Living with Phenylketonuria (PKU) and a Protein Restricted Diet in Ireland

Ever wondered why a customer …..asks you to heat a pale looking bread roll or pizza base? Asks for the protein ingredient list? Requests that you cook their pasta or milk alternative? Enquires which vegetables come with your vegan option? Weighs their food after being served? Uses a blue 50ml scoop to serve their food? Asks for water to make up a supplement at their meal? ..….they may be managing a low protein diet.

Once administered in the first two weeks of life, low protein dietary therapy prevents profound intellectual and physical disability for those adhering to it, and has been in place in Ireland since the introduction of newborn screening in 1966. Therefore the oldest Irish patients adhering to the recommended ‘diet for life’ who do not have an intellectual and physical disability are approximately 53 years of age. Ireland has one of the highest incidences of PKU in the world with 1:4,500 born with PKU compared with 1:10,000 worldwide. This rare metabolic condition affects a person’s ability to breakdown an amino acid in protein called phenylalanine. If phenylalanine builds up in the blood stream it can cross the blood-brain barrier and can cause brain damage. As well as those with PKU, patients with other metabolic conditions such as HCU, MSUD, GA1 and Tyrosinemia also adhere to low protein dietary therapy and yet no one seems to have heard of it!

What is low protein dietary therapy? Approximately 85% of regular foods are off limits. The diet itself is complex for those managing it as it consists of a daily allowance of 1) natural protein often as little as 2-8g per day (referred to as exchanges), 2) protein free foods predominantly fruits, vegetables and medical foods and 3) a synthetic protein supplement taken at regular intervals throughout the day. The introduction of the sugar tax has led to food manufacturers replacing sugar with a cheaper alternative ‘Aspartame’ a source of phenylalanine and toxin to the brain for those with PKU. Research suggests that 70% of adolescents and 60% of adults with PKU do not consistently adhere to the diet as they find it too difficult. Many studies have confirmed that eating out can be challenging for those with PKU and often leads to mismanagement of the diet and social isolation as many social gatherings include food. Professor Anita MacDonald, a consultant dietitian, of the Scientific Advisory Committee of the European Society for PKU and Metabolic Disorders has highlighted that protein labelling is often inaccurate or misleading and poses a further threat for those with PKU

What would happen if someone with PKU ate the wrong food? As it is an intolerance rather than an allergy, the impact of over exchanging is not immediate. The customer may develop symptoms such as a headache and some adults claim that their heads may feel “a little fuzzy”. Reverting to the diet alleviates these symptoms. If however they continued to mismanage diet it would have serious neurological implications particularly for children and adolescents as their brains are still developing.

How can chefs accommodate low protein dietary therapy? Chefs when informed comment that a low protein diet can be easily accommodated in a restaurant setting as there is no risk of cross contamination and the customer will always be well informed on dietary management and this can naturally alleviate any concerns the chef may have. The customer too takes responsibility for measurement once the appropriate foods are available to them.

The following food items as outlined by the National Centre for Inherited Metabolic Disorders are allowed freely in the diet:

Protein free vegetables: Artichokes, Asparagus, Aubergine, Beansprouts, Beetroot, Butternut, squash, Cabbage, Capers, Carrots, Cassava, Celeriac, Celery, Chayote, Courgette, Cucumber, Curly kale, Fennel, French beans, Garlic, Gherkin, Green beans, Leeks, Lettuce, Mangetout, Okra, Onions, Pak choi, Parsnips, Peppers, Pumpkin, Radish, Rocket, Runner beans, Samphire, Scallions, Shallots, Spring onion, Sugar snap, peas, Swede, Tomato, Turnip, and Water chestnuts.

Protein free fruits: Apple, Apricots, Blackberries, Blackcurrants, Blueberries, Cherries, Clementine, Cranberries, Currants, Damsons, Dates, Dragon Fruit, Figs, Ginger, Gooseberries, Grapefruit, Grapes, Guava, Jackfruit, Kiwi, Kumquat, Lemons, Limes, Lychees, Mandarins, Mangoes, Mangosteens, Melon –cantaloupe, Melon –honeydew, Nectarines, Olives, Papaya, Passionfruit, Peaches, Pears, Physalis, Pineapple, Plums, Prunes, Raisins, Raspberries, Rhubarb, Satsumas, Star fruit, Strawberries, Sultanas, Tangerines and  Watermelon.

Seasonings: Chilli, Curry paste, Curry powder, French dressing, Herbs, Mint sauce and jelly, Mustard, Pepper, Salt, Spices and Vinegar.

Miscellaneous: Baking powder, Bicarbonate of soda, Buttercream icing, Cornflour**, Cream of tartar, Pasta, noodles or rice made from konjac (Asian root vegetable) Sprinkles, Some custard powders**, Sago** and Tapioca**.

Food essences and colourings: Almond essence, Cochineal, Peppermint and Vanilla.

Fats and oils: Butter, Coconut oil, Duck Fat, Fry light spray, Grapeseed oil, Garlic oil, Goose fat, Lard, Margarine, Olive oil, Rapeseed oil, Sunflower oil, Sesame oil, Vegetable oil.

Drinks: Some coconut milks, Hemp milk, Minerals*, Pure fruit juice, Rice milk (not suitable in children under 5 years or pregnant/ lactating women) Squashes/cordial* Tea/coffee/herbal tea served with milk alternative, Water/ soda water/mineral water.

Sauces*: Apple sauce, Balsamic vinegar, Brown sauce, Cranberry sauce, Chutney, Horseradish sauce, Ketchup, Most mayonnaises, salad creams, Mustard, some pasta sauces, Piri Piri sauce, Relish, Salad dressing, Soya sauce* Sweet chilli sauce, Tomato salsa, Tabasco sauce.

Foods normally considered ‘carbohydrate based’ such as bread, cakes and pasta are considered significantly high protein sources in a low protein diet and are therefore not permitted. In addition to protein free foods used for their calorific value, the customer may select a low protein option from your menu to meet their daily protein allowance, the quantity of which is based upon their blood phenylalanine levels. Examples of one gram servings of protein include: 1.5 x 50ml scoop of mashed potato, 2 tablespoons of peas, 1 x 50ml scoop of sweetcorn, 1 x 50ml scoop of boiled rice, 1 tablespoon of baked beans and 1 tablespoon of chickpeas. For larger scale events the customer can provide the chef with flour, milk, pasta, bread, rice alternatives as well as easy to follow menu options.

*Aspartame (E951/E962) is not permitted in the diet. **Protein free desserts and puddings must be reconstituted with protein free milk alternatives provided by the customer.

For further information please see or or alternatively you can email the PKU Association of Ireland at Please follow the PKU Association of Ireland on twitter @pku_ireland to assist us in creating awareness amongst the food industry.

Low Protein Cooking resources: and

Bernadette Gilroy PKU Association of Ireland and TJ O Connor Senior Lecturer Hotel, Culinary Arts and Tourism Institute of Technology Tralee