PKU FAQs

PKU (Phenylketonuria) Frequently Asked Questions

PKU, or phenylketonuria, is a disorder where a faulty gene causes a deficiency in a liver enzyme called phenylalanine hydroxylase (PAH). The body needs PAH to break down an amino acid called phenylalanine (Phe), which is present in foods containing protein. When a person with PKU eats food high in protein, their bodies can’t break down the Phe in the usual way, and it accumulates in the blood and brain, where it can cause problems. With early detection and commencement of treatment, people with PKU can live life to their full potential.

Reference source:

The Australian Society for Inborn Errors of Metabolism (ASIEM). The PKU Handbook. Available at: https://www.hgsa.org.au/resources/asiem-resources-for-parents-and-families/asiem-dietary-handbooks. Accessed January 2021.

Yes, PKU is an inherited genetic disorder. It occurs when someone has mutations in both copies of the phenylalanine hydroxylase (PAH) gene, which makes PAH, an enzyme needed to break down the amino acid phenylalanine (Phe).

Our genes come in pairs, with one copy inherited from each parent. A person with one faulty copy of the PAH gene is called a ‘carrier’ of PKU. A carrier is not affected by PKU, but they can pass the faulty PAH gene to their children.

A person with PKU has inherited a faulty copy of the PAH gene from each parent.

It is important to note that everyone has some faults in their genes. PKU is not something that is caused by anything a parent has done, and it’s not something that could have been avoided. It’s a condition that occurs by chance when two people with the same rare genetic fault have a child together.

Reference source:

The Australian Society for Inborn Errors of Metabolism (ASIEM). The PKU Handbook. Available at: https://www.hgsa.org.au/resources/asiem-resources-for-parents-and-families/asiem-dietary-handbooks. Accessed January 2021.

Treatment throughout infancy and childhood is essential to prevent high phenylalanine (Phe) levels causing damage to the developing brain.

Without early treatment, babies show signs of slow development by the age of one year. When PKU remains untreated throughout childhood, it leads to severe problems, which can include irreversible intellectual disability, microcephaly (small head size), problems with movement and coordination, eczema and skin rashes, autism, seizures, developmental problems, and abnormal behavioural and psychiatric symptoms.

Reference source:

The Australian Society for Inborn Errors of Metabolism (ASIEM). The PKU Handbook. Available at: https://www.hgsa.org.au/resources/asiem-resources-for-parents-and-families/asiem-dietary-handbooks. Accessed January 2021.

People with PKU follow a low protein diet and take a nutritional supplement to treat their condition.

Generally, PKU foods to avoid include those which are high in protein, like dairy products, red meat, chicken, fish, eggs, nuts, tofu and legumes. They also need to avoid some types of artificial sweeteners that are high in phenylalanine (Phe). People with PKU may also eat special, low protein versions of common foods like bread, rice, pasta and flour. Click here to shop our inspiring range of low protein foods. The PKU diet is rich in fruits and vegetables, and can be varied, tasty and satisfying. Click here to see our collection of delicious low protein recipes.

The nutritional supplement makes up for the nutrients that someone with PKU doesn’t get in their diet. It contains all the essential amino acids except for Phe, along with vitamins and minerals. Supplements come in many forms and flavours, including powders, ready-to-drink liquids, tablets, and puddings, giving people with PKU the option to choose the type of supplement that they like the best. Click here to explore and purchase our wide range of PKU supplements.

Reference source:

The Australian Society for Inborn Errors of Metabolism (ASIEM). The PKU Handbook. Available at: https://www.hgsa.org.au/resources/asiem-resources-for-parents-and-families/asiem-dietary-handbooks. Accessed January 2021.

In Australia, people with PKU are managed with a low protein diet and a nutritional supplement. When started early, this is very successful, allowing people with PKU to grow and develop to their full potential. Research has shown that staying on diet for life has many health benefits, and this is what doctors in Australia recommend.

Some people with PKU may be prescribed a medicine by their doctor to help their phenylalanine hydroxylase (PAH) enzymes break down more phenylalanine (Phe). This isn’t a cure for PKU, and it doesn’t work for all people with PKU. Each person with PKU should have an individual treatment plan which they have worked out together with their metabolic team.

Regular blood tests to monitor Phe levels and attendance at metabolic clinic appointments are also an important part of PKU treatment.

Reference source:

The Australian Society for Inborn Errors of Metabolism (ASIEM). The PKU Handbook. Available at: https://www.hgsa.org.au/resources/asiem-resources-for-parents-and-families/asiem-dietary-handbooks. Accessed January 2021.

Around one in every 10,000 babies born in Australia and one in 22,000 babies born in New Zealand is diagnosed with PKU. If someone in the family has PKU, these odds are much higher. In families where one child has PKU, there is a one in four chance that each of their full siblings will also have PKU, and a 50% chance that a full sibling will be PKU carrier (which means they do not have PKU, but may pass PKU on to any children they may have if their partner has PKU, or is a carrier too).

Reference source:

The Australian Society for Inborn Errors of Metabolism (ASIEM). The PKU Handbook. Available at: https://www.hgsa.org.au/resources/asiem-resources-for-parents-and-families/asiem-dietary-handbooks. Accessed January 2021.

The newborn screening test for PKU detects high levels of phenylalanine (Phe) in the blood. In newborns with PKU this is caused by phenylalanine hydroxylase (PAH) deficiency, but there may be other causes for high blood Phe levels, including prematurity, high protein intake, problems with the liver or problems with another enzyme involved in breaking down Phe in the body. Sometimes there is no reason for high Phe levels and they will go down without treatment.

If the newborn screening test detects high Phe levels, more tests are done to work out the cause.

Reference source:

The Australian Society for Inborn Errors of Metabolism (ASIEM). The PKU Handbook. Available at: https://www.hgsa.org.au/resources/asiem-resources-for-parents-and-families/asiem-dietary-handbooks. Accessed January 2021.

van Wegberg AMJ et al. Orphanet J Rare Dis 2017;12:162. doi:10.1186/s13023-017-0685-2.

In Australia and New Zealand, all babies are tested for PKU (and other metabolic conditions), usually when they are two or three days old. A small blood sample is taken from a needle prick on the baby’s heel and the levels of Phe are measured. If the levels of phenylalanine (Phe) are high, more tests are done to work out whether the baby has PKU.

Reference source:

The Australian Society for Inborn Errors of Metabolism (ASIEM). The PKU Handbook. Available at: https://www.hgsa.org.au/resources/asiem-resources-for-parents-and-families/asiem-dietary-handbooks. Accessed January 2021.

PKU is a disorder that can be treated very successfully with a low protein diet. People with PKU who have been treated early and continuously may not experience any symptoms at all.

There is some association between non-compliance to PKU diet and problems with thinking and mood. Some adults and adolescents with PKU have reported symptoms including trouble understanding information, attention problems, problems with memory and communicating, as well as social and emotional difficulties. Some studies have shown that these problems occur more often when people with PKU have higher phenylalanine (Phe) levels. Many adults and adolescents who have relaxed their diet or gone off diet say that they feel better and think more clearly when they return to diet.

When PKU remains untreated throughout childhood, it leads to severe problems. See ‘What happens if PKU goes untreated?’ in this FAQ

Reference source:

The Australian Society for Inborn Errors of Metabolism (ASIEM). The PKU Handbook. Available at: https://www.hgsa.org.au/resources/asiem-resources-for-parents-and-families/asiem-dietary-handbooks. Accessed January 2021.

van Wegberg AMJ et al. Orphanet J Rare Dis 2017;12:162. doi:10.1186/s13023-017-0685-2.

Keeping phenylalanine (Phe) levels in the right range is a balancing act, and regular blood tests to check Phe levels are an important part of treatment for someone with PKU. Blood is taken from a small skin prick on the finger or heel, and sent to a laboratory for testing. Blood tests are usually more frequent during childhood, because rapid growth can cause Phe levels to fluctuate. A baby or a child may have several blood tests a week. As someone with PKU gets older, Phe levels tend to become a bit more predictable, so the metabolic clinic might decide that testing needs to be less frequent. If someone with PKU gets sick, they may need to have extra blood tests to figure out whether their Phe levels are too high or too low.

Reference source:

The Australian Society for Inborn Errors of Metabolism (ASIEM). The PKU Handbook. Available at: https://www.hgsa.org.au/resources/asiem-resources-for-parents-and-families/asiem-dietary-handbooks. Accessed January 2021.

National PKU Alliance (NPKUA). PKU Handbook. A Guide for PKU from Diagnosis to Adulthood. Available at: https://www.npkua.org/portals/0/pdfs/pkubinder/PKU%20Binder%202011.pdf. Accessed February 2021.

If the results of the newborn screening test show that phenylalanine (Phe) levels in the blood are high (see ‘When is PKU testing done?’), more tests will be done to work out whether this is because of PKU, or another cause.

This might include further blood tests to look at the levels of Phe and enzymes in the blood, or urine tests, which can tell the doctors more about the way the body is metabolising Phe. In some cases, genetic testing can be done to learn more about the type of disorder someone has.

Reference source:

The Australian Society for Inborn Errors of Metabolism (ASIEM). The PKU Handbook. Available at: https://www.hgsa.org.au/resources/asiem-resources-for-parents-and-families/asiem-dietary-handbooks. Accessed January 2021.

van Wegberg AMJ et al. Orphanet J Rare Dis 2017;12:162. doi:10.1186/s13023-017-0685-2.

There’s nothing you can do to prevent PKU.

PKU comes about when two people with the same rare genetic fault have a child together. Everyone has a number of faults in their genetic make-up. PKU is not something that can be avoided, and it’s not due to anything a parent has done.

If a family has one child with PKU, pre-natal testing may be possible in further pregnancies to see whether the foetus is affected. However, this is rarely requested, because people with PKU can be treated successfully, and live normal, healthy lives.

Reference source:

The Australian Society for Inborn Errors of Metabolism (ASIEM). The PKU Handbook. Available at: https://www.hgsa.org.au/resources/asiem-resources-for-parents-and-families/asiem-dietary-handbooks. Accessed January 2021.

PKU can affect anyone, but the prevalence varies worldwide. In Australia about one in 10,000 people have PKU, and in New Zealand, the figure is about one in 22,000. Across Europe, the figure is approximately one in 10,000 people, with higher rates in some countries, such as Ireland and Turkey, and a very low rate in Finland.

Males and females have an equal chance of inheriting PKU.

Reference source:

The Australian Society for Inborn Errors of Metabolism (ASIEM). The PKU Handbook. Available at: https://www.hgsa.org.au/resources/asiem-resources-for-parents-and-families/asiem-dietary-handbooks. Accessed January 2021.

van Wegberg AMJ et al. Orphanet J Rare Dis 2017;12:162. doi:10.1186/s13023-017-0685-2.

If a family has one child with PKU, pre-natal testing may be possible in further pregnancies to see whether the foetus is affected. However, this is rarely requested, because people with PKU can be treated successfully, and live normal, healthy lives.

Reference source:

The Australian Society for Inborn Errors of Metabolism (ASIEM). The PKU Handbook. Available at: https://www.hgsa.org.au/resources/asiem-resources-for-parents-and-families/asiem-dietary-handbooks. Accessed January 2021.

There is no cure for PKU, but it is a condition that can be managed successfully through a low protein diet that includes a nutritional supplement, ongoing monitoring of phenylalanine (Phe) levels to ensure these are in the desired range, and regular attendance at the metabolic clinic.

Treatment with a prescription medication may help some people control their Phe levels. This medication is not a cure, and these people may still need to restrict their protein intake and take a nutritional supplement. Medication does not work for everyone with PKU – only some people are responsive to this treatment.

Reference source:

The Australian Society for Inborn Errors of Metabolism (ASIEM). The PKU Handbook. Available at: https://www.hgsa.org.au/resources/asiem-resources-for-parents-and-families/asiem-dietary-handbooks. Accessed January 2021.

PKU was first identified in 1934, when phenylketone bodies, a by-product of abnormal phenylalanine (Phe) breakdown, were detected in the urine of people displaying the symptoms of untreated PKU.

It was first reported that PKU could be effectively treated with a low Phe diet in 1953.

Reference source:

The Australian Society for Inborn Errors of Metabolism (ASIEM). The PKU Handbook. Available at: https://www.hgsa.org.au/resources/asiem-resources-for-parents-and-families/asiem-dietary-handbooks. Accessed January 2021.

van Wegberg AMJ et al. Orphanet J Rare Dis 2017;12:162. doi:10.1186/s13023-017-0685-2.

PKU is a genetic condition that people are born with. Because all newborns are screened for PKU in Australia and New Zealand, PKU is usually detected in very early infancy.

On very rare occasions, people who were born with mutations in both their phenylalanine hydroxylase (PAH) genes do not develop any symptoms of PKU (which can resemble other common neurological disorders) until later in life.

Reference source:

The Australian Society for Inborn Errors of Metabolism (ASIEM). The PKU Handbook. Available at: https://www.hgsa.org.au/resources/asiem-resources-for-parents-and-families/asiem-dietary-handbooks. Accessed January 2021.

van Wegberg AMJ et al. Orphanet J Rare Dis 2017;12:162. doi:10.1186/s13023-017-0685-2.

Tufekcioglu Z et al. Neurocase 2016;22(3):273–75.

Wang C, Li J. Medicine (Baltimore) 2018;97(8):e9801. doi:10.1097/MD.0000000000009801.

It’s easy to feed your possible with Nutricia. You can place your low protein food (Loprofin) order through the online Nutricia Store and have it delivered to your door. Protein substitute formulas, including baby formula, toddler milk replacement drinks, and oral nutritional supplements are available through Nutricia Home Pharmacy, for people with PKU and other medical conditions requiring dietary management.

There sure is! If you sign up to our Partner for Life program, you’ll enjoy benefits including free home delivery of Nutricia low protein products, support, tools and services to help you stay on track, as well as reminders to make sure you always have a steady supply of PKU supplements and low protein food so you can feed your possible. It’s free to join, and we’d love to have you as a member.

Yes! You can inspire others in the low protein community by sharing your favourite low protein recipes at our Recipe Hub. On each page, you will see a ‘Submit Your Recipe’ button. Before you start, you’ll need to register and provide some basic information, but once you’re in, you can start showing others how you feed your possible. You’ll also be able to rate recipes on the Recipe Hub, and save your favourites so you can access them at the click of a button. What are you waiting for?

People with PKU who live in Australia can set up a regular order for PKU supplements via Nutricia Home Pharmacy. Simply phone our pharmacy team on 1800 884 367 and select option 2.

Unfortunately, we cannot offer this service to New Zealand residents, nor do we currently offer an online ordering service. We’re always looking for ways to improve the online experience for our valued customers and we hope to add this functionality soon. If you have any other suggestions or ideas, we’d love to hear from you.

There are many ways you can feed your possible at Low Protein Connect. Get inspired by our low protein recipes, discover flavour and variety in the online store where you’ll find a wide range of PKU supplements and low protein foods, and take time out for your wellbeing with our low protein lifestyle tips.

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