Phenylketonuria and Exercise

Phenylketonuria and Exercise

Patients with phenylketonuria (PKU) are unable to metabolize phenylalanine, a protein building block, also called an amino acid.

They have to be extremely careful to maintain a low-phenylalanine diet. This restrictive diet can make it difficult for patients to maintain a healthy weight and strong bones, or to lose weight and build muscle. Exercise can help.

Is exercise safe for people with PKU?

Exercise is safe and recommended for people with PKU. However, if you do not exercise regularly, you should talk with your doctor and a physical fitness coach before starting. This will help ensure that the exercise program or sport you choose is safe and best for you, and if you need to work up to it.

What benefits might exercise bring?

Exercise can help maintain physical fitness, mental health, and overall wellness, as well as assisting in keeping a healthy weight and strengthening your bones. Physical exertion can also give you more energy and help you to sleep better.

What care should be given as I start exercising?

Make sure that you confirm with your doctor that you are physically able to start the exercise program or sport you would like to participate in.

It is also important not to overdo exercise. It’s easy to hurt yourself in the gym or while working out if you haven’t exercised in a while. That’s why it’s best to build up slowly.

Avoid protein powders and shakes, even if your gym encourages them. Speak with a registered dietitian who is aware of your PKU diagnosis before adding any protein shakes or other supplements to your routine. Most commercially available protein shakes contain high levels of phenylalanine as well as other amino acids.

Is there evidence exercise helps with PKU?

Exercise is important for everyone’s health, but few studies have specifically examined exercise as a way of managing PKU.

A small study in nine PKU patients tested whether acute exercise (one 30-minute aerobic session) affected their blood phenylalanine levels. The study failed to show any improvement in phenylalanine levels following the exercise. It is possible that a longer exercise program, one lasting several weeks or months, is needed for PKU patients to show changes in blood phenylalanine levels, and pre-exercise meals might need to be more controlled.

A clinical trial (NCT04302285) evaluated blood levels of phenylalanine and metabolic rates in up to 16 adults with PKU before and after a single one-hour exercise session and disease-specific meal, compared with those given the meal alone. This study is thought to have finished in July 2019, but results have not yet been published.


Last updated: Aug. 6, 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.

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