The “D” isomer of L-phenylalanine, an essential amino acid. D-phenylalanine has been used as an alternative treatment for pain relief, on the strength of its alleged ability to inhibit enkephalin breakdown. The supporting studies have been described as “weak and contradictory,” however, with negative results in humans and primates. It’s also claimed that d-phenylalanine increases brain phenethylamine concentration, but this is disputed by other research.
May be included in supplements as a part of “DLPA”, or DL-phenylalanine, which is a 50-50 mixture (i.e., a “racemic” mixture) of the 2 isomers.