The amino acid gamma aminobutyric acid is a neurotransmitter in humans. Its role is to decrease electrical activity in the brain and thus produces a calming and relaxing effect. Most foods contain low levels of GABA, but higher amounts are present in fermented foods produced by lactic acid producing bacteria. Studies have indicated that dietary source of GABA may have significant anxiolytic effects in humans. For example, in one study, researchers administered 100 mg of GABA to individuals and then assessed their brain wave pattern. The GABA caused a significant decrease in beta waves in the brain and a significant increase in alpha waves. Beta waves are associated with active, busy or anxious thought patterns, whereas alpha waves are associated with calmness and relaxation to thought patterns. Therefore GABA not only reduces anxiety but also actively promotes calmness and relaxation. This is in line with the role of GABA an an inhibitory neurotransmitter in the brain and central nervous system.
In one human study, researchers administered 100 mg of GABA as a supplement to healthy human subjects and then exposed them to experimental stress. The results of the study showed that perceived stress of the subjects was significantly lessened by the taking of the GABA supplement. In addition, declines in alpha wave activity caused by the stress were attenuated by the administration of GABA, suggesting that the GABA had beneficial effects on the development of anxiety.
Interestingly the same study also investigated the effects of 200 mg of L-theanine on the brain wave activity of human subjects. In this regard, L-theanine was also able to increase the alpha wave pattern in the brains of the subjects, but not to the same extent as GABA. Further, L-theanine was also able to decrease beta waves patterns in the brains of the subjects, but again, to a lesser extent that the GABA. Therefore GABA was able to improved the alpha to beta brain wave ratio more favourably compared to the L-theanine. The same authors also investigated the effects of GABA on immunity is subjects suffering from anxiety. The subjects, who were all diagnosed clinically with acrophobia, where exposed to their fear by being asked to walk across a suspension bridge. This caused the subjects to have significant reductions in immunoglobulin A content of their saliva, an indication of immune suppression. However, a GABA supplement was able to significantly attenuate the fall in immunoglobulin levels experienced by the subjects.
Supplements of GABA may also have neuroprotective effects against exposure to stress. For example fatigue in healthy subject exposed to work stress was significantly lessened by administration of 50 mg of GAGA in a drink. In addition, the salivary levels of chromogranin A and cortisol, two markers of stress, were significantly lessened by administration of 25 mg and 50 mg of GABA as a drink. The subject receiving 50 mg of GABA also performed better on a test of mental arithmetic compared to a control group. Therefore GABA supplements may have significant neuroprotective effects against stress that may enhance mental performance.
Interestingly, the amino acid L-theanine, a component of tea, may exert its effect through modulation of the GABA system. For example, in rats, it has been observed that L-theanine is able to significantly increase brain levels of GABA. This may explain the calming effects of L-theanine, and why it is able to increase alpha waves and decrease beta waves in the brains of humans. That L-theanine functions through activation of the GABA system is further evidence by the fact that L-theanine produces cognitive and memory improvements in humans. However, these effects can be inhibited by administrations of bicuculline, a drug that is able to antagonise the GABAA receptor. Therefore this suggests that the effects of L-theanine may occur through activation of the GABAA receptor in the brain and that L-theanine acts as a GABAergic compound through activation of the GABA neurotransmitter system. Both dietary L-theanine and GABA may therefore be able to cross the blood brain barrier and activate the GABA system.
Supplemental GABA has been shown to favourably regulate blood pressure. For example, in one study, in mildly hypertensive subjects, the systolic blood pressure decreased by 17.4 mmHg and diastolic blood pressure decreased by 7.2 mmHg over 12 weeks following consumption of a fermented milk enriched with GABA. The milk had been fermented by Lactobacillus casei and Lactobacillus lactis to increase the GABA content to 10 to 12 mg per 100 mL. Some of the blood pressure lowering effect may come from activation of peripheral blood pressure receptors by the GABA. However, it could be that the relaxation effect of GABA are also able to centrally regulate blood pressure by promoting a general anxiolytic effect.
In another study, researchers administered high GABA chocolate to subjects who were experimentally exposed to stressful conditions. The chocolate contained 0.28 % GABA and the subjects consumed 10 grams of chocolate which provided 28 mg GABA, a relatively small amount. Exposure to stress caused significant elevations in chromogranin A concentrations in the saliva of the subjects. Salivary chromogranin A elevations in saliva are used as a marker for stress in humans. However, the increase in chromogranin A were attenuated by administration of GABA. In addition, the chromogranin A levels returned to baseline more quickly following administration of GABA. Supplemental and dietary GABA may also have beneficial effects in the periphery including a lowering of blood pressure, which has been widely reported. This may occur by activation of peripheral GABA receptors. However, as GABA reduces perceived stress, blood pressure falls could also be an artifact of the anxiolytic effects of GABA in the brain.
Eat Well, Stay Healthy, Protect Yourself
RdB
