A chemical produced by the brain. GABA plays an important role in the central nervous system. It regulates muscle tension, and some supplement formulas include GABA to provide a calming effect or to promote muscle growth.

There is no evidence to show that GABA supplements can function in this manner. Because GABA needs to cross the blood-brain barrier in order to affect the brain, many researchers believe that supplementation is not biologically possible with the small doses found in most over-the-counter pills. Some users may report a calming sensation due to the placebo effect, although there is not enough research to definitively declare whether GABA is effective in any way.

GABA is naturally produced by the body and is considered a safe ingredient in normal doses.