PHENYLALANINE Overview Information
Phenylalanine is an amino acid, a “building block” of protein. There are three forms of phenylalanine: D-phenylalanine, L-phenylalanine, and the mix made in the laboratory called DL-phenylalanine. D-phenylalanine is not an essential amino acid, and its role in people is not currently understood. L-phenylalanine is an essential amino acid and is the only form of phenylalanine found in proteins. Major dietary sources of L-phenylalanine include meat, fish, eggs, cheese, and milk.
Phenylalanine is used for depression, attention deficit-hyperactivity disorder (ADHD), Parkinson's disease, chronic pain, osteoarthritis, rheumatoid arthritis, alcohol withdrawal symptoms, and a skin disease called vitiligo.
Some people apply it directly to the skin for vitiligo.
How does it work?
The body uses phenylalanine to make chemical messengers, but it is not clear how phenylalanine might work.
Possibly Effective for:
- A skin condition called vitiligo. Taking L-phenylalanine by mouth in combination with UVA exposure or applying L-phenylalanine to the skin in combination with UVA exposure seems to be effective for treating vitiligo in adults and in children.
Possibly Ineffective for:
- Attention deficit-hyperactivity disorder (ADHD). Some research suggests that patients with ADHD have lower levels of amino acids such as phenylalanine, so there was hope that providing phenylalanine might treat ADHD. However, taking phenylalanine by mouth does not seem to have any effect on ADHD symptoms.
- Pain. Taking D-phenylalanine by mouth does not need to reduce pain.
- Acupuncture anesthesia. Early research suggests that taking D-phenylalanine by mouth might enhance acupuncture anesthesia while having a tooth pulled. However, it does not seem to improve acupuncture anesthesia for back pain.
- Alcohol withdrawal. Early research suggests that taking a combination of D-phenylalanine, L-glutamine, and L-5-hydroxytryptophan for 40 days can improve some symptoms of alcohol withdrawal.
- Depression. Limited clinical research performed in the 1980s suggests L-phenylalanine or DL-phenylalanine might be useful for depression. However, this research needs to be confirmed. Taking D-phenylalanine does not appear to improve symptoms of depression.
- Multiple sclerosis. Early research suggests that using Cari Loder’s regiment, which includes L-phenylalanine, lofepramine, and intramuscular vitamin B12 for 24 weeks, does not improve disability in people with multiple sclerosis.
- Parkinson's disease. Limited research suggests taking one form of phenylalanine (D-phenylalanine) might decrease symptoms of Parkinson's disease. However, taking another form (DL-phenylalanine) does not seem to work.
- Phenylalanine deficiency. Early research suggests that taking phenylalanine by mouth might improve phenylalanine deficiency in children with tyrosinemia.
- Other conditions.
PHENYLALANINE Side Effects & Safety
L-phenylalanine is LIKELY SAFE for most people when consumed in amounts commonly found in foods.
Phenylalanine is POSSIBLY SAFE when taken by mouth as medicine.
There is not enough reliable information available about the safety of D-phenylalanine.
Special Precautions & Warnings:Pregnancy and breast-feeding: Phenylalanine is LIKELY SAFE when consumed in amounts commonly found in foods by pregnant women who have normal phenylalanine levels. However, having too much phenylalanine in the mother’s system during pregnancy can increase the chances of birth defects. The risk for facial defects is highest at weeks 10-14, nervous system and growth defects between 3-16 weeks, and heart defects at 3-8 weeks. For women who process phenylalanine normally and have normal levels, it is probably fine to get the amount of phenylalanine found in food, but not in higher doses. Do not take supplements. For women who have high levels of phenylalanine, even normal food amounts are UNSAFE. Additionally, experts recommend a low phenylalanine diet for at least 20 weeks before getting pregnant. This should reduce the risk of birth defects.
Phenylalanine is LIKELY SAFE for breast-feeding mothers whose bodies’ process phenylalanine normally to consume the amount of phenylalanine found in food. However, do not take more. Not enough is known about the safety of taking phenylalanine in medicinal amounts during breast-feeding.
Phenylketonuria (PKU) and other conditions that cause high levels of phenylalanine: Phenylalanine should be avoided in people with certain inherited disorders that cause their bodies to build up too much phenylalanine. Phenylketonuria (PKU) is one of these diseases. People with this disorder can develop mental retardation, high blood pressure, stroke, and many other serious health issues if they consume phenylalanine. PKU is so serious that babies are screened at birth to determine whether they have the disorder and will need a special diet to avoid these problems.
Schizophrenia: Use with caution. Phenylalanine can make a movement disorder (tardive dyskinesia) in people with schizophrenia worse.
Major Interaction Do not take this combination
- Levodopa interacts with PHENYLALANINE
Levodopa is used for Parkinson's disease. Taking phenylalanine along with levodopa can make Parkinson's disease worse. Do not take phenylalanine if you are taking levodopa.
Moderate Interaction Be cautious with this combination
- Medications for depression (MAOIs) interacts with PHENYLALANINE
Phenylalanine can increase a chemical in the body called tyramine. Large amounts of tyramine can cause high blood pressure. But the body naturally breaks down tyramine to get rid of it. This usually prevents the tyramine from causing high blood pressure. Some medications used for depression stop the body from breaking down tyramine. This can cause there to be too much tyramine and lead to dangerously high blood pressure.
Some of these medications used for depression include phenelzine (Nardil), tranylcypromine (Parnate), and others.
- Medications for mental conditions (Antipsychotic drugs) interacts with PHENYLALANINE
Some medications for mental conditions might cause jerky muscle movements. Taking phenylalanine along with some medications for mental conditions might increase the risk of jerky muscle movements.
Some medications for mental conditions include chlorpromazine (Thorazine), clozapine (Clozaril), fluphenazine (Prolixin), haloperidol (Haldol), olanzapine (Zyprexa), perphenazine (Trilafon), prochlorperazine (Compazine), quetiapine (Seroquel), risperidone (Risperdal), thioridazine (Mellaril), thiothixene (Navane), and others.
The following doses have been studied in scientific research:
- For a skin disease that produces white unpigmented patches (vitiligo): in adults, 50-100 mg/kg of L-phenylalanine is typically used per day along with exposure to sunlight.