Editing Aspartame (section)

===Phenylalanine===

High levels of the naturally occurring [[essential amino acid]] [[phenylalanine]] are a health hazard to those born with [[phenylketonuria]] (PKU), a rare inherited disease that prevents phenylalanine from being properly metabolized.<ref name="phenyl">{{cite web |title=Phenylalanine |url=https://pubchem.ncbi.nlm.nih.gov/compound/Phenylalanine |publisher=PubChem, National Library of Medicine, US National Institutes of Health |access-date=2 June 2023 |date=27 May 2023 |archive-date=22 April 2023 |archive-url=https://web.archive.org/web/20230422081636/https://pubchem.ncbi.nlm.nih.gov/compound/Phenylalanine |url-status=live }}</ref> Because aspartame contains phenylalanine, foods containing aspartame sold in the US must state: "Phenylketonurics: Contains Phenylalanine" on product labels.<ref name=cfr/>

In the UK, foods that contain aspartame are required by the [[Food Standards Agency]] to list the substance as an ingredient, with the warning "Contains a source of phenylalanine". Manufacturers are also required to print "with sweetener(s)" on the label close to the main product name on foods that contain "sweeteners such as aspartame" or "with sugar and sweetener(s)" on "foods that contain both sugar and sweetener".<ref name="FSA2015">{{cite web |url=https://www.food.gov.uk/science/additives/aspartame |title=Aspartame |author=<!--Not stated--> |date=19 March 2015 |website=UK Food Standards Agency |access-date=28 June 2017 |url-status=live |archive-url=https://web.archive.org/web/20170711201731/https://www.food.gov.uk/science/additives/aspartame |archive-date=11 July 2017 }}</ref>

In Canada, foods that contain aspartame are required to list aspartame among the ingredients, include the amount of aspartame per serving, and state that the product contains phenylalanine.<ref name="hc2018">{{cite web |title=Mandatory Labelling of Sweeteners |url=http://www.inspection.gc.ca/food/requirements-and-guidance/labelling/industry/sweeteners/eng/1387749708758/1387750396304?chap=2 |publisher=Canadian Food Inspection Agency, Health Canada |access-date=23 August 2019 |date=11 May 2018 |archive-date=6 July 2023 |archive-url=https://web.archive.org/web/20230706042715/https://inspection.canada.ca/food-labels/labelling/industry/sweeteners/eng/1387749708758/1387750396304?chap=2 |url-status=live }}</ref>

Phenylalanine is one of the [[essential amino acid]]s and is required for normal growth and maintenance of life.<ref name=phenyl/> Concerns about the safety of phenylalanine from aspartame for those without phenylketonuria center largely on hypothetical changes in [[neurotransmitter]] levels as well as ratios of neurotransmitters to each other in the blood and brain that could lead to neurological symptoms. Reviews of the literature have found no consistent findings to support such concerns,<ref name=EFSAExperts/><ref name=Butchko/> and, while high doses of aspartame consumption may have some biochemical effects, these effects are not seen in toxicity studies to suggest aspartame can adversely affect neuronal function.<ref name=phenyl/> As with methanol and aspartic acid, common foods in the typical diet, such as milk, meat, and fruits, will lead to ingestion of significantly higher amounts of phenylalanine than would be expected from aspartame consumption.<ref name=Butchko/>