What do the letters “L” and “D” stand for in front of the amino acid names?

Amino acids exist in two types – L- and D-, each of which is a mirror image of the other. Scientists and biochemists call them isomers. And the letters “L” and “D” help determine which of the mirror types each acid belongs to. L- stands for levo (Latin for left) and D- stands for dextra (right). These terms represent the directions of rotation of the helix, which represents the structure of a given molecule.

In a word, amino acids of the “L” class are more compatible and similar to the biochemical processes of the human body, and for this reason they are recommended for athletes to include in their diet.

Try to avoid foods containing “D” amino acids, especially if they are represented by several species at the same time. For example, the class “L” and “D” include phenylalanine and methionine, these amino acids are biologically active. This means that both of them can be used in the human body.

Finally, it should be noted that an amino acid such as glycine does not have its own isomer. That is why its name is never preceded by the letters “L” or “D”.