Threonine, also known as Thr amino acid, is an essential amino acid that is used in the biosynthesis of proteins in the human body. Threonine is abundant in meats but isn’t as common in fruits and vegetables.The “L” in L-threonine refers only to the orientation of the molecule. L-threonine is effectively the same as D-threonine. Threonine (Thr amino acid) has a wide range of health benefits. It fortifies immune function, promotes healthy liver function, and supports the joints, connective tissue, and bones.* Threonine also supports the nervous system and contributes to healthy mood and sleep.** These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.