LowproteinLIVING

The only way to treat PKU is to restrict the amount of phenylalanine entering the blood. A PKU diet avoids food and drink that contain large amounts of phenylalanine.

There are certain foods that must be avoided:

• Meat.
• Poultry
• Fish
• Eggs
• Cheese
• Pulses (beans and lentils)
• Meat substitutes (e.g. soya products and Quorn™)
• Nuts.

These are the foods that are high in protein.

There are foods that can be eaten freely (known as free foods):

• Most fruits
• Some vegetables
• Salad
• Sugar
• Spices
• Herbs
• Oil
• Margarine
• Butter

Special low protein foods such as bread, pasta and biscuits can be prescribed by doctors and used in the normal way.

To understand your PKU diet you must remember the following dietary principles
• The aim of the PKU diet is to keep blood phenylalanine within the recommended ranges. This is done by restricting the amount of phenylalanine you eat.
• Protein contains phenylalanine. Eating foods high in protein will increase your blood phenylalanine.
• The diet must still provide a small amount of phenylalanine for body growth and repair.
• As with any diet it must also contain enough energy and nutrients to keep you healthy.

Avoiding high protein foods without doing the rest of the diet is unsafe. You need to get your protein from:

• The protein substitute which provides no phenylalanine
• The exchanges providing just the right amount of phenylalanine.

Although they can be similar the PKU diet is not the same as a vegetarian diet. Vegetarians will avoid meat and sometimes all animal products, however they get their protein from nuts, beans and pulses.

Your prescribed protein substitute will replace the protein and nutrients found in foods like meat and fish. It also provides all essential “safe” protein without the phenylalanine. The substitute should be taken regularly over the day during or immediately after meals or snacks (please refer to your dietitian). The more frequently you take your supplement, the better your phenylalanine control will be.  Some substitute formulas already contain the essential vitamins and minerals, others require you the vitamins and minerals to be taken separately.

If you frequently miss taking your protein and vitamin substitute you are at risk of serious deficiency problems. Missing your substitute will cause your blood phenylalanine levels to increase.  If you feel you cannot keep taking your substitute please contact your doctor or dietitian to discuss the alternatives.

Protein in the PKU diet comes mainly from a special supplement drink or bar taken with a meal. The diet also contains weighed amounts of moderate protein foods called exchanges. Examples of exchange foods are bread, potato, cereals and rice.

Foods such as cereals, some vegetables and milk contain small amounts of protein. These foods are allowed in the diet in weighed amounts called “exchanges.” This provides a controlled intake of phenylalanine needed for body tissues to grow and function normally.  Your dietitian will advise you on how many exchanges you can take. This will depend on the amount of phenylalanine in your blood and can change according to your needs.  It is important to take the exact number of exchanges recommended and spread them out as evenly as possible over the day.  For best results aim to weigh out your exchanges with scales at least once a week. This is to keep familiar with portion sizes.

Eating more exchanges than you have been recommended will raise your blood phenylalanine levels.

Foods such as some vegetables and fruits, fats and sugars are naturally low in phenylalanine. These can be eaten in normal amounts. Specially manufactured low protein foods such as bread and pasta are available on prescription. These can be eaten freely.  These foods make up the majority of the diet in the place of higher phenylalanine alternatives.  Low protein starchy foods such as bread “bulk out” the diet and provide an important source of energy and satisfy hunger. Low protein prescription foods are useful for increasing the variety in your diet and help to keep it interesting.