamakoshi J, Fukuda S, Satoh T, et al. Antihypertensive and natriuretic effects of less-sodium soy sauce containing gamma-aminobutyric acid in spontaneously hypertensive rats. Biosci Biotechnol Biochem. 2007;71:165-173.
7. Hirata H, Kimura M, Nakagawa S, et al. Hypotensive effect of fermented milk containing gamma-aminobutyric acid (GABA) in subjects with high normal blood pressure. Journal of the Japanese Society for Food Science and Technology. 2004;51:79-86
8. Park KB, Oh SH. Production of yogurt with enhanced levels of gamma-aminobutyric acid and valuable nutrients using lactic acid bacteria and germinated soybean extract. Bioresour Technol. 2007;98:1675-1679.
Last reviewed April 2009 by EBSCO CAM Review Board]]>
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