Low Protein Diet

The foods we eat contain different types of nutrients including carbohydrates, fats and proteins. For individuals with PKU, protein is the nutrient which is most important.

What is protein?

Protein is needed for growth. Foods which are high in protein include meat, fish, eggs, nuts and pulses. Some carbohydrate-based foods like flour, pasta and rice also contain small amounts of protein, whilst most fruits and vegetables are naturally low in protein.

Proteins are made up of small units or building blocks called amino acids. There are about 20 different amino acids, 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) and is found in nearly all types of protein.

What is PKU?

PKU is a genetic condition. In individuals with PKU, phe can’t be broken down in the body so it builds up to high levels in the blood. This is toxic to the brain.

To prevent the levels of phe becoming too high, the diet needs to be very low in phe ( just enough to provide the amount required to support growth and development).

Diet for PKU

Keeping phe levels low can be achieved by following a very low protein diet. The individual will also require a protein substitute and a small amount of natural protein.

Individuals with PKU can eat foods naturally very low in protein freely, as well as specially made low protein foods.

There are four components to the diet for PKU:

Protein Substitutes

The protein substitute provides the amino acids (except phe) as well as, in many cases, vitamins, minerals and fatty acids.

Protein intake is extremely restricted in the diet, but individuals with PKU still need to meet their daily protein requirements to grow and develop normally; therefore, a protein substitute is taken.

The correct amount of protein substitute each day, as well as the most suitable type, will be decided upon by the dietitian.

Phe Exchanges

Those with PKU still need a very small amount of natural protein to support their growth and development. To provide this small amount of protein, an exchange system is used where 1g of protein equals 1 exchange (1 exchange provides 50mg of phe).

The number of exchanges allowed in the diet each day will be dependent upon the person’s individual phe tolerance. This will be decided upon by the dietitian.

Specially Made Low Protein Foods

There are specially made foods that are low in protein (and therefore low in phe), these include:

Low Protein Bread
Low Protein Pasta
Low Protein Rice
Low Protein Flour Mix
Low Protein Milk Alternatives

These items are available on prescription and are useful to provide energy and variety in the diet.

Exchange-free Foods

Certain foods contain very little or no phe and can be given without counting towards phe exchanges.

These foods are classed as exchange-free and help to provide energy in the diet. exchange-free foods include certain fruits and vegetables, oils, fats and sugars.

Speak to your dietitian or refer to the NSPKU dietary information booklet for details of foods that are exchange-free.

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