You can build muscle with PKU

We spoke to Sarah Anderson, Senior Dietitian in Metabolism, who gave us more insight into how to build muscle with PKU on a low protein diet. Muscle building and exercising with PKU is absolutely possible—it's all about how and when you do it.

Nutrition plays a crucial role in sports performance, as it provides the fuel your body needs to achieve your fitness goals. According to Sarah, optimal nutrition supports the metabolic and physical demands of training and tailored nutritional strategies can help to reduce fatigue, optimise training and reduce the risk of injury.

Sarah says:

"There are several nutritional techniques that can help PKU patients support their training goals and improve their athletic performance while following a low-protein diet."

Three frequently asked questions among PKU professionals about sport and nutrition are:

  • How can I build muscle with PKU?
  • Should I take protein supplements?
  • What is the best way to recover after exercise?
  • But first, let's look at the importance of protein in PKU.

 

Proteins and PKU

Protein is essential for tissue repair and muscle growth. Although there is little specific research on muscle building and sports nutrition on a low-protein diet, we can use the existing evidence to have a good conversation with your dietitian.

1. How do you build muscle with PKU?

Sarah:

"In short, you need enough calories to supplement your energy expenditure and enough protein for muscle recovery and building. For most people who exercise recreationally and want to maintain a healthy weight, a varied diet with plenty of fruits, vegetables, complex carbohydrates and the right amount of protein substitutes is sufficient."

How much protein does an athlete need?

Sarah explains:

"Athletes without PKU, including strength and endurance athletes, typically need 1.2 – 2.0 g of protein per kg of body weight per day. This is 50-250 percent more than a non-exercising person without PKU, who needs 0.8 g of protein per kg of body weight per day."

"For an adult with PKU, the protein recommendation is 0.8 g of protein per kg of body weight per day, plus an additional 40 percent to control the digestibility of amino acids and phenylalanine. This equates to 1.12g of protein per kg per day for a sedentary adult with PKU."

Timing is everything

Sarah:

"The timing of protein consumption plays a big role in muscle building. Protein is most effective for muscle growth when taken within two hours of exercise and distributed at regular intervals throughout the day."

Muscle growth is stimulated for at least 24 hours after resistance training, sprinting and endurance training. The muscles are extra sensitive to proteins during this period.

The ideal amount of protein immediately after exercise is around 15-20 g of protein (or about 10 g of essential amino acids).

PKU protein substitutes often contain 20g of protein equivalent, 10g of which are essential amino acids, making them ideal for muscle recovery. Taking more protein than necessary has no additional benefits and may even be detrimental to kidney function. However, older PKU people or those with low protein stores may benefit from slightly higher doses.

2. Should I take protein supplements?

What role do amino acid mixtures play in muscle growth?

Muscle building comes from the essential amino acids in protein. PKU protein substitutes are rich in essential amino acids, which makes them ideal for muscle growth.

Sarah gives an example:

"An 80 kg athlete needs 1.2–2.0 g of protein per kg of body weight per day, which equates to 96–160 g of protein per day."

Let's say your daily amount of natural protein is 6 g. You would then need 5 20g servings of a phenylalanine-free protein substitute to meet your total protein needs.

For optimal muscle growth and recovery with PKU, it is important to spread your daily protein intake throughout the day and take it immediately after an intense workout.

Recommendations for a good nutrition plan:

  • Have a protein substitute with every meal
  • Take a protein substitute immediately after exercise
  • Take a protein substitute before bed
  • Distribute natural proteins from food substitutions to main meals or use them as a snack before or after exercise

 

Important: Make sure you have a varied diet with enough energy to maintain a healthy weight. Protein substitutes immediately after exercise and regularly throughout the day are key to muscle growth.

3. How do you improve recovery after exercise with PKU?

Sarah:

"If you exercise for less than an hour, your muscle glycogen stores are not depleted and you can support your recovery with your regular meals, protein substitutes and snacks. With longer or heavier workouts, or if you train several times a day, good recovery becomes even more important."

A good recovery plan will help you:

  • Replenish energy and fluid stores
  • Promote muscle recovery and growth
  • Adapt your body to training
  • Support your immune system

 

Recovery tips from Sarah:

  • Drink enough water to stay hydrated
  • Eat a combination of carbohydrates and protein within two hours of exercise
  • Opt for complex carbohydrates such as low-protein pasta, rice, or bread
  • Add a small amount of natural protein to meals or snacks
  • Have a high-carb snack before or immediately after exercise

 

Your optimal diet depends on:

  • The type of sport you practice
  • Your personal sports goals
  • Your training frequency and intensity
  • Your body composition and fitness level
  • Your dietary preferences and PKU needs
  • Consult with your dietitian to get a customized nutrition plan that fits your activities and goals.

 

Key points

  • You can build muscle and stay healthy with PKU
  • Your protein substitutes support your sports and training needs
  • Consistency is key: take your protein substitutes at regular intervals throughout the day
  • Take a combination of carbohydrates and protein substitutes immediately (or within two hours) after exercise
  • Always consult with your treating dietitian before making any changes to your diet
  • Whether you're working out at the gym or climbing a mountain, it's good to know that PKU doesn't have to be a limitation. Put on your sneakers and go for it.

 

Credentials: 

Beelen M, Burke LM, Gibala MJ, van Loon LJ. (2010) Nutritional strategies to promote post-exercise recovery. Int J Sport Nutr Exerc Metab. 20 

Burd NA, West DW, Moore DR, et al. (2011) Enhanced amino acid sensitivity of myofibrillar protein synthesis persists for up to 24hr after resistance exercise in young men. J Nutr. 141(4):568-573 

Phillips, SM (2014) A Brief Review of Critical Processes in Exercise-Induced Muscular Hypertrophy. Sports Med. 44 (Suppl 1): S71-S77 

Thomas, D.T., Erdman, K.A. and Burke, L.M. (2016) Position of the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine: Nutrition and Athletic Performance. J Acad Nutr Diet. 116(3): 501-28 

Tipton KD, Ferrando AA, Phillips SM, et al. Post-exercise net protein synthesis in human muscle from orally administered amino acids. Am J Physiol. 1999; 276:E628-34. 

Van Spronsen FJ et al. (2017) Key European Guidelines for the diagnosis and management of patients with phenylketonuria. Lancet Diabetes Endocrinol Jan 9  

http://www.thelancet.com/journals/landia/article/PIIS2213-8587(16)30320-5/abstract 

About the author

Disclaimer
The opinions/views presented are solely those of the person themselves and do not necessarily represent those of Nutricia. This article does not constitute medical advice or professional services. Consult your doctor and dietitian before making any changes to your diet or protein intake to ensure the right nutrition to support your unique needs.