When you buy a diet coke, or any other consumables
containing the artificial sweetener aspartame, you’ll see a warning against
consuming the product if you have phenylketonuria, an inherited metabolic
disorder.
“Artificial” sweeteners, such as NutraSweet and Equal, are
not saccharides – the simple carbohydrates we call sugars. Instead, the
sweetener aspartame is a methyl ester comprising two joined amino acids:
aspartic acid and phenylalanine (Phe) – this is important for later, so keep it
in mind.