Editing Phenylalanine (section)

==Phenylketonuria==
{{main|Phenylketonuria}}
The genetic disorder [[phenylketonuria]] (PKU) is the inability to metabolize phenylalanine because of a lack of the enzyme [[phenylalanine hydroxylase]]. Individuals with this disorder are known as "phenylketonurics" and must regulate their intake of phenylalanine. Phenylketonurics often use blood tests to monitor the amount of phenylalanine in their blood.  Lab results may report phenylalanine levels using either mg/dL and μmol/L. One mg/dL of phenylalanine is approximately equivalent to 60 μmol/L.

A (rare) "variant form" of phenylketonuria called [[hyperphenylalaninemia]] is caused by the inability to synthesize a [[Cofactor (biochemistry)|cofactor]] called [[tetrahydrobiopterin]], which can be supplemented. Pregnant women with hyperphenylalaninemia may show similar symptoms of the disorder (high levels of phenylalanine in blood), but these indicators will usually disappear at the end of gestation.  Pregnant women with PKU must control their blood phenylalanine levels even if the fetus is heterozygous for the defective gene because the fetus could be adversely affected due to hepatic immaturity.{{medcn|date=April 2016}}

A non-food source of phenylalanine is the artificial sweetener [[aspartame]]. This compound is metabolized by the body into several chemical byproducts including phenylalanine. The breakdown problems phenylketonurics have with the buildup of phenylalanine in the body also occurs with the ingestion of aspartame, although to a lesser degree. Accordingly, all products in Australia, the U.S. and Canada that contain aspartame must be labeled: "Phenylketonurics: Contains phenylalanine." In the UK, foods containing aspartame must carry ingredient panels that refer to the presence of "aspartame or E951"<ref>{{cite web | url = http://www.food.gov.uk/safereating/chemsafe/additivesbranch/sweeteners/55174#h_4 | title = Aspartame | publisher = Food Standards Agency | location = UK | access-date = 2007-06-19 | archive-date = 2012-02-21 | archive-url = https://web.archive.org/web/20120221223646/http://www.food.gov.uk/safereating/chemsafe/additivesbranch/sweeteners/55174#h_4 | url-status = dead }}</ref> and they must be labeled with a warning "Contains a source of phenylalanine." In Brazil, the label "Contém Fenilalanina" (Portuguese for "Contains Phenylalanine") is also mandatory in products which contain it. These warnings are placed to help individuals avoid such foods.