Amino Acids - Introduction - L vs. D

When reading amino acid listings off multi-amino acid complexes or protein powders, you will almost always see each acid preceded by an "L" or "D". These letters refer to the orientation of the amino acid molecule.

"D" stands for "Dextro" and is Latin for "right". L stands for "Levi" and is Latin for "left". D and L aminos are mirror images of each other. The two terms indicate the direction of the rotation of the spiral that is the chemical structure of the molecule.

Proteins in animal and plant tissue are made from L- forms of amino acids. This excludes the amino acid L-Phenylalanine, which is prepared in the form DL-Phenylalanine (a mix of both D and L forms). Typically, DL-Phenylalanine is used as a painkiller I supplementation.

"D" is often a synthetic form of an amino acid while L is the more natural form. L- amino acids are also most compatible with human biochemistry.