Phenylalanine, a non-nutrient amino acid, is found in two forms: L-phenylalanine , a natural amino acid found in proteins, and D-phenylalanine, a form synthesized in a laboratory. In the body, phenylalanine is converted into another amino acid, tyrosine, which in turn is converted into L-dopa, norepinephrine, and epinephrine, three key neurotransmitters in the brain. D-phenylalanine has been proposed to treat Parkinson's disease, but so far, the studies have not shown good evidence that it works. Phenylalanine supplements should always be taken only under the supervision of a knowledgeable doctor.
Parkinson's Disease
Parkinson's disease is a chronic disorder typically caused by the death of dopamine-producing nerve cells in certain parts of the brain, leading to characteristic problem with movements. L-dopa is an important precursor in the process of producing dopamine in the brain of patients with Parkinson's disease. L-dopa also contains phenylalanine as part of its structure and is therefore necessary to produce L-dopa in people with Parkinson's disease.
Research
According to University of Maryland Medical Center, one animal study suggests that D-phenylalanine may be used as a treatment for Parkinson's disease. D-phenylalanine may improve walking disabilities, rigidity, speech difficulties and depression associated with Parkinson's disease. The study does not prove whether phenylalanine would have the same effect on humans.
Interactions
A study published in 1984 in "The New England Journal of Medicine" suggests that phenylalanine may interfere with the absorption or action of levodopa, a drug used to treat Parkinson's disease. Researchers found that high-protein meal or oral phenylalanine at a dosage of 100 mg per kg body weight may reverse the therapeutic effect of infused levodopa in patients with Parkinson's disease.
Safety Issues
As with any medication, side effects may also occur with phenylalanine. Doses higher than 5,000 mg a day may be toxic to the brain and may cause mild side effects such as nausea, heartburn and headaches, according to the University of Maryland Medical Center. The maximum safe dosages of phenylalanine have not been established for pregnant women and young children. Because of the potential for side effect, supplement should be taken under the supervision of a doctor.
References
- NYU Langone Medical Center: Phenylalanine
- National Institute of Neurological Disorder and Stroke: Parkinson's Disease
- University of Maryland Medical Center: Phenylalanine
- "The New England Journal of Medicine"; The "On"- "Off" Phenomenon in Parkinson's Disease. Relation to Levodopa Absorption and Transport; J. Nutt et al.; Feb 1984.
