Phenylalanine: Benefits, Side Effects, and Food Sources

Phenylalanine comes in three different forms.

• L-phenylalanine: Natural form of phenylalanine
  • Naturally found in some foods, such as cow's milk and sweet potatoes.
  • Serves as a building block for various proteins that are produced in the body.
  • Transformed into tyrosine in the body, which is then utilized to make L-dopa. L-dopa is subsequently transformed into dopamine, epinephrine, and norepinephrine. These neurotransmitters have been linked to mood regulation.
• D-phenylalanine: Lab-created form of phenylalanine that closely resembles the structure of L-phenylalanine.
• DL-phenylalanine: Combines L-phenylalanine and D-phenylalanine.

There are many health benefits of phenylalanine. Although L-phenylalanine is best known as a brain supplement, researchers have investigated it for other possible uses, although additional studies are needed to confirm the effectiveness:

1. Vitiligo: Vitiligo is a disease that attacks melanin-producing cells (melanocytes) in the skin. Since melanin is responsible for the pigment in skin, this disease results in pale, colorless spots on the skin. The exact cause of vitiligo is not well understood. However, phenylalanine is required to make melanin. Therefore, phenylalanine supplementation along with light therapy has been used to treat vitiligo with promising results.
2. Parkinson's disease: Supplementing with D-phenylalanine (DPA) may help relieve symptoms such as tremors in Parkinson's patients. DPA should not be taken with L-dopa, however, because it may interfere with the transport of L-dopa to the brain. Additional research is needed in order to establish whether this treatment is effective.
3. Osteoarthritis: DPA supplementation has been proven to help reduce chronic pain associated with osteoarthritis. DPA inhibits the enzyme that breaks down some of the body's natural painkillers, enkephalins, which are similar to endorphins. An increase in the number of enkephalins may explain the reported pain-relieving effect of DPA.
4. Rheumatoid arthritis: D-phenylalanine has been used to treat chronic pain, particularly rheumatoid arthritis, with varying degrees of success. The effect of either form of phenylalanine in the treatment of people with rheumatoid arthritis remains unproven.
5. Depression: In some studies, people with depression who were treated with L-phenylalanine had similar results to those who took an antidepressant. L-phenylalanine can be converted to phenylethylamine, a naturally occurring chemical in the brain that may improve mood. L-phenylalanine is combined with its synthetic counterpart, DPA, to form DLPA. In a preliminary trial, DLPA (or the D-or L-form alone) decreased depression in 31 of 40 patients.
6. Alcohol withdrawal: Using L-tyrosine, DLPA, L-glutamine, prescription L-tryptophan, has been linked to fewer alcohol withdrawal symptoms.

The FDA considers L-phenylalanine to be generally safe. However, higher doses may cause side effects such as:

• Anxiety
• Nausea
• Fatigue
• Heartburn
• Headache
• Constipation

Women who are pregnant or nursing should avoid taking L-phenylalanine. Patients with phenylketonuria (PKU) should also avoid taking L-phenylalanine supplements. PKU is a hereditary phenylalanine metabolism disease, and phenylalanine can be harmful to people suffering from the condition.

Food sources of phenylalanine include:

• Aspartame, a popular artificial sweetener used in diet sodas, chewing gum, and cough drops
• Animal meat, such as chicken, beef, and pork
• Fish and shellfish
• Eggs
• Cow’s milk
• Cheeses
• Peanuts and peanut butter
• Walnuts
• Almonds
• Beans
• Legumes
• Soybeans (edamame) and soy products, such as tofu
• Artichokes
• Cilantro
• Parsley
• Watercress
• Bananas
• Passion fruit

Eating a diet rich in these foods can help prevent phenylalanine deficiencies. A balanced diet with enough protein may provide adequate phenylalanine. Since excessive consumption of supplements can be harmful, talk to your doctor before taking phenylalanine supplements.