Your dietitian will always help you select the most appropriate protein substitute to meet your child’s needs.

Protein substitutes for PKU are available on prescription and are provided from your doctor or nurse practitioner. Supply can be organised through a local pharmacy or by contacting the company directly; most offer a home pharmacy service with free delivery.  Prescriptions are valid for 6 months (or slightly longer) assuming you order supply every month.  If change to a different protein substitute is needed, a new prescription is required.

As part of your baby’s special low protein diet your baby will be taking a phe-free formula (a protein substitute); it contains all the amino acids your baby needs to grow and develop normally, without phe.   It also contains carbohydrate, fat, vitamins, minerals, and other nutrients your baby needs.  This phe-free formula is in a powder format and comes in a can. It is mixed with water, in the same way as standard infant formula. Your baby will also need a certain amount of natural protein, this is provided by either breastmilk or standard infant formula.

Initially, if your baby’s phe levels were very high, you would have been advised to feed your baby solely with the phe-free formula for a few days. This is to allow the phe levels in the blood to fall quickly to within the normal range. Usually after a few days natural protein is reintroduced in measured amounts and is given as breastmilk or standard infant formula.  Breastfeeding your baby is encouraged if possible.

As your baby grows, the amount of phe-free formula, breastmilk, or standard infant formula, will change.  Your dietitian will advise and support you, each time a change is needed.  

The phe-free formula is available on prescription; which is written by your doctor or nurse practitioner.  If your baby changes to a different phe-free formula, a new prescription is needed. 

Your dietitian will introduce a more concentrated protein substitute (a second stage protein substitute); it contains more phe-free protein in a smaller volume.  Second stage protein substitutes are available as powders in sachets (or tins) and ready prepared liquids.   

For babies aged 6 months, second stage protein substitutes, available as powder, are usually presented in sachets.  They can be mixed with a small volume of water to form a very low volume, semi-solid; which has a very smooth consistency and can be given off a spoon, or they can be mixed with a larger volume of water and taken as a drink.

Whilst your baby is under 1 year of age, they will be advised to take an unflavoured second stage protein substitute. These taste familiar to them, which helps with the transition to a new formulation. Different flavours can be offered after 1 year of age if desired.

Your child will usually remain on this protein substitute until they are ready to go to school or your dietitian deems it necessary to move them onto a new protein substitute, usually between 3-5 years.

As your child grows, the amount of protein substitute prescribed will increase.

At this age, ready-to-drink protein subsitutes may be introduced - these are generally convenient to use at school and when away from home. Alternatively, powders which can be mixed with water to make a drink, are available.

Ready-to-drink protein substitutes come in different sizes, so as your child gets older and their protein requirements increase, they can just swap the size of their protein substitute, rather than needing to change to a completely new one.

These protein substitutes come in a variety of different flavours, your child may find a favourite or prefer to mix and match.

They may wish to change protein substitute for any manner of reasons including:

Convenience – a change in circumstance, such as work or going to university.

Travel – powdered protein substitutes and tablets are lighter to carry than a ready-to-drink liquid.

New products – from time to time, new protein substitutes and new flavours become available. Some people are keen to try new products whilst others are happy to stick with the one they are familiar with.

Better meet nutritional needs- your dietitian may suggest a change so to better meet your body’s nutritional requirements ie; a protein substitute providing less calories

Boredom/Wanting a change – taking the same flavoured product, 3/day, 7 days/week suits some, others like to vary their diet.  

Pregnancy – is a very special and exciting time although at times it can be daunting and frustrating. Following a very strict low protein diet, both before and during pregnancy, is very important for the female with PKU so to keep blood phe within the normal range for pregnancy.  Taking the protein substitute consistently during this time is crucial.   For mild sickness and nausea, compliance to diet may improve with a different protein substitute; one that seems more palatable.    Other recommendations include, drinking smaller amounts, more often, and trying different flavours.  Your dietitian will advise on the amount of protein substitute you will need over the stages of your pregnancy and assist you with changes to protein substitute if they are needed. Your dietitian will help guide you every step of the way so to achieve a healthy baby.