what is the difference between tryptophan and l-tryptophan

Tryptophan is an essential amino acid, but it exists in two forms: L-tryptophan and D-tryptophan. The L-form is the natural, biologically active version that your body uses to produce serotonin, melatonin, and proteins.

When people refer to “tryptophan” in food or supplements, they’re almost always talking about L-tryptophan. The D-form is not commonly used by the body and has little biological role.