Keeping a Phenylketonuria Food Diary

Keeping a Phenylketonuria Food Diary

As the caregiver of a child who has phenylketonuria (PKU), you know that your child requires a nutrition plan that restricts certain foods. Maintaining a PKU food diary can help keep track of what your child eats.

What is PKU?

PKU is a metabolic disorder characterized by increased levels of phenylalanine, an amino acid obtained through diet. (Amino acids are the  building blocks of proteins.) Phenylalanine is present in all proteins and in some non-protein foods, such as soda pop and artificial sweeteners.

PKU patients lack an enzyme to properly process phenylalanine. That’s why  they need to have a lifelong low-protein diet.

PKU diet

Ideally, a low-protein diet is free of foods such as dairy, meat, fish, chicken, eggs, beans, nuts, pasta, chocolate, soybeans, and bread, as well as any products made from these foods. Consuming protein-rich foods causes phenylalanine to accumulate in the body, resulting in damage to nerve cells in the brain.

Why is a food diary necessary?

A major part of managing PKU is recording what your child is eating and drinking so that their phenylalanine intake stays within daily limits. A simple way to do this is to keep a food diary. The food diary also can help your child’s dietician determine whether dietary adjustments are needed. In addition, when the PKU team asks for a blood sample, they typically want to see a diet record, too.

What do I need to create a food diary?

First, you will need measuring tools such as a food scale and spoons. Not measuring your portion size accurately can mean your child is taking more phenylalanine than you think. If such tools aren’t available, temporarily characterize the food amount as a “handful” or the approximate size of a fist or thumb.

You also need to create a form with headings. As long as it’s legible, the log can be as simple as crude lines drawn on paper, with spaces for subjects.

What should a food diary include?

  • Date and time: Record the date and time your child consumed a drink or food, including medical food.
  • The type of food or liquid consumed: Record this and be specific. For example, write “orange” instead of “fruit.”
  • Amount eaten: Record specific measurements such as grams, teaspoons, or cups. If your child had “three bites,” write that. The amount is as important as the type of food your child ate.
  • Amount of phenylalanine: Look up the applicable amount of phenylalanine in your food reference guide and log the quantity that matches the amount of food your child ate.
  • Amount of proteins and calories: Record the amount of protein and calories in foods your child consumed, if available. For patients with PKU, the most important nutrition facts listed on a product’s label are serving size (in grams or pieces) and amount of protein (in grams).
  • Daily totals: Record the total phenylalanine, protein, and calories (if available) that your child consumed that day. It may be helpful to tally the phenylalanine as you go so that you can see how much your child has consumed so far. This will help you figure out how much more they can eat to stay within the daily limit.


Last updated: April 16, 2020


Phenylketonuria News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website

How useful was this post?

Click on a star to rate it!

Average rating 0 / 5. Vote count: 0

No votes so far! Be the first to rate this post.

As you found this post useful...

Follow us on social media!

We are sorry that this post was not useful for you!

Let us improve this post!

Tell us how we can improve this post?