The PKU Diet

Individuals with Phenylketonuria (PKU) are unable to properly metabolise one of the amino acids in protein. As a consequence, they must follow a strict low protein diet, perform regular blood tests to monitor levels and take a dietary supplement to avoid severe and irreversible brain damage. This diet is highly restrictive, they are unable to eat many foods including meat, dairy, eggs, wheat, rice and other grains, nuts and soy. Even intake of some vegetables and fruits must be restricted. Most foods need to be weighed and calculated for protein content to ensure that the daily allowance is not exceeded.


Due to the spectrum of severity in PKU, individual daily protein intake can vary from 1 gram to 23 grams of protein. The diet is mainly made up of man-made low protein foods with a minimal amount of natural foods. To show you how severe the diet is, below are natural foods and the protein content of these. This shows how individuals with PKU will NOT be able to live on a diet of natural foods alone.


To put this in perspective:

  • 120g banana (average sized) is 2 grams of protein
  • 50g of boiled potato is 1 gram of protein
  • Vitasoy Rice milk is 0.3/100ml, that equals to 1 gram protein for 1 cup (250ml)
  • 30g of protein of hot chips is 1 gram of protein
  • 75g of avocado is 1 protein
  • 20g of green peas is 1 gram of protein
  • 50g of boiled white rice is 1 protein

Next time you are in the supermarket, turn over the items you are looking at and look at the ‘protein’ part of the nutritional label. As you will see, most items are high in protein and cannot be consumed by an individual living with PKU. This is the struggle that those with this Inborn Error of Metabolism face every day.


The low protein foods that they can have are imported and are expensive. These make up the majority of the diet and keep blood levels within range. Individuals with PKU cannot drink regular milk, eat regular cheese, pasta, bread, biscuits or rice.


Some examples of the costs involved for common low protein foods are:

  • $15.75 for a 400g tin of milk replacer
  • $15.75 for 100g of egg replacer
  • $9.95 for 500g low protein pasta
  • $19.50 for 900g low protein cheese
  • $9.95 for 500g of low protein rice
  • $10.00 for a 400g loaf of bread
  • $19.50 for 12 cookies

Delivery of these foods costs from $35 to $90 depending on distance and weight.

As well as the diet, an individual with PKU also needs to take supplements. There are a variety of supplements available which cater for different age groups. In Australia there are 3 pharmaceutical companies which supply these. The supplements are provided through Pharmaceutical Benefits Scheme (PBS) and are necessary for an individual with PKU to ensure they are receiving all the vitamins & minerals that the diet alone cannot provide. The diet remains the same regardless of the type of supplement an individual takes.


There are drugs available internationally which increase the phenylalanine intake for an individual but this does not change the need for the supplements or the diet. One particular treatment available, a drug known as Kuvan (BH4), that does reduce the level of dietary restriction, but application to have this listed on the PBS was denied. This drug is successfully used in the US and many other countries. This drug does not work for most people with classic PKU.


Individuals with PKU need to conduct regular blood tests and send them to the laboratory for testing. They also need to attend the metabolic clinic at a major teaching hospital to monitor and ensure levels are kept in range. If levels are not closely monitored, diet is not maintained and supplement is not taken then the consequences are severe. Regardless of age, individual who do not stick to their diet will suffer severe brain damage. Individuals will start to have symptoms ranging from depression, anxiety, poor concentration, intellectual disability, cognitive defects, liver failure, seizures, mental retardation and would end up institutionalised. Many untreated PKU individuals require constant nursing care.


Without the early detection of Newborn Screening, Phenylketonuria would not be identified in newborns. We are very thankful for this as current research has shown that if this is picked up from birth and diet and monitoring is commenced immediately than the child will grow normally and be able to become a viable part of working society.


To date, the PKU Association of NSW has raised in excess of $1,000,000 to research at the Childrens Hospital at Westmead to find a better treatment of PKU enabling a more liberal diet of foods. This research is led by Professor John Christodoulou.


This diet is for life. There is no cure.