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Phenylalanine quick review
Description: an essential amino acid, part of the composition of aspartame, normally converted to tyrosine in the body.
Health benefits: used to treated depression, rheumatoid arthritis and osteoarthritis, menstrual cramps, Parkinson's disease, vitiligo, and cancer.

Sources & dosage: eggs, milk, bananas, meat, beef, poultry, pork, fish, milk, yogurt, cheese, soy products. Typical consumption of dl-phenylalanine supplements is 375 mg to 2.25 grams daily.
Deficiency symptoms: confusion, emotional agitation, depression, decreased alertness, decreased memory, behavioral changes, decreased sexual interest, bloodshot eyes, and cataracts.
Side effects: large dose may cause nerve damage. Toxicity symptoms include increased blood pressure and emotional agitation, insomnia, headaches, and tyrosine toxicity.
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Phenylalanine is an essential amino acid that occurs as a constituent of many proteins and is normally converted to tyrosine in the body. Phenylalanine is part of the composition of aspartame, a common sweetener found in prepared foods (particularly soft drinks, and gum). Phenylalanine exists in two forms, the D- and L- forms. It has a phenyl side chain. L-phenylalanine is an electrically neutral amino acid found in proteins, coded for by DNA. Its mirror image, D-phenylalanine (DPA), can be synthesized artificially. DL-phenylalanine refers to a racemic mixture consisting of 50% D-phenylalanine and 50% L-phenylalanine. L-phenylalanine is an essential protein amino acid. D-phenylalanine is the enantiomer of L-phenylalanine. D-phenylalanine is a nonprotein amino acid, meaning that it does not participate in protein biosynthesis.

L-phenylalanine (LPA) serves as a building block for the various proteins that are produced in the body. L-phenylalanine can be converted to l-tyrosine (another amino acid) and subsequently to l-dopa, norepinephrine, and epinephrine. L-tyrosine produced from l-phenylalanine is a precursor in the synthesis of the neurotransmitters norepinephrine and dopamine, among other reactions. The conversion of l-phenylalanine to l-tyrosine is via the enzyme l-phenylalanine hydroxylase. L-phenylalanine is marketed as a nutritional supplement and used by some for its putative antidepressant activity. L-phenylalanine can also be converted (through a separate pathway) to phenylethylamine, a substance that occurs naturally in the brain and appears to elevate mood. The D-form of phenylalanine cannot be converted to tyrosine, but it can be converted to another compound called phenylethylamine which may have effects in elevating mood, treating depression and altering pain sensation.


Phenylalanine functions, uses, and health benefits

Phenylalanine is used to treated depression (elevates mood), rheumatoid arthritis and osteoarthritis (decreases pain/inflammation), menstrual cramps, Parkinson's disease (improves speech and rigidity), vitiligo (a skin pigment disorder), and
cancer (melanoma, tumor growth). L-phenylalanine is associated with nervous states and has anti-depressant properties. Phenylalanine is part of certain hormones in the body which affect moods e.g., melanotropin and endorphins etc. Phenylalanine is used in different biochemical processes to produce neurotransmitters, dopamine, norepinephrine, and epinephrine. Norepinephrine is believed to be in short supply in the brains of people who are depressed. By taking in extra phenylalanine, it is hoped the brain will make more norepinephrine. L-phenylalanine can promote high blood pressure in those predisposed to hypertension. In the liver, l-phenylalanine is involved in a number of biochemical reactions, including protein synthesis, the formation of l-tyrosine and oxidative catabolic reactions.

D-phenylalanine inhibits the metabolism of opiate-like substances called enkephalins in the brain. D-phenylalanine enhances the effects of pain killers. D-phenylalanine may help reduce chronic pain associated with certain health conditions by stimulating nerve pathways in the brain that control pain. DL-phenylalanine is effective in the treatment of chronic pain. Phenylalanine can promote the cell division of existing malignant melanoma cells. L-phenylalanine may also be useful in the treatment of vitiligo. 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 stimulates a particular hormone (cholecystokinin) in the body which causes suppression of the appetite. Phenylalanine also plays a role in energy production. It can be used to form glucose in the body which is needed for energy production.


Dietary sources of phenylalanine

Phenylalanine is found naturally in foods such as eggs, milk, bananas, and meat. L-phenylalanine is found in most foods that contain protein such as beef, poultry, pork, fish, milk, yogurt, cheese, soy products (including soy protein isolate, soybean flour, and tofu), and certain nuts and seeds. The artificial sweetener aspartame is also high in phenylalanine. Vegetables and juices contain small amounts of the free amino acid.


Phenylalanine dosage, intake

L-phenylalanine supplements as well as DL-phenylalanine supplements are available in the nutritional supplement marketplace. L-phenylalanine has been used in amounts up to 3.5 grams per day. Typical consumption of dl-phenylalanine supplements is 375 mg to 2.25 grams daily. Recommended dosages of phenylalanine vary depending on the health condition being treated. It’s necessary to seek medical advice before supplementation. Supplements are recommended 15 to 30 minutes before meals.


Phenylalanine deficiency

Deficiencies can occur if the enzyme that converts phenylalanine to tyrosine is absent. Phenylketonuria (PKU), a rare metabolic disorder, 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. A deficiency in diet would only occur with an extremely low protein intake. Symptoms of phenylalanine deficiency may include confusion, emotional agitation, depression, decreased alertness, decreased memory, behavioral changes, decreased sexual interest, bloodshot eyes, and cataracts. If not corrected by supplemental dietary phenylalanine and tyrosine, the deficiency may lead to restricted weight gain and stunted growth, osteopenia, anemia, alopecia, and even death.

Toxicity, side effects, interactions, and contraindications

Toxicity is rare in dietary intake but large amounts in supplement form may play havoc with your blood pressure and cause headaches, nausea and heartburn. Large amounts of this nutrient may also cause nerve damage. Toxicity symptoms include increased blood pressure and emotional agitation, insomnia, headaches, and tyrosine toxicity. Individuals with PKU and women who are lactating or pregnant should avoid supplementation. People with melanomas should also avoid Phenylalanine supplementation as it may stimulate the growth of this skin cancer. L-dopa competes with phenylalanine and should not be taken at the same time of day. 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.