Weaning your baby with PKU

During your baby’s first few months they will get all the nutrition they need from breast milk and/or infant formula and their protein substitute (Phe-free infant formula). From around 6 months they will move onto the next stage of feeding, known as weaning, where solids foods are introduced.

Your dietitian will be there to guide you through this transition, step by step. Try to enjoy the process, and give your little one a positive feeding experience which will set them up for the road ahead.

Getting started

Babies with PKU should start to wean at the same age as any other baby. This is usually around 6 months of age, and no earlier than 17 weeks. Speak to your dietitian about choosing the right time.

Once you and your baby are ready to begin weaning, the first solids your dietitian will recommend are foods very low in Phe / protein. The Phe / protein in the diet will continue to be provided by breastmilk or infant formula; meaning that you and your baby will be able to learn to feed and make a mess without worrying about how much ends up on little faces and the floor! The volume of protein substitute should remain the same during this initial period, unless advised otherwise by your healthcare professional.

Your dietitian will give you a list of low Phe fruits and vegetables to use; you will find that many of these are the same as first weaning foods in a normal diet e.g. carrots, apple, pear, banana and sweet potato. However, it is recommended that you always check the protein content of new foods before introducing them into your baby’s diet.

You will also be taught how to read food labels so that you can choose appropriate low-protein baby foods from the supermarket. You may also be given a prescription for some specially produced low-protein prescription foods. 

Top tips for getting started

  • Choose a nice, quiet time to offer solids so that you and your baby are relaxed. Your baby must be supervised at all times when eating
  • Use a high chair or booster seat which can clip onto an ordinary chair to lift your baby up within reach of the table. Use a plastic weaning spoon to feed with and give another spoon for your baby to hold
  • Start by giving a very small amount (1-2 teaspoons) of low-protein solids once per day after a breast or formula feed, and build this up at your baby’s pace 
  • Don’t force your baby to eat, wait until the next feeding time if they do not seem interested. If your baby sticks his or her tongue out when the food approaches instead of opening their mouth, they might not be quite ready 
  • Try to include a wide variety of low-protein weaning foods early in the process
  • Cool hot food, stir well and check the temperature of the food before giving to your baby 
  • Don’t be afraid to get messy! Babies learn about food by touching, smelling and tasting

Making your own low-protein purées at home 

Why not try to make your own purées at home? Homemade purées are cheap and easy to make. Fruits and vegetables can be cooked in a small amount of water until soft and then puréed using a hand blender or food processor. Set aside a day to prepare a few batches, then freeze it in ice cube trays. Once frozen pop into freezer bags, making sure that you label the bag with the type of food and the date it was made. The frozen cubes give you easy to serve portions for meal times. Remember:

  • Never add salt or sugar to homemade purées – your baby’s tastes are different to yours!
  • Many low-protein weaning foods are also low in calories; try adding a little butter or vegetable oil to homemade purees and speak to your dietitian about using specially produced low-protein prescription foods to increase the energy content of your homemade solids.

Moving through the stages 

Once your baby is taking low- protein solids well, your dietitian will likely advise you on gradually introducing Phe / protein containing foods into the diet. These are known as ‘exchanges’, as the Phe / protein your baby was getting from breastmilk or infant formula is gradually exchanged for Phe / protein from solids.

1 exchange = 50mg Phe = 1g protein

Your dietitian will give you a list of food weights or measures which correspond to 1 exchange. They will also teach you how to read food labels, so that you can weigh out your own exchanges. 

As you progress with weaning, you will be able to gradually introduce more textures into your baby’s diet. Starting with thicker purées, and working up to lumpier, mashed and then chopped food. Your dietitian will be able to advise you as to when is to right time to introduce more complex textures into your baby’s diet.

Low-protein finger foods

It is a good idea to encourage soft, low-protein finger foods alongside puréed foods from around 7 months of age, or when your baby is ready. Ideas include fingers of low-protein toast, parboiled carrots, soft fruits (such as strawberries, peach, banana) or homemade sweet potato chips. Don’t worry if most of this ends on squished between fingers or on the floor to begin with – it is all part of the learning process!

A little down the track, when your baby has learnt how to eat low-protein finger foods reliably, you can start to introduce exchanges as finger foods. Speak to your dietitian for more information.

Second stage protein substitute

Around the time of weaning, your dietitian will likely introduce a more concentrated protein substitute alongside the Phe-free infant formula; this is known as a ‘second stage protein substitute’. This is needed because as your baby eats more solids, their intake of Phe-free infant formula decreases. At the same time protein requirements are increasing with growth. Speak to your dietitian for more information.

The second stage protein substitute is often in the form of a paste, and can be given with a spoon prior to solids. Alternatively, the Phe-free infant formula may be made more concentrated with the addition of another product. Your dietitian will give you a plan on how to introduce this.

For more information about protein-free infant formula and protein substitutes, visit the Products section of the website.

What should I do if my baby doesn’t eat? 

All babies have ‘off days’ just like us and in most cases this is perfectly normal. Don’t make a fuss or try to force-feed your baby. Just clear the food away and try again at the next mealtime. When food is taken offer lots of praise and encouragement. Try to make mealtimes fun, offer a variety of foods suggested by your dietitian and ensure portions are small and manageable. If you have any concerns about your child’s eating, speak to your dietitian for guidance.

Where can I find more information?

Your dietitian will give you all of the information you need for successful weaning. We also have a weaning guide and the following weaning video available.

Please Note: The dietary management for PKU varies for each person so all information presented here is for guidance purposes only. The information provided on this page is in no way intended to replace the care, advice and medical supervision of your healthcare professional.Your own dietitian and/or doctor will advise you on all aspects relating to management of PKU for you and your family Always consult your healthcare professional before making any changes to your child’s low-protein diet.

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