Sweet'N Low sweetener packet

Inherited metabolic diseases

Defects in enzymes can lead to disease

Phenylketonuria diagram

‘Big Picture: Number Crunching’ (2013)

Children born with phenylketonuria (PKU) must have very little protein in their diet and avoid drinks containing the sweetener aspartame, which is made from phenylalanine and another amino acid. Such drinks have to carry a warning that they contain phenylalanine.

Following this restricted diet, affected babies suffer no harm. Since the 1960s, all babies in the UK have been tested for PKU within a week of birth with the Guthrie test, which uses a drop of blood from a heel prick. About nine babies in every 100,000 have PKU, and the test costs £1 a time. As well as avoiding disability, mass testing is cheaper than the cost of caring for children with PKU who are untreated.

Lead image:

Melissa Cuppett/Flickr CC BY NC


Further reading

About this resource

This resource was first published in ‘Food and Diet’ in June 2011 and reviewed and updated in August 2016.

Microbiology, Medicine, Health, infection and disease
Food and Diet
Education levels:
16–19, Continuing professional development