You may have seen product labels warning of the presence of the amino acid phenylalanine. These alerts are for individuals who have phenylketonuria, or PKU, a condition that prevents the body from properly metabolizing phenylalanine. People with PKU take the amino acid tyrosine as a substitute for phenylalanine. You do not need to substitute phenylalanine unless you have PKU, so talk to your doctor before making substitutions.
Phenylalanine
Phenylalanine is an amino acid, which is a subunit that makes up protein. Protein foods contain various amounts of about 20 primary amino acids. Each amino acid serves a unique function. Phenylalanine is needed for your body to make tyrosine, another amino acid. Tyrosine plays an important role in your health. It is needed for your body to produce certain brain chemicals known as neurotransmitters. It is also needed to make thyroid hormones.
PKU
PKU is a rare genetic abnormality present at birth. Babies are screened for it when born; if the condition is detected, they will need to be fed a strict phenylalanine-free diet. Since phenylalanine is crucial to your body as the "parent" nutrient needed to make tyrosine, people born with PKU must substitute with tyrosine instead. Left untreated, attention deficit disorder manifests as the most common problem, according to PubMed health. Other issues include skin rashes, jerking movements in arms and legs and seizures.
Sources
Phenylalanine is generally found in protein-containing foods, but it is also found in diet food and beverages that use the sweetener aspartame. The richest phenylalanine sources include beef, chicken, fish, milk and milk products such as yogurt and cheese. Eggs are also phenylalanine-rich. You must avoid these foods if you and your child have PKU.
Substitution
Because many of the same foods that contain phenylalanine also contain tyrosine. a dietary supplement is used as a substitute. It is important to talk to your health care provider before taking tyrosine supplements. The typical adult dose is 500 to 1,000 milligrams taken three per day. This is generally taken about 30 minutes prior to each main meal. The dose for children varies. Your doctor can assess your child to determine how much is needed. Tyrosine can cause dangerously high blood pressure when taken with antidepressant medications. Tell your doctor if you are currently taking medication.
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