Mental Health Home > Dangers of Phenylalanine

Many people are concerned that phenylalanine may not be safe. This may be due to warnings they see on the labels of products containing aspartame or certain Web sites. However, phenylalanine is a naturally occurring amino acid necessary for the building of proteins. The only dangers phenylalanine poses are to people with phenylketonuria, a rare genetic condition.

Dangers of Phenylalanine: An Overview

Many people believe that phenylalanine is a toxic, dangerous chemical that should be avoided at all costs. But is it really dangerous? If not, why is there so much concern about the safety of phenylalanine? This article will attempt to answer these questions.

Is Phenylalanine Dangerous? -- Understanding the Facts

First, a little scientific background is necessary. The following are basic facts known about phenylalanine:
  • Phenylalanine is an essential amino acid. This means that it is necessary for human nutrition and must be obtained through dietary sources, since the body cannot make its own phenylalanine.
  • Phenylalanine is important for building proteins. It is also used by the body to make tyrosine, another important amino acid.
  • Phenylalanine is found in many natural foods, such as meat, fish, eggs, cheese, and milk. It is not an "unnatural" substance.

The Warnings

Pick up almost any can of diet soda (or any other "diet" food sweetened with aspartame) and you will notice a warning that the product contains phenylalanine. This often causes people worry and fear. After all, phenylalanine must be dangerous; otherwise, why would a warning be necessary? The answer is simple.
There is a rare genetic condition known as phenylketonuria (PKU). People with this condition are born with no (or a very low) ability to process phenylalanine in the body. In these people, phenylalanine can build up to abnormally high levels (much higher than could be obtained in people without PKU). These extremely high levels of phenylalanine can cause serious problems. People with PKU must limit their dietary intake of phenylalanine, which is the purpose of the warning on products that contain aspartame, since phenylalanine is a component of aspartame. This warning only applies to people with PKU; it has no importance for everyone else.
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
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