D-Threonine
This amino acid supports central nervous, cardiovascular, liver, and immune system functioning - just to name a few. Moreover, it helps in the synthesis of glycine and serine which, in their turn, assist in the production of collagen, elastin, and muscle tissue. In addition, Threonine aids building strong bones and tooth enamel and speeds up a wound healing process after trauma or surgery by boosting up the immune system.