Phenylalanine is an essential amino acid. Phenylalanine has got immense metabolic role in the body. It is ketogenic as well as glycogenic. Phenylalanine is initially but irreversibly hydroxylated to tyrosine. Tyrosine then undergoes series of metabolic changes leading to the formation of hormones epinephrine, nor epinephrine, thyroxin and tri-iodothyronine. It is not synthesized in the body but in the microorganisms it is synthesized.

Phenylalanine may undergo bacterial breakdown in the intestine by the bacterial enzyme with the formation of phenyl acetic acid. This phenyl acetic acid may be converted into benzoic acid. These toxic substances are absorbed and detoxicated in the liver. Like all other amino acids, phenylalanine also takes part in the synthesis of tissue protein.

It is available in three chemical forms: L-phenylalanine, the natural form of phenylalanine found in proteins throughout the body; (2) D-phenylalanine, a mirror image of L-phenylalanine that is synthesized in a laboratory; and (3) DL-phenylalanine, a combination of the previous two forms.

Sources of phenylalanine

L-phenylalanine is found in most foods that contain protein such as beef, poultry, pork, fish, milk, yogurt, eggs, cheese, soy products (including soy protein isolate, soybean flour, and tofu), and certain nuts and seeds.

Banana is also a rich source of phenylalanine.

The artificial sweetener aspartame is also high in phenylalanine.

D-phenylalanine is synthesized in the laboratory is not found in food.

Benefits of phenylalanine

D-phenylalanine may help reduce chronic pain associated with certain health conditions by stimulating nerve pathways in the brain that control pain

D-phenylalanine may improve rigidity, walking disabilities, speech difficulties, and depression associated with Parkinson's disease

Evidence suggests that combining L-phenylalanine (oral and topical) with UVA radiation for people with vitiligo (a condition characterized by irregular depigmentation or white patches of skin) may lead to some darkening or repigmentation of the whitened areas, particularly on the face.

Phenylalanine is also used to give relief to the patients suffering from depression. This is thought to be due to enhanced production of brain chemicals such as dopamine and nor epinephrine.

Phenylalanine acts as an analgesic. It also acts as an appetite suppressant by administrating the release of an intestinal hormone that signals the brain to feel satiated after eating. As an analgesic, it has been shown to decrease back pain, toothaches, and pain associated with migraine headaches.

It has also been used to treat attention deficit disorder, fatigue, Parkinson’s disease and premenstrual syndrome.

Deficiency symptoms of phenylalanine

Symptoms of phenylalanine deficiency include confusion, lack of energy, decreased alertness, decreased memory, and diminished appetite.

Its deficiency can also lead to stunted growth, apathy, muscle loss, and weakness.

A rare metabolic disorder called phenylketonuria (PKU) occurs in people who are missing an enzyme that is needed to properly metabolize phenylalanine. Symptoms of PKU, which tend to appear between three and six months of age, include eczema, developmental delay, an abnormally small head, and hyperactivity. If it is not treated before three weeks of age, PKU can cause severe, irreversible mental retardation

Symptoms of high intake

Doses in excess of 5,000 mg a day may be toxic and can cause nerve damage.

High quantities of DL-phenylalanine may cause mild side effects such as nausea, heartburn, and headaches.

Most consumers don't know that too much Phenylalanine is a neurotoxin and excites the neurons in the brain to the point of cellular death.

Emotional and behavioral disorders can all be triggered by too much Phenylalanine in the daily diet.

Phenylalanine can cause irreversible brain damage and death, especially when used in high quantities or during pregnancy.

Excessive amounts can also lead to hypertension and/or migraine headaches.

Daily requirement

Birth to 4 months: 125 mg per kilogram of body weight per day

Children 5 months to 2 years: 69 mg per kilogram of body weight per day

Children 3 to 12 years: 22 mg per kilogram of body weight per day

The combination of oral and topical phenylalanine (together with ultraviolet light) has been used to treat children with vitiligo. Physician would determine the dose and appropriate length of time to continue the therapy.

Teenagers and adults: 14 mg per kilogram of body weight per day

Some experts suggest that adults may need as much as 39 mg per kilogram of body weight per day for general health and doses as high as 50 to 100 mg per kilogram have been used in studies of those with vitiligo. The most common amounts used range from 750 to 3,000 mg per day for adults.

Other points

People with PKU and women who are lactating or are pregnant should not take phenylalanine supplements.

DL-phenylalanine may cause symptoms of anxiety, jitteriness, and hyperactivity in children. Children with ADHD may need to avoid foods containing aspartame, which is made from phenylalanine.

Patients already taking antidepressants should not supplement with phenylalanine.

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