A 50/50 blend of the D- and L-forms of the amino acid phenylalanine;Phenylalanine is one of the few amino acids that can be utilized in its D- form;Researchers believe DPA inhibits the action of an enzyme that breaks down endorphins and enkephalins;DPA may extend the life of endorphins and enkephalins, and their positive influence on comfort levels;LPA is the precursor to two neurotransmitters that help support an alert state