SONIA 2 – Controlling Protein to Support Nitisinone Treatment
In today’s blog Chief investigator Prof. Ranganath reinforces the need for SONIA 2 patients taking nitisinone to keep on top of a controlled protein Diet.
Why is a controlled protein diet important for those taking nitisinone?
Dietary protein is made up of building blocks. One such building block is called tyrosine. In most western diets, there is too much tyrosine due to consuming a lot of protein. Most of the tyrosine is surplus to requirements and is degraded further. After nitisinone, this excess tyrosine cannot be degraded and accumulates. This can lead to high blood tyrosine levels. Very high tyrosine levels can lead to eye and skin problems. Cutting down on protein intake in those taking nitisinone helps to maintain lower tyrosine levels. This can help patients safely stay on nitisinone.
What are the risks if not followed?
Very high tyrosine levels can lead to eye and skin problems. The eye problems are usually symptomatic leading to symptoms like redness of the eye, tearing of the eyes, blurred vision or eye pain. However, sometimes eye problems may be present with minimal symptoms. Therefore, if you experience any eye symptom, get your eyes checked by an eye specialist (slit lamp examination). Some patients may experience allergy or eczema like skin reaction. Stopping nitisinone temporarily (4 - 8 weeks) will be enough for the eye and skin symptoms to clear up.
What foods/diet should be followed?
As part of participating in the SONIA 2 study, you were provided with a diet sheet. (Below) The diet sheet gives information on those foods that are higher in tyrosine. Avoiding tyrosine-rich foods is sensible. In addition, eating slightly less protein can also help to maintain lower blood tyrosine levels.
If you have symptoms in the eyes or skin, please contact your own GP immediately. You should also contact the staff at your trial site immediately. Please contact the AKU Society who will support and help you to find a solution to your problem quickly.
You have been given an alert card with names and telephone numbers in case of emergency.
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Controlling Protein to Support Nitisinone Treatment in AKU
Why Control Protein?
Nitisinone causes blood tyrosine levels to rise. Tyrosine is an amino acid found in protein. It also comes from the breakdown of another amino acid called phenylalanine.
Controlling the amount of protein in your diet may therefore help prevent the tyrosine level rising too high. High levels can cause damaging side effects that would mean stopping nitisinone treatment.
If you follow any dietary restrictions already you are advised to access specialist dietetic advice to ensure your diet remains nutritionally adequate.
Eating food containing protein
Most of your protein should come from: meat, meat products, fish, pulses (meat substitutes) and dairy products. You are advised to have no more than 90g cooked weight of meat or fish at your main meal & 60g for your snack meal.
- Oily fish is recommended twice a week for heart and joint health.
- Eat 3 dairy food portions per day to ensure you have enough calcium.
Other foods that contain protein and so will count towards your daily protein intake include: potatoes and starches, seeds, cereals and all nuts. You are advised to have 5 – 6 portions of these foods every day.
Eating food that doesn’t contain protein
Foods that contain little or no protein can be eaten freely. These comprise: fruit, vegetables, fats, sugar, and flavourings. Bananas contain some protein, so it is advised to eat only one per day. All drinks, including soft drinks and alcohol can be consumed freely. However you should avoid foods and drinks containing aspartame (an artificial sweetener).
Aspartame is an artificial sweetener derived from phenylalanine, so is not advised when taking nitisinone. It is used in a wide range of ‘diet’ and ‘low sugar’ products, such as: yoghurts, some biscuits and desserts, crisps & alcoholic drinks. All products containing aspartame (E951) should contain the following warning ‘contains a source of phenylalanine’.
- All other sweeteners are suitable such as Sucralase & Saccharin.
Reading food labels
Packaged foods and meals will all provide nutritional information on their labels to allow an estimation of the protein content. Read food labels carefully to avoid those with high protein. It may be displayed as “per portion / meal” or “per 100g of product”.
Weigh yourself regularly alongside blood monitoring. If you start to lose too much weight, contact the clinical trial centre as your intake may have become too low.
Aim for a daily protein intake of 0.8 g per Kg body weight. For example, if your weight is 70 Kg, then you should consume no more than 56 g of protein per day