Promote nervous system health as well as a positive well-being with Source Naturals Free Form L-Phenylalanine. An essential amino acid, l-phenylalanine is converted by the body into norepinephrine, a vital neurotransmitter and adrenal hormone. No yeast, dairy, egg, gluten, corn, soy, wheat, sugar, starch, salt, preservatives, or artificial color, flavor or fragrance.