Phenylalalin has been shown to improve the mood by stimulating the nervous system and therefore help to remain motivated.

It is also thought to increase the level of intelligence like Glutamine because it strengthens the memory.

Dopamine in the anterior pituitary increases adrenaline and neuradrenaline (epinephrine and neurrepinephrine) levels. They are necessary for the proper functioning of the nervous system.

It also helps absorb UV rays in sunlight; which in turn raises the body's vitamin D level.

It is also one of the amino acids that produce glutamine.

Phenylalanine is converted to tyrosine in the presence of phenylalanine hydroxylase enzyme and in the presence of tetrahydrobiyopterin coenzyme. Reactions starting when tyrosine is hydroxylated to 3,4 dihydroxyphenylalanine (DOPA) produce neurotransmitter substances and various hormones. As a result of genetic anomalies, some enzymes may be impaired and undesirable metabolites may accumulate in the body. Hyperphenylalaninemias (HPA) are formed as a result of mutation in the gene that forms the phenylalanine hydroxylase enzyme. The most common disease associated with HPA amino acid metabolism disorder is phenylketonuria (PKU). In PKU, tyrosine synthesis cannot occur due to deficiency of phenylalanine hydroxylase enzyme in the liver and phenylalanine metabolites accumulate in the blood.