Phenylalanine

Phenylalanine is an essential amino acid (a building block for proteins in the body), meaning the body needs it for health but cannot make it. You have to get it from food. Phenylalanine is found in 3 forms.

The body changes phenylalanine into tyrosine, another amino acid that is needed to make proteins and brain chemicals, including L-dopa, epinephrine, norepinephrine, and thyroid hormones. Because norepinephrine affects mood, different forms of phenylalanine have been proposed to treat depression. Symptoms of phenylalanine deficiency include:

On the other hand, a rare metabolic disorder called phenylketonuria (PKU) occurs in people who are missing an enzyme that the body needs to use phenylalanine. That causes high levels of phenylalanine to build up. If it is not treated before 3 weeks of age, PKU can cause severe, irreversible intellectual disability. In the United States, newborns are tested for PKU during the first 48 to 72 hours of life. Older, untreated children become hyperactive with autistic behaviors, including purposeless hand movements and rhythmic rocking.

People with PKU must eat a diet that avoids phenylalanine and take tyrosine supplements for optimal brain development and growth. Compliance with treatment in people with PKU has a greater impact on cognition during the first 12 years of life compared to the influence beyond 12 years.

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Review Date: 8/6/2015  

Reviewed By: Steven D. Ehrlich, NMD, Solutions Acupuncture, a private practice specializing in complementary and alternative medicine, Phoenix, AZ. Review provided by VeriMed Healthcare Network.

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