Low-Phenylalanine Diet

Nutritional approach

Phenylalanine is an amino acid found in many proteins in the body (tissues, hormones, bones, etc.). These proteins are also present in many of the foods we eat.

Phenylketonuria is a hereditary metabolic disease, usually diagnosed at birth, characterized by an inability by the body to effectively process phenylalanine. If a low-phenylalanine diet is not initiated in the early weeks of life, phenylalanine levels build up in the child's blood, causing significant brain damage. By managing phenylalanine levels through diet, children can develop normally.

Dietary guidelines

• It's important to maintain a low-phenylalanine diet, which is possible by following these guidelines:
  • Avoid foods that are naturally high in protein.
  • Choose mainly low-protein foods.
  • Limit all sources of aspartame.
• This diet should be supplemented with a nutrition formula containing little or no phenylalanine. Doing so is essential to avoid significant protein, vitamin, and mineral deficiencies.
• A small amount of phenylalanine is necessary for normal growth and body function. Regularly monitoring blood phenylalanine levels through blood tests is essential to determine what amount is safe for each individual.
• Qualified health care professionals can help those affected choose the right nutrition formula and adapt their diet.
• This diet must be maintained for life.

Guidelines for newborns

• A newborn's diet should consist of modified-amino acid formula containing little or no phenylalanine.
• Feeding the baby a small amount (calculated by a nutritionist) of breast milk or a regular commercial infant formula can ensure that their minimum phenylalanine requirements are met.
• Low-phenylalanine foods can be introduced once the baby is ready to start eating solids.
• Qualified health care professionals can help determine the safe amount of phenylalanine for the baby and make recommendations for a varied, balanced diet.

Avoid naturally high-protein foods

The following are examples of foods to avoid:

• Meat and poultry
• Fish and seafood
• Dairy products
• Soy (tofu and other soy derivatives)
• Legumes (e.g., red kidney beans, lentils, chickpeas)
• Eggs and nuts

Eat mainly low-protein foods

These foods should be eaten at every meal to ensure a balanced diet:

• Low-protein grain products
• Fruits and vegetables prepared in different ways (e.g., raw, grilled, in soup)
• Adapted nutrition formulas: essential to meet protein requirements
  • Some nutrition formulas contain protein hydrolysates from which phenylalanine has been partially or completely removed.

The following foods are also low in phenylalanine. They can therefore be consumed as part of a balanced diet:

• Water
• Sugar and salt
• Spices and oils

A variety of low-protein foods are available on the market. These are more expensive, but can add variety to a low-phenylalanine diet. It is recommended to read the label and/or consult a nutritionist before consuming these products.

Limit all sources of aspartame

Aspartame is a sweetener that contains phenylalanine. It should be avoided.

• Equal, and other sweeteners, often found in the following foods:
  • Drinks
  • Yogurt
  • Cereal
  • Desserts
  • Chewing gum
  • And more: be sure to read labels carefully

Choose the right foods

These measures will help reduce your phenylalanine intake while ensuring a healthy diet.

• Foods to eat often:
  • Apples, grapes, and berries instead of bananas
  • Soups made with vegetable broth instead of dairy products
  • Spaghetti squash instead of pasta
  • Plant-based beverages (e.g., rice and almond milk) instead of cow's milk
  • Mashed cauliflower instead of potatoes
  • Coconut yogurt instead of regular or soy yogurt
  • Sautéed and seasoned vegetables instead of ground meat
• Foods to eat in moderation:
  • Added sugar: honey, jams, candies, sweet drinks, cakes
  • Salt: prepared foods, pickles, chips
  • Trans and saturated fats: palm oil, fried foods, hydrogenated vegetable oils

If you have any questions about the phenylalanine content of other foods or would like information about suitable cookbooks, speak to a nutritionist.

Meeting regularly with specialists will help you adapt this diet to your health condition and needs.

Always watch your diet: