Taurine

Taurine (2-aminoethanesulfonic acid) is not a true amino acid but an amino sulfonic acid abundantly present in the brain, heart, and skeletal muscle. Despite its association with energy drinks (where it was first isolated from bull bile in 1827), taurine functions as an inhibitory neuromodulator. It activates GABA-A receptors, glycine receptors, and extrasynaptic GABA-A receptors, producing calming effects. Taurine is also involved in bile acid conjugation, cell membrane stabilization, and calcium signaling. In sleep research, its GABAergic and glycinergic activity is studied for sleep onset and quality support. The body synthesizes taurine from cysteine, but synthesis declines with age.