No matter the reason for the special diet, it’s important that your child has the nutrients they need for growth, health and energy.

It is also useful to know that special diets prescribed for genetic conditions or allergies are not suitable for other members of your family. For children with a metabolic condition or allergy, it is important to stick to the diet and not see non-diet foods as ‘treats’.

Diets for special disorders from birth

If your baby is born with a genetic condition that affects their ability to deal with a particular nutrient, they will need a special diet for life.

A qualified dietitian can help with such diets so your child can enjoy healthy foods and avoid foods that will cause them problems.

In Australia, all babies are tested at birth for PKU, or phenylketonuria. Babies with PKU lack an enzyme needed to break down one of the amino acids (phenylalanine) in protein. High levels of the amino acid can lead to problems with development of the brain.

If your baby tests positive for PKU, they will to need eat low protein diet and foods with low levels of the particular amino acid throughout life.

Another genetic condition tested in newborn babies is galactosaemia. Babies with galactosaemia lack an enzyme needed to break down the sugar galactose, which is found in breast milk as well as milk from cows, goats and sheep. People with galactosaemia must avoid foods made with milk or milk products their whole lives. Soy products and mature cheese are permitted.

Food allergies

If you think your child may have an allergy, your doctor can confirm it with a skin prick test or a blood test. The most common allergies are to:

• eggs
• peanuts
• nuts that grow on trees
• sesame seeds
• wheat
• soy
• milk

Most but not all children outgrow their food allergies. But as long as they have the allergy your child will need to avoid the foods that trigger a reaction.

Food intolerance

Unlike allergies, food intolerances do not involve the immune system and generally do not cause severe reactions. The most common intolerances are to lactose (in milk), and gluten (a protein found in grains such as wheat, rye and barley).

Your doctor will do tests to diagnose food tolerance and advise on the next steps depending on the findings.

Vegan and vegetarian diets

Vegetarian and vegan diets may be low in certain nutrients including vitamins such as vitamin B12, which is found only in animal products and minerals. Check with an accredited practising dietitian that your child’s diet provides all the nutrients they need for healthy growth. You might need to give your child supplements to cover any shortfall.

A well-balanced vegetarian diet shouldn’t cause any nutritional problems. Meat, fish or poultry can be replaced by legumes, tofu, seeds and nuts.

A vegan diet needs careful planning for children when it excludes the following:

• meat
• fish
• poultry
• milk
• cheese
• yoghurt
• eggs

Sticking to the diet when not at home

It can be difficult to explain to children that they need to stick to a special diet. But it is important that they understand as early as possible.

You can help them stick to their diet when out of the home by writing a simple list of what’s acceptable food and what’s not. You can put that list on the fridge, give it to childcare and school, and make sure that friends know about what you child can and can’t eat.