Phenylalanine is an essential amino acid, which can be obtained from eating almonds, avocado, bananas, beans, brewer’s yeast, cheese, corn, cottage cheese, dairy products, eggs, fish, legumes, lima beans, meat, nuts, peanuts, pickled herring, pumpkin seeds, seafood, seeds, sesame seeds, soy, whey, and whole grains. Once inside the body phenylalanine is converted into the amino acid tyrosine, which is then converted into the neurotransmitters L-dopa, norepinephrine, and epinephrine. Phenylalanine governs the release of the hormone cholecystokinin (CCK) that signals the brain to feel satisfied after eating.

Phenylalanine is used to treat a variety of medical problems. Because some antidepressants work by raising norepinephrine levels phenylalanine has been used to treat depression, with varying degrees of success. D-phenylalanine has been suggested as a treatment for chronic pain caused by rheumatoid arthritis, muscle pain, and osteoarthritis, as It blocks enkephalinase, an enzyme that may act to increase pain levels in the body. There is some evidence to support the use of phenylalanine to alleviate chronic pain, although it has not been clinically proven. Some studies have suggested that the various forms of phenylalanine may be useful as a treatment for vitiligo (a disease characterized by abnormal white blotches of skin due to loss of pigmentation), when used in combination with UV light therapy.

Symptoms and signs of phenylalanine deficiency include: low serum levels of essential blood proteins, apathy, loss of pigmentation in hair, edema, lethargy, liver damage, muscle loss, fat loss, skin lesions, weakness, and slowed growth in children.

When used as a treatment for depression, the initial dose of L-phenylalanine is typically 500mg per day; the dose is then gradually increased to 3-4g daily. However, some people may suffer side effects at doses of 1.5mg and above. D- or DL-phenylalanine can also be used as a treatment for depression, however the typical dosage is much lower at 100-400mg per day For the treatment of chronic pain doses of Dphenylalanine can be as high as 2.5g.

Not established, however doses of 1.5g and above can cause side effects.

Phenylalanine does not generally cause side effects, however daily doses of approximately 1.5g and above have been reported to cause anxiety, headaches, and mildly elevated blood pressure. People who suffer from the metabolic disease phenylketonuria (PKU) should avoid all forms of phenylalanine (L-phenylalanine, Dphenylalanine, and DL-phenylalanine). Phenylalanine can cause potentially dangerous hypertension when taken with monoamine oxidase inhibitors (MAO’s). It should also not be taken alongside the amino acid tyrosine.

There is some evidence to suggest that using phenylalanine in combination with antipsychotic drugs may increase the risk of developing the movement disorder tardive dyskinesia. As with other amino acids, phenylalanine may interfere with the absorption and action of the anti-Parkinson’s drug levodopa. People with kidney disease or liver disease should consult their doctor before taking phenylalanine.