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Phenylalanine Explained

By Dietitian, Juliette Kellow BSc RD

Q: I’ve noticed the warning ‘Contains a source of phenylalanine’ on many low-calorie drinks and yoghurts. I’ve heard this chemical can be dangerous. Is it better to consume drinks with sugar rather than those with these substitutes?

A: Phenylalanine is something of a mystery to most people and many of us think it could be a health risk because, as you say, it’s frequently labelled on low-calorie products. However, rather than being a dangerous chemical, phenylalanine is actually an essential amino acid (a building block for protein), which can’t be made by the body and needs to be supplied in the diet. This amino acid is actually found in many foods including meat, fish, milk, eggs and cheese with the result that most of us have large amounts in our daily diet.

However, phenylalanine is also one of the main ingredients in the artificial sweetener, aspartame. Also given the more-friendly name Nutrasweet, Canderel is one of the most popular aspartame-based sweeteners in the UK.

In the past, there have been many health scares about the risk of aspartame. However, more than 200 objective scientific studies have shown aspartame to be completely safe. As a result, it’s safety has been confirmed by the regulatory authorities in more than 100 countries including the European Commission’s Scientific Committee for Food, America’s Food and Drug Administration and by experts within the United Nation’s Food and Agriculture Organisation and the World Health Organisation.

Hearing all this, you might then wonder why products containing aspartame are labelled as containing phenylalanine! It’s basically because people born with a rare genetic disorder called phenylketonuria are unable to properly metabolise phenylalanine and so have to limit intakes of all foods that contain this amino acid, including meat, fish, dairy, eggs and products containing artificial sweeteners. In America, the warning on labels is slightly clearer and says: ‘Phenylketonurics: contains phenylalanine”. It’s also worth pointing out that children or adults can’t suddenly develop phenylketonuria – it’s a condition you’re born with – so there’s no reason to concern yourself with whether or not a food contains this amino acid.

In answer to your question about finding substitutes to foods that contain aspartame as a sweetener, the choice really is yours. There’s certainly no health risk attached to consuming them, but some people find low-calorie or sugar-free products less satisfying than the real thing. If this is the case for you, you might prefer to choose naturally sweet foods or have smaller amounts of the real thing. Bear in mind, for example, that one level teaspoon of sugar contains just 17 calories so if you only have one coffee a day with sugar, it’s hardly going to ruin your diet. However, it’s also worth remembering that eating foods containing artificial sweeteners will do little to curb a sweet tooth in the long run, so rather than relying on them heavily, it might be better to try and gradually wean yourself off them slowly.

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