Phenylalanine is an essential amino acid or protein building block that is not produced by the body but must come from dietary sources. It is found in a variety of foods that contain protein, such as meats, poultry, fish, eggs and milk, and is available as a dietary supplement. It is generally converted into tyrosine, another amino acid essential to protein synthesis and other bodily functions. Phenylalanine supplements may cause side effects, so it is important to speak with a doctor before taking phenylalanine.
Side Effects
DL-phenylalanine supplements, a combination of natural and synthetic phenylalanine, may cause unwanted side effects, especially in high doses, according to the University of Maryland Medical Center. Children may experience anxiety and hyperactivity. High doses of phenylalanine supplements can also cause nausea, heartburn and headaches, and doses above 5,000 mg per day can be toxic, leading to nerve damage.
Drug Interactions
Certain medications may interact with phenylalanine supplements and should be used with caution under doctor supervision or not at all. Phenylalanine can cause a dangerous rise in blood pressure in individuals taking a class of antidepressant medications known as MAOIs, or monoamine oxidase inhibitors, according to the University of Maryland Medical Center. Phenylalanine supplements can worsen tardive dyskinesia for those on certain antipsychotic medications. Tardive dyskinesia is a side effect of neuroleptic drugs, causing uncontrolled jerky movements of the face, arms, legs and hands. Phenylalanine also decreases the absorption and thus effectiveness of levodopa and baclofen, medications used in the treatment of Parkinson's disease and muscle spasms, respectively.
Phenylketonuria
Phenylketonuria is a rare, genetic disease in which the body is unable to break down phenylalanine. Individuals diagnosed with phenylketonuria are missing the enzyme phenylalanine hydroxylase, which converts phenylalanine into tyrosine. Eating foods or taking supplements with phenylalanine can lead to a dangerous buildup in the body. This can lead to mental retardation, behavioral issues, seizures, hyperactivity, growth issues and changes to the skin and hair, according to the Mayo Clinic. Avoiding phenylalanine supplements and in the diet can prevent side effects and complications.
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