Issue 130 pku diet challenge

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PKU DIET CHALLENGE Lisa Gaff Registered Dietitian, Addenbrooke’s Hospital, Cambridge

Lisa and Nicole are both fairly new to the area of Metabolics, so they decided that one of the best ways to truly appreciate what they ask of patients and their families would be to follow a PKU diet for a week. Here they report on how they fared by adapting meals, cooking with the low protein alternatives and attempting to take the required volume of protein substitute.

Lisa works with adult patients with diabetes, severe insulin resistance and metabolic conditions.

Phenylketonuria (PKU) is a rare inherited metabolic condition where patients are unable to metabolise phenylalanine, one of the 20 amino acids found in protein. Without strict dietary treatment, phenylalanine builds up in the blood stream which can lead to severe neurological impairment in children.

People with PKU can usually tolerate small amounts of natural protein depending on their age, genotype and residual enzyme activity.

This natural protein is prescribed as an exact number of 1g protein (50mg phenylalanine) exchanges which need to be evenly distributed throughout the day. This protein allowance is reviewed regularly, based on the monitoring of the phenylalanine levels. To replace the protein, a phenylalanine-free amino acid mix needs to be taken to provide enough of the remaining amino acids to meet their protein requirement.

During childhood, while the brain is developing, the PKU diet needs to be followed strictly. Whilst, previously, adults have been given the option to come off the diet once brain development is complete, more recent evidence shows that concentration, emotional wellbeing and cognitive ability can be affected by high phenylalanine levels.

It is now recommended that the diet is continued for life.1 Foods, such as meat, fish, eggs, cheese and nuts (high in protein and, therefore, high in phenylalanine)

Nicole Mills Registered Dietitian, Addenbrooke’s Hospital, Cambridge Nicole is a Paediatric Dietitian working with ketogenic, metabolic and surgical patients.

and foods containing the artificial sweetener aspartame (which contains phenylalanine), must be avoided. Some foods, such as potato, cereals and certain vegetables, contain enough protein to require counting as exchanges, whereas most fruits, vegetables and salads can be eaten in normal quantities. There is an expanding number of low protein alternatives available on prescription, such as bread, biscuits, flour, pasta and cake mixes.

THE CHALLENGE

By taking the challenge through adapting meals, cooking with low protein alternatives and attempting to take the required volume of protein substitute for a week, we felt we would be better placed to support and advise patients with PKU and their families.

Most of our patients have a daily natural protein restriction of between 5-12g, therefore, we set ourselves an 8g allowance (2g breakfast, 3g lunch and 3g dinner) with three protein substitutes a day to meet our protein requirements (~1g/kg/day). We started with a good selection of low protein products, protein substitutes and lots of recipes and ideas. After removing any temptations from our houses and stocking up with lots of low protein and unrestricted foods, we were ready to begin our PKU challenge.

TAKING THE PROTEIN SUBSTITUTES

Taking sufficient amino acid substitute is something patients report as challenging

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. . . armed with a burger mix, low protein burger buns and a sausage mix, I was ready to embrace the PKU experience.

. . . vegan mozzarella, olives and roasted vegetables as protein-free foods and had a rocket and spinach salad, low protein burger bun and sausage and burger substitutes to provide the remaining protein. due to the distinct tastes and inconvenience.

There are a broad variety of phenylalaninefree protein substitutes available in the UK which range from pre-made drinks, powdered supplements, dessert style supplements and the new GMP (glycomacropeptide) products, but often patients will choose one type and not deviate.

Nicole: On day one, I selected a powderbased product as my first protein substitute and had the (not so) bright idea of making it a longer drink to dilute the taste, a choice I soon regretted having extended the drink to last a lengthy and somewhat gruelling 10 minutes. Throughout the week, I tried a range of different preparations and was able to settle on a liquid-based substitute which was much more palatable and by mid-week, the protein substitutes became less of a burden and more of an appetiser.

Lisa: Similar to Nicole’s experience, I initially found the amino acid substitutes quite challenging to take and it also took me a few tries to find options that I could tolerate, but again, towards the end of the week, I found that I was almost enjoying these. The variety of protein substitutes available now is far wider than previously and something patients returning to diet comment on. Unlike Nicole, I liked the taste of powders best (which demonstrates it is important to offer full choice of options to patients, as we all have different taste buds), but as these were not as convenient as pre-made, I was taking a combination of these through the week.

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WHAT ABOUT OUR PROTEIN EXCHANGES?

We had both expected the trickiest part of the diet to be restricting the amount of protein in meals. In reality, it was much easier to choose protein-free options rather than keep to an exact amount of protein containing foods that suited the meal.

On the first day, we both opted for low protein toast with butter (protein-free) for breakfast; this actually tasted quite similar to regular bread and was quite pleasant, although we hadn’t appreciated how tricky it would be to find breakfast-worthy items with exactly 2g of protein. After searching our respective fridges and cupboards, we settled on rice cakes (Nicole) and tinned sweetcorn (Lisa) - not your usual breakfast choices, but it was our first learning point. After re-thinking breakfast, we settled on a more sensible plan for a weighed amount of yoghurt to meet our 2g protein breakfast allowance.

Throughout the week, meal preparation and planning became easier. Lunches were a mixture of roasted low protein vegetables with spinach and rocket as exchanges (25g spinach = 1g protein), or low protein baguettes (available on prescription) with protein-free cheese. Evening meals varied from low protein pasta with pesto and roasted vegetables, to butternut squash with ratatouille and low protein cheese. We were both impressed by the variety of exchange-free vegan cheeses available in the supermarkets (information that will become handy within the PKU patient group, but also when supporting families using milk-free diets). There were also some products that contained significantly less protein than expected: some jars of readymade

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On the menu was a roasted vegetable pasta dish which was listed as freshly made to order . . .

. . . I took a box of low protein pasta and asked the chefs whether they could use it with their sauce which they were happy to do so. white sauce contain ~1g protein per 100g, surprisingly little considering the homemade equivalent would usually be made with cows’ milk and cheese.

We both found ourselves relying heavily on pre-portioned foods to top up our exchanges to the required amount at each mealtime. Rice cakes featured in most meals (conveniently providing 1g protein per rice cake), to the extent that we would both be happy not to see another rice cake in quite some time.

HOW DID WE COPE WITH EATING OUT ON A LOW PROTEIN DIET?

Nicole: On the first day on the diet, I went to a family barbecue (not an easy event to start a low protein diet!), but armed with a burger mix, low protein burger buns and a sausage mix, I was ready to embrace the PKU experience. Mistake one was to completely under-season the burgers: as well as containing little protein, they also seemed to have very little flavour. Luckily, I could make a second attempt and they improved dramatically. I’d used vegan mozzarella, olives and roasted vegetables as protein-free foods and had a rocket and spinach salad, low protein burger bun and sausage and burger substitutes to provide the remaining protein. Overall the meal was great and everyone was keen to try the low protein alternatives (perhaps photographing the burgers next to the ‘real thing’ was slightly unfair!).

Midweek, we had our annual summer work social: a pizza buffet followed by punting and games on the river. As one of the organisers, I was perfectly positioned to ensure that the buffet catered for our PKU diet. I had been

enjoying the challenge of rethinking regular food/snack choices to fit in with the diet, until I stood surrounded by 15 freshly cooked pizzas covered in normal protein-containing cheese what an exercise of self-control! We made our PKU-friendly pizzas from low protein pizza bases, tomato puree, free-from mozzarella, topped with roasted vegetables. The first attempt wasn’t particularly successful as the cooking time for the pizza bases transpired to be roughly half the time for the free-from cheese to melt, resulting in an eye-wateringly crunchy base, burnt tomato and undercooked cheese.

By attempt three, the pizza was mastered and impressed the majority of the team. Finishing with Lisa’s handmade low protein lemon cupcakes for dessert, the buffet was a big success.

Having forgotten to consider drinks, we quickly realised that the majority of the drinks were sugar-free, therefore, aspartamecontaining. Luckily, there was one bottle of sugary lemonade - so we were still able to enjoy a Pimms.

Lisa: I had a couple of dinners out during the week and also enjoyed the summer social as Nicole has mentioned. My first dinner out on day one was a semi-successful experience. On the menu was a roasted vegetable pasta dish which was listed as freshly made to order and so I took a box of low protein pasta and asked the chefs whether they could use it with their sauce which they were happy to do so. They seemed interested in the diet and didn’t make this feel like an awkward request. Unfortunately, however, when the dish arrived, the top had

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IMD WATCH been sprinkled with cheese! I scraped this off, but it did demonstrate very well the pitfalls when people don’t understand the diet.

As this pasta dish was yet another exchangefree option, I was able to treat myself to a small amount of chips for my exchanges. My other meal out was less successful, as there wasn’t anything on the menu (not even any salads) that seemed appropriate and so I ended up just eating sweet potato fries.

WHAT HAVE WE LEARNT?

Nicole: During the week, my self-control was regularly exercised, particularly when colleagues brought in sweet treats from their holidays abroad or birthday cake. For me, this was a week on a tightly-controlled diet; for children with PKU, this is their everyday reality.

It must take a huge amount of commitment and outstanding parenting skills to keep to exact protein exchanges every day.

At times, I found devising and cooking meals based on my preferences quite challenging, but for parents, this must be so much harder, as children’s likes and dislikes can change frequently. For parents making meals for both unrestricted diets and PKU diets simultaneously, it must be particularly challenging to ensure that their children’s meals are appealing, palatable and also to ensure that their children don’t feel as though they are missing out on other foods that siblings without PKU can enjoy freely.

Lisa: I was interested as to whether I would be hungry on the diet as this is something patients can report. I didn’t find increased hunger, but I also think I took the term ‘free’ foods literally and found myself snacking a lot of the day on ‘free’ biscuits, crackers and cakes, which I wouldn’t normally do. While the low protein products tasted different to their counterparts, I feel that I would easily get used to these, especially if used to the diet from birth. I think the main difficulty if I were to have to follow this long term would be to not be able to share the diet with my family, as unlike some other diets such as gluten- and dairy-free, it would be unsafe for family members to share the low protein diet.

We have both significantly improved our awareness of the PKU product base and naturally low protein options. This will particularly help us to support parents wanting to increase the variety in their children’s diets and adults considering returning to a PKU diet. We found a lot of useful options in the ‘free-from’ product ranges: wheat- and dairy-free products are often low in protein, therefore, the experience has improved our knowledge of the dairy- and wheat-free market which will help when giving parents and patients practical suggestions on different types of restricted diet.

We both felt that the week was a really useful way to gain insight into the diet and practicalities of living with PKU and would encourage anyone working with metabolic patients to give it a go.

Thanks to Mevalia, Nutricia, Promin, Taranis and Vitaflo for supplying a generous selection of their amino acid substitute products and low protein food products for this PKU challenge.

Reference 1 Wegburd et al (2017). The complete European guidelines on phenylketonuria: diagnosis and treatment. Online at: https://ojrd.biomedcentral.com/ articles/10.1186/s13023-017-0685-2

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