What Factors Affect Phe Levels

As with the rest of the adult population, eating a healthy varied diet, enjoying good quality sleep and staying physically active, all have a part to play in this. However, if you have PKU, an additional consideration is keeping your Phenylalanine (phe) levels within the levels recommended for you.

Knowing what can affect your phe levels can help you understand how to cope with levels if they increase. Some of the factors that might affect your phe levels include:

• Being unwell.
• Physical activity and undereating.
• Rapid weight loss.
• Hormonal changes e.g. the menstrual cycle and early stages of pregnancy.
• Eating more or less phe exchanges than advised and not taking your protein substitute as prescribed.

Your metabolic team will be able to give you more guidance on these, so you will know what to expect.

It is important that you contact your metabolic team or GP if you are unwell and struggling to eat and drink enough.

If you must take medication when unwell, remember, some medications contain aspartame, which is a source of phe, and these must be avoided (unless your doctor or metabolic team tells you otherwise). Always check the ingredients of medications with your metabolic team or pharmacist before taking.

Here are some suggestions on how to minimise the rise in your phe levels during illness:

• Try and eat small frequent meals as tolerated to ensure adequate energy (calorie) intake.
• Aim to take your protein substitute as normal. If you’re unable to do so, make sure you contact your metabolic team straight away.
• Consider your phe exchanges. Your metabolic team may advise you to cut back on phe exchanges if phe levels are raised. You might find that this will have happened naturally as appetite may be reduced during illness.
• Stay hydrated. Ensure adequate fluids are taken especially if your symptoms include vomiting and/or diarrhoea.
• Check for suitable medication. Look out for aspartame and seek the guidance of your pharmacist or metabolic team if you’re unsure. It is also important not to mix any medications through the protein substitute as this will alter the taste and consistency.

It is important that exercise is not forgotten as you become more socially busy and your life may change to working, often involving full time hours or shift work, moving out of home and taking control of your PKU diet, including your own cooking and shopping. Adjusting to these huge life changes will often mean that there is less time, and exercise is often forgotten.   

Many adults in Australia follow an inactive lifestyle. Research suggests that 39% of adults are failing to reach the governments recommendations of 150 minutes of exercise a week. A sedentary lifestyle is linked to obesity, heart disease and type 2 diabetes. Your current routine of tertiary study or your job may require you to sit for many hours a day.  A sedentary lifestyle can be harmful to your health, so physical activity is encouraged wherever possible and for all ages.  

There are many benefits of exercise one being that regular exercise (or manual labour) builds muscle mass and means your body will use protein to build this muscle. Phe, as an amino acid, is a building block of protein so, the phe from your diet will be used to help build muscle.

For more information on PKU and exercise see Physical Activity and Exercise. 

It is helpful to keep a count of the protein you eat and monitor your blood phe levels to ensure you are getting the right amount of natural protein. Your dietitian can help teach you about protein in foods, meal planning and counting protein.

Undereating protein can cause phe levels to drop too low. Phe is an essential amino acid so it is important you eat enough to meet your body’s needs, but not too much that your levels are high. It is a fine balancing act. If your phe levels are too low your dietitian will ask you to increase your intake of natural protein.

As the diet for PKU is so restrictive in natural protein quantity and quality it does not provide sufficient amino acids and vitamins and minerals to meet your body’s requirements. The protein substitute supplements your diet to ensure your body obtains the nutrients it requires.

Without it you are at risk of deficiency and your body will break down your muscle stores releasing phe into your blood, causing levels to be high. Consuming the right amount of protein substitute over the day to meet your requirements is best to keep your phe levels within the normal range. Speak to your dietitian if you are having trouble consuming the amount you need or simply would like an alternate option. There are many to choose from, so there may be a better option for you.