The rate-limiting essential amino acid for serotonin synthesis — it must be obtained through the diet. Dietary tryptophan directly determines serotonin production. Serotonin then converts to melatonin (via the ASMT enzyme) in a methylation-dependent step requiring SAMe. Provides the precursor supply layer; the upstream methylation stack (SAM-e, Methylated Multi) must be intact to complete serotonin → melatonin conversion.
