Amino acid

L Taurine

Taurine is an amino acid your body makes and stores heavily in muscle tissue — it's not a stimulant, despite showing up in energy drinks. Inside muscle cells it helps regulate calcium, which controls the strength of each contraction, and it helps cells hold onto water and stay balanced during hard efforts. Research in athletes links taurine with better endurance and less exercise-induced muscle damage. It's naturally found in meat and fish, and it's one of the most-studied ingredients in sports nutrition.