What is Phenylalanine

Chemical Name: (S)-2-amino-3-phenylpropanoic acid

Molecular Weight: 165.2

Structrual Formula:

Nitrogen Content: 8.48%

Phenylalanine (13, 14)

  • L-phenylalanine is an essential amino acid which can be converted to L-tyrosine by a complex biochemical process which takes place in the liver
  • L-Phenylalanine is a neutral, genetically coded amino acid
  • one of the aromatic amino acids that exhibit ultraviolet radiation absorption properties
  • It is the most commonly found aromatic amino acid
  • Phenylalanine is available in three different forms – L-, D- and DL-. It has a phenyl side chain
  • L-Phenylalanine (LPA) is an electrically neutral amino acid found in proteins, coded for by DNA
  • Its mirror image, D-phenylalanine (DPA), can be synthesized artificially
  • The L- form is the most common and the type in which it is incorporated into the body’s proteins
  • Tyrosine is converted into L-DOPA, norepinephrine, and epinephrine
  • D-phenylalanine can only be converted into phenylethylamine
  • The D- form acts as a painkiller
  • The DL- a combination of the two. The synthesized mix DL-Phenylalanine (DLPA), which is a combination of the D- and L- forms, is used as a nutritional supplement

Phenylalanine and appetite control (263,38, 39, 40, 41)

  • L-Phenylalanine’s ability to suppress appetite by stimulating the production of the appetite-suppressing hormone, cholecystokinin, was proven in a laboratory study with rhesus monkeys
  • In the first test, the monkeys were given cholecystokinin intravenously, after having been deprived of food overnight. Sure enough, the monkey’s appetites were suppressed
  • In the second test, the monkeys again weren’t allowed to eat anything during the night previous to testing
  • Even though they were hungry, after they were given phenylalanine, the monkeys’ appetite was suppressed
  • The test indicates that phenylalanine helps release cholecystokinin, the hormone that suppresses appetite

Phenylalanine and Parkinson’s disease (261, 184)

  • A few isolated studies indicate that phenylalanine may be used against multiple sclerosis (6, 204) or Parkinson’s disease
  • Researchers found that the amino acid significantly reduced the severity of Parkinson’s symptoms like depression, speech impediments, limb rigidity, and walking difficult. The hand tremors, however, continued
  • The participants in this study took 1,250 mg of the amino acid twice a day for just four weeks

Phenylalanine and muscle protein recovery (194)

Phenylalanine and pain (258)

  • Research backs the use of phenylalanine to alleviate arthritis aches, back pain, and menstrual cramps, especially in the DL-form
  • It slows the body’s breakdown of endorphins and other natural painkillers, so their effects will last longer (205,206)
  • Phenylalanine and reduce inflammation / analgesic (205, 206)

Phenylalanine and depression (256, 265)

  • In a dose of 500-3,000 mg, phenylalanine, along with vitamin B6, produced an almost immediate improvement in thirty-one out of forty depressed patients
  • In addition to phenylalanine’s role in making adrenaline mimickers, it provides spirit-boosting endorphins
  • Phenylalanine is the only substance that the body can use to make phenylethlamine (PEA)
  • Low PEA level’s in depressed subjects show that phenylalanine is not being metabolized
  • Bipolar Depression (186, 187)

Phenylalanine and Premenstrual Tension (43)

Dosage Ranges and Duration of Administration

The following are the recommended dietary allowances for phenylalanine plus tyrosine, according to the National Research Council:

  • Birth to 4 months: 125 mg/kg/day
  • 5 months to 2 years: 69 mg/kg/day
  • 3 to 12 years: 22 mg/kg/day
  • Adults and teenagers: 14 mg/kg/day

Phenylalanine and Food

  • Phenylalanine can be found in dairy product, almonds, avocados, lima beans, peanuts and seeds

Dietary deficiency of Phenylalanine (61)

  • Symptoms of phenylalanine deficiency may include confusion, emotional agitation, depression, decreased alertness, decreased memory, behavioral changes, decreased sexual interest, bloodshot eyes, and cataracts

Toxicity and symptoms of high intake (61)

  • 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
  • Some people cannot metabolize phenylalanine and should not take supplementation of this amino acid

Precaution (205)

  • Anxiety, headaches, and hypertension are possible side effects of supplementation
  • Women who are lactating or pregnant should avoid supplementation
  • L-dopa competes with phenylalanine and should not be taken at the same time of day


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