Gamma-aminobutyric acid, or GABA, is a neurotransmitter in the human body that helps control the firing of your nervous system. It mainly helps to inhibit how often your nervous system sends signals to your brain, producing a calming effect on the body. Many fitness supplement companies market GABA as being beneficial for muscle growth, but some of these claims are unsubstantiated by independent scientific research.

GABA and Growth Hormone

One of the primary reasons bodybuilders and athletes take GABA supplements is that some research indicates it may increase growth hormone levels in your body. According to the guide “Nutritional Concerns in Recreation, Exercise and Sports,” one study into GABA supplementation found that growth hormone levels increased within three hours of consuming a 5 g dose. Two follow up studies confirmed the results, however one study did show that taking an 18 g dose for four consecutive days inhibited the growth hormone response.

GABA and Stress

Stress can reduce how effective your body is at fighting off disease and how well your muscles repair after a hard workout. According to nutrition supplement expert Ray Sahelian, M.D., a 2006 study on GABA supplementation showed that subjects had a significant increase in alpha brain waves and a decrease in beta brain waves, indicating reduced stress levels and anxiety. Lowered stress levels may have some benefit to your sleep, so you are better rested for exercise.

Blood-Brain Barrier

One of the main issues with GABA supplementation is that the neurotransmitter must enter your brain to influence growth hormone or stress levels. Registered dietician Dr. Debra Goodwin of Jacksonville State University notes that GABA supplements do not readily transport from your bloodstream to your brain, and therefore heavy dosing of GABA would not guarantee an increase of it in your brain. The Langone Medical Center at New York University states that doses up to 1 g per day may be taken safely in the hopes that some of it makes it into your brain.

L-Glutamine

Because of the blood-brain barrier issue with GABA supplements, you may be able to increase how much GABA your body produces more effectively by consuming the essential amino acid L-Glutamine. A 2004 review of amino acid supplements published in the “Journal of Addictive Disorders” indicates that L-Glutamine readily passes through the blood-brain barrier. Once it enters your brain, it is converted to glutamic acid, which helps brain function, and also naturally increases your GABA levels.