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Home > Vitafriendspku > Your pku journey > Information for Caregivers (Children)

Information for Caregivers (Children)

What is PKU?

PKU stands for Phenylketonuria. PKU is an inherited condition – a disorder of protein metabolism.

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Protein is made up of small units or building blocks called amino acids. There are about 20 different amino acids, and some of these must be provided by the diet as the body cannot make them. For this reason, they are called “essential” amino acids. One of these essential amino acids is called phenylalanine (phe).

If someone has PKU then phe cannot be converted properly by the body. Therefore, it builds up in the blood to levels that are harmful to the brain. 

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How is PKU managed?

PKU is managed by a low protein diet, supplemented with protein substitutes to meet their nutritional needs. A child with PKU will be seen by a dietitian on a regular basis to help manage their condition.

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What is a low protein diet?

Individuals with PKU must avoid high protein foods. These include:

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  • Meat, red and white including beef, lamb, chicken and pork  
  • Fish and other seafood  
  • Quorn and other vegetarian meat alternatives  
  • Eggs  
  • Cheese  
  • Nuts & Seeds  
  • Dairy products including milk, yoghurt  


Foods like bread, pasta and cakes also contain small but significant amounts of protein. Specially manufactured low protein versions of these foods are often prescribed and parents will provide you with a supply of these.

Some protein (naturally occurring in particular foods) needs to be provided and may come from foods such as potatoes, breakfast cereal or rice and certain vegetables such as sweetcorn, peas and spinach. Parents, with the help of their dietitians, will make sure you are completely familiar with what is permitted in the diet.

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What happens if a child with PKU accidentally eats a food containing high of amounts protein?

Accidents can and will happen and there will be no immediate reaction if a child eats a food not permitted in their diet. This is different to the instant reaction that a child with a nut allergy may have. There is no need to seek medical attention.

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However, it is very important to make sure that mistakes do not happen often and it is always important to let a child’s parents know if they have eaten something in error, as they will need to let their dietitian know.

People with PKU still need protein to support their growth and development and the protein provided from foods (called natural protein and counted as grams of protein) is not sufficient to provide your child’s requirements, hence extra protein that is phe-free is required.

A protein substitute provides all other parts of protein, without the phe and usually contains vitamins and minerals too. It is often taken 3 times per day and should be treated as though it is medicine as it is a very important component of the PKU diet.

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Can I mix the protein substitute with food or drinks?

No. Protein substitutes must not be mixed into foods or drinks.

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This is because if the child does not finish their meal or drink it is impossible to know how much of the protein substitute that they did not manage

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What happens if a child with PKU won’t take their protein substitute?

The protein substitute needs to be treated like a medicine and taken in the full amount each day.

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There may be times a child does not want to take their protein substitute or feel unwell, but missing a day is not an option as this may become a habit and break their routine. Make sure you inform the parents immediately if their child is refusing to take their protein substitute.

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Learn more about PKU

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