Returning to diet

Returning to a low protein diet following a period of being off diet or making your low protein diet healthier is beneficial at any age. It can be tough to adjust your eating habits but very worthwhile. Regaining control of your Phenylalanine (Phe) levels can help reduce the negative effects from high Phe levels; such as tiredness, difficulty concentrating, and mood changes.

It's never too late

"When I was a teenager, I JUST WANTED TO BE LIKE EVERYONE ELSE. It started with pouring my protein substitute in the sink, then before I knew it, I was off diet. Since I could not immediately ‘feel’ my PHE levels going up, I didn’t realize the changes that were happening. My grades got worse, my attitude and mood got worse. I was always tired and felt foggy. When I went back on diet it was like the fog had lifted. "

Katie, 31 PKU

Some low protein myths!

I can manage my PKU by just eating low protein foods without taking a protein substitute

The Truth is people with PKU need to have a PHE-free protein source in their diet. A PKU protein substitute is a special modified protein source made specifically to help manage PKU and make sure that your low protein diet is nutritionally balanced.

All PKU protein substitutes and low protein foods taste bad

The truth is PKU protein substitutes have changed a lot in recent years. PKU protein substitutes come in a variety of flavours, forms and styles. You can have a ready-to-drink protein substitute that you can take on the go, or a powder that mixes with a very small amount of water so you have less-to-drink. See our product pages for more information or speak to your dietitian to learn more about all PKU protein substitute options.

I have to drink a lot of protein substitute to get the full amount of daily protein I need.

The truth is PKU protein substitutes come in different forms and various lower volume, more concentrated options are available. See our product pages for more information or speak to your dietitian to discuss the different options.

I’m too old to go back to drinking a PKU protein substitute.

HONESTLY, IT IS NEVER TOO LATE. Regaining control over your PKU diet at any age can help reduce the negative effects PKU can have on you; such as tiredness, difficulty concentrating, and mood changes.

"I went off diet mostly because MY PROTEIN SUBSTITUTE JUST TASTED SO BAD. Years later I tasted one of the newer protein substitutes at a PKU event and thought, WOW!… this stuff is not too bad. I made the commitment to GO BACK ON DIET and have never felt better."

Dan, 30 PKU

PKU the facts – let’s refresh

What is PKU?

Phenylketonuria (PKU) is a genetic disorder that a person inherits from both parents. PKU occurs due to a deficiency of the enzyme phenylalanine hydroxylase (PAH). This enzyme deficiency interferes with a person’s ability to metabolize or process the amino acid phenylalanine (PHE) into tyrosine (TYR), another amino acid.

Amino acids, like PHE, are the building blocks of protein found in food and the human body. Consuming too much PHE from food can lead to a toxic build-up of PHE in the blood and brain of a person with PKU and over time this can cause irreversible brain damage (especially seen in children). Presently, there is no cure for PKU, but it can be managed effectively with the combination of a low protein diet and intake of protein substitutes specifically designed for people with PKU.


PHE build-up (high levels) and/or low levels of TYR can cause

  • Difficulty concentrating
  • Feeling tired, moody or in a fog
  • Tremors in hands, fingers, feet or legs
  • Poor memory, short term recall or general forgetfulness
  • Trouble focusing at work or school
  • Difficulty following directions and problem solving
  • Anxiety, phobias or depression

Many of the problems associated with being off diet can be minimized or may go away once your blood PHE levels are back in an acceptable range.

Why do I need a low protein diet?

A low protein diet is needed to avoid the dangerous build-up of PHE and the symptoms that can occur when PHE levels are high. See above where we talked about signs and symptoms of high PHE and/or low TYR levels. Many teenagers and adults with PKU report feeling better when on a low protein diet.

What is a low protein diet?

A low protein diet is a diet that is low in natural protein to make sure that you get just the right amount of PHE; not too much to cause high blood and brain PHE levels, but also not too little as some PHE is necessary for normal body functioning.

All foods (other than pure fat, oil and sugar) contain a certain amount of protein and therefore PHE. Meat, chicken, fish and dairy are examples of foods high in protein and PHE but other common foods such as bread, pasta, rice, potato, corn and peas also contain a fair amount of protein and PHE. Learning which foods are high in PHE and which are low will help with your long-term diet management.

However, just eating a diet low in natural protein will not meet the body’s requirement for protein. So, to meet total protein requirements, the PKU diet also needs the inclusion of PKU protein substitutes. PKU protein substitutes provide a ‘safe’ source of protein, as they contain protein but little or no PHE.

Most fruits and vegetables are naturally low in protein and should make up the bulk of the PKU diet. There are also special low protein foods, which are available on prescription, that have been modified to be lower in protein than their usual store-bought counterparts.

These special low protein foods, such as low protein pasta, bread, rice, cereals and baking mixes provide more variety and can make the PKU diet more appealing and interesting. If you are interested in trying some low protein foods or learning more about what is available, please visit the low protein section of our website or speak to your dietitian who will be able to request samples for you.


What first steps can I take?

  1. Tell your family and friends. Talk to those closest to you about your dietary needs and goal to return to diet. This will help you develop a team of people to support you as you get back on diet or want to improve your current PKU diet.
  2. Call a metabolic clinic to make an appointment. A dietitian will work with you to develop a personalised plan to help you get back on the PKU diet.
  3. With the help of your dietitian, find a PKU protein substitute that fits your lifestyle.
  4. Meet other people with PKU, join a Facebook group, or attend a PKU event or conference.
  5. Fall in love with fruits and vegetables. Explore new items at your local market and look into new recipes online and in vegetable-focused cookbooks. Check out our recipe pages for some inspiration.
  6. Don’t be afraid to make the changes at your pace. You don’t need to change everything overnight. Take things one step at a time, so that you can make changes that last.
  7. If you stray off the diet, don’t give up! It’s difficult to have a perfect diet all the time, so keep trying and eventually it will become part of your daily routine.

Where do I get a quality source of protein?

Your PKU protein substitute is your main source of protein per day. Look at it as a special protein shake that contains a modified protein source specifically designed for those with PKU. The protein is a blend of amino acids that contains very little or no Phenylalanine and is supplemented with Tyrosine, the amino acid that individuals with PKU can only make in small amounts. Your PKU protein substitute must be used as prescribed by your healthcare professional.

Your protein substitute will make up the majority of your daily protein intake. Your healthcare professional will be able to advise you on the amount that’s perfect for you and arrange a prescription for a protein substitute that suits your needs.

PKU protein substitute options for adults

  • Powders
  • Liquids
  • Mousse style
  • Tablets

Protein substitutes all have different features, with varying formats, calories, volume and a wide range of different flavours.

Calories: Protein substitutes are available with varying amounts of calories, so speak to your healthcare professional about one that best suits your needs.

Volume: Many protein substitutes can be made up with varying amounts of water so you can have a smaller volume, more concentrated drink or a more dilute tasting larger volume drink, depending on your taste preference. Your dietitian or clinician will be able to advise you further on this.

Flavours: Protein substitutes come in a wide variety of flavours.

See the individual products in the product section of our website for more information on all the formats mentioned above.

If you would like any further information, please speak to your healthcare professional or email


What works for me

"I take a mix of Lophlex products which gives me variety, choice and flexibility. In the morning, depending on my mood, I take Lophlex Sensation (berry flavour) or 2 pouches of Juicy Berry or Citrus (both 10s). Mid-morning and lunch and mid-afternoon in work, I take a pouch of Juicy Berry (kept cool in a cooler bag), and at home before dinner I take another 2 pouches or a Sensation pot. I find the 10s size perfect for spreading out my protein substitute during the day, and when travelling abroad I can take it through airport security as hand luggage without any problems." 

Brendan, 38, accountant working in financial services

Tips for making PKU protein substitute part of your life

Make a daily routine

  • Your body functions best when it receives nutrition spread throughout the day. Aim to drink your PKU protein substitute 3-4 times evenly spaced throughout the day.
  • Have trouble remembering to take your protein substitute? Set an alarm on your phone to remind you to take your PKU protein substitute throughout the day.
  • Consider a diet journal so that you can keep track of your intake throughout the day.

"Spreading my PKU protein substitute intake throughout the day helps stop me from being hungry and overeating other foods." 


Plan ahead

  • If you use a powdered protein substitute, you can mix your protein substitute in advance. Most PKU protein substitutes can be refrigerated for up to 24 hours after mixing. Just remember to shake before you drink!
  • Request a Lophlex Cool Bag to keep your protein substitute cool or a beaker to mix it in on the go.
  • Speak to your dietitian if you would like to try a ready-to-drink PKU protein substitute to save time.

Start the day off right

  • Breakfast is still the most important meal of the day so be sure to have a serving of your PKU protein substitute in the morning.
  • If you use a powdered protein substitute, mix your PKU protein substitute the night before and refrigerate it overnight, if mornings tend to be hectic.
  • You can blend in fresh or frozen berries to make a smoothie.

"I like to drink PKU Lophlex® LQ at work because it is very easy and convenient which fits well with my busy schedule."


Don’t leave home without it

  • Pre-measure the powder the evening before and add water or a flavoured drink when you are ready to have your PKU drink; or speak to your dietitian about using a product in prepacked pouches.

  • TIP: Use a clean, re-usable container that is not see-through if you don’t want others to know what you are drinking. Request our reusable pouches if using a powdered protein substitute.

Don’t leave home without it

  • Keep backup PKU protein substitute in a convenient place to use as needed in case you forget or leave home without it.


  • In your bag or purse
  • In your desk drawer at work
  • At your friend’s house
  • In your personal locker

"My protein substitute is no different than the guys drinking protein shakes each morning at the gym. Mine is just a protein shake for PKU."


Be creative

  • Make a smoothie by adding ice cubes or frozen fruit to your protein substitute in a blender.
  • Freeze your PKU protein substitute for 1-2 hours and eat it with a spoon.
  • Mix protein substitute into a cold store bought beverage while on the go.

"I love being creative with my PKU protein substitute. I mix it all different ways so I don’t get tired of it."


Don’t run out

  • Keep track of how much PKU protein substitute you have at home so you can pick up or order more from your pharmacy or via the home delivery service (if applicable) advance.
  • If possible, make a standing order with your pharmacy or home delivery provider (if applicable), so you get a shipment every month and never run out.
  • Leave yourself at least a 2-week supply of protein substitute; just in case there is a delay in your delivery.

"Remember, one day at a time. Returning to the PKU diet is a journey, not short term sprint."


Taking the next step – as easy as 1-2-3

How we can help you

  • Learn more about returning to diet and advances in PKU products.
  • Check out our ‘products page’ to learn about our product range and hear more from others on a low protein diet in the ‘your stories’ section.
  • With the help of your dietitian, find a PKU protein substitute that matches your personal needs.
  • Connect or re-connect with a metabolic healthcare professional. Use our metabolic centre map to find your closest metabolic centre.

Start making the PKU diet part of your daily

  • Set a plan for preparing low protein meals. See our low protein meal planner for inspiration.
  • Hit the market and stock up on fresh fruits and vegetables.
  • Make a plan and set specific times for drinking your protein substitute.

Stay in tune with how you are feeling

  • Talk openly with friends and family.
  • Ask if they see improvements in you and/or your behaviour whilst returning to diet.
  • Set small goals, like staying on diet for a full day, then a week, then a month.
  • Celebrate you and your success.

Share your story and help others like you get back on the PKU diet

"Returning to the PKU diet was the best thing I ever did for myself and my family."

David, age 40

"Whether you were told to go off-diet as a child or just took yourself off-diet as a teen, it is never too late to go back on diet. Getting my PHE-levels back in control was the hardest and BEST thing I have ever done."

Katie, age 31

NOTE: The information provided on this page is for guidance purposes only and is in no way intended to replace the care, advice and medical supervision of your healthcare professional. If you have any questions about the information provided here, please speak to your doctor or dietitian.