It has been reported that GABA can enhance GH secretion in response to exercise. In one study, subjects were given either 3 grams of GABA or a placebo, and as part of the study, they performed an intense 15-minute resistance routine that included the chest press, pulldown, flye, seated row, shoulder press, biceps curl, triceps extension, leg press, leg curl, leg extension, and calf raise. GABA plus exercise produced significantly higher levels of GH than exercise plus placebo, both at various times after consumption and in terms of totals secreted. GH response after exercise plus GABA was approximately 200% greater than exercise with placebo—30 minutes after exercise stopped.
In addition to its GH-enhancing effects, GABA also has anti-anxiety effects, which can help bodybuilders sleep when they are dieting and cortisol levels are higher. Previously, the effect of orally administered GABA on relaxation and immunity during stress has been investigated in humans. Two studies were conducted. The first evaluated the effect of GABA intake on the brain waves of 13 subjects. Electroencephalograms (EEGs) were obtained after three tests on volunteers who took in either water, GABA, or L-theanine. Sixty minutes later, it was shown that consuming GABA significantly increased alpha waves and decreased beta waves compared with water or L-theanine. These findings denote that GABA not only induces relaxation but also reduces anxiety. The second study was conducted to determine relaxant and anti-anxiety effects on immunity. Eight subjects with a fear of height were separated into two groups. All the participants were asked to cross a suspended bridge to stress them out. Immunoglobulin A (IgA-a marker of immune function) levels in their saliva were monitored during their bridge crossing. The placebo group showed a marked decrease in IgA, while the GABA group showed significantly higher levels. The report showed that GABA could work effectively as a natural relaxant within one hour of consumption. Finally, a more recent study published in the Journal of Amino Acids showed that GABA taken before mentally stressful stimuli alleviated that stress and induced a more relaxed brain state. Bodybuilders may want to consider taking GABA during a competitive diet to help them sleep and reduce mental stress.
Reference: A. Yoto et al., “Oral intake of γ-aminobutyric acid affects mood and activities of central nervous system during stressed condition induced by mental tasks,” Journal of Amino Acids, Dec. 2011 [e-published ahead of print].