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Phenylalanine comes in several forms as a supplement:

  • L-phenylalanine is an essential amino acid. It's also found in protein in the foods we eat.
  • D-phenylalanine
  • DL-phenylalanine, which contains both the D- and L-forms

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Why do people take phenylalanine?

Phenylalanine is not a widely accepted treatment for any condition. But people have tried to treat a number of conditions with phenylalanine, including:

Some research, mainly from the 1970s and 1980s, offers some support for using it for depression. Several studies also showed that L-phenylalanine plus ultraviolet A light may be helpful for people with vitiligo.

There is less evidence to support its use for other conditions.

Optimal doses of phenylalanine have not been set for any condition. Quality and active ingredients in supplements may vary widely from maker to maker. This makes it difficult to set a standard dose. However, commonly used dosages, depending on the condition, range from 150 mg to 5,000 mg daily.

Can you get phenylalanine naturally from foods?

Phenylalanine is found in many foods, including:

  • Meat
  • Eggs
  • Fish
  • Cheese
  • Products containing aspartame

What are the risks of taking phenylalanine?

Phenylalanine can trigger allergic reactions, with symptoms such as:

Side effects may include:

Doses higher than 5,000 milligrams a day can cause nerve damage.

Risks. People with certain conditions should avoid using this supplement, including:

You also should avoid the supplement if you have sensitivity to phenylalanine or a condition in which your body can't break down phenylalanine.

And use caution in taking phenylalanine if you have:

Also, it is unknown whether this supplement is safe in women who are pregnant or breastfeeding.

Interactions. Phenylalanine can cause tardive dyskinesia in people taking antipsychotic medicines.

If taken with certain antidepressants, this supplement could lead to:

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