Phenylalanine is one of the nine essential amino acids and is required by the body to make proteins.* It can also be readily converted into the amino acid tyrosine, which forms part of the structure of the neurotransmitters dopamine and norepinephrine, which is important for the maintenance of a healthy nervous system.* Research suggests it may also help support healthy weight when taken before meals.* It was observed to reduce total food intake and believed to have this effect by increasing levels of the hormone cholecystokinin, which stimulates digestion and helps regulate appetite control.*