Phenylalanine is an essential amino acid–amino acids being the building blocks of proteins. This amino acid is essential because the body cannot produce it using other amino acids, meaning it must come from one’s diet. Phenylalanine can be converted into tyrosine, another amino acid.

Health considerations

If an insufficient amount of essential amino acids are consumed consistently, those doing so may run the risk of being diagnosed with protein deficiencies such as kwashiorkor or marasmus. These deficiencies are often noted with symptoms such as bloated abdomen and fatigue, much the same as the symptoms of general malnourishment. Phenylketonuria is a congenital disorder in which the person cannot metabolize phenylalanine; the amino acid accumulates, generating toxic products.

Keep in mind

Labels declare phenylalanine content on aspartame-sweetened foods for phenylketonurics, not because phenylalanine is hazardous to general health.

May be found in

Aspartame, soy, seaweed, whitefish, cheese, milk, molluscs, egg whites, seal, whale


Medline Plus
Self Nutrition Data
WIKI Books

Alternative Spellings and Names

Phe, F

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