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'When we tried to explain PKU to people in the past, they'd say we were mad, things are different now'

People with this rare genetic condition need to maintain strict low-protein diets.

PHENYLKETONURIA (PKU) IS a rare genetic disorder that affects a person’s metabolism.

People with the condition need to maintain highly regimented low-protein diets, with 95% of “normal” food off-limits.

Newborns in Ireland are screened for the condition via the heel-prick test. The country has one of the highest rates of PKU in Europe. 

About one in every 4,500 babies here is diagnosed with PKU or a milder form of the condition, compared to one in every 12,000 babies in the UK.

PKU-Food-pyramid Source: PKU Ireland

If untreated, PKU can result in permanent brain damage and other serious health issues. However, a person can live a relatively normal life once the condition is monitored and they follow a strict, sometimes expensive, diet. 

An average adult diet includes about 70-80g of protein per day. For someone on a PKU-approved diet this can drop to as low as 4g daily (the equivalent of one small potato).

Sarah Tierney (41), from Naul in Dublin, was diagnosed with PKU as a newborn. She has “classic” PKU, meaning she can consume about 7g or units of protein a day. Some people with the condition can consume up to 20 units per day. 

For example, a potato, packet of crisps or six chips would be the equivalent of one unit of protein, and a shop-bought vegetable burger could be four to five units.

Growing up in the ’80s 

Sarah can’t eat most meat or dairy products, often opting for meals that include salad or vegetables, potatoes or a waffle, or PKU-friendly sausages and pasta. She takes a blood test once a month to make sure her condition is under control.

Her sister Jenny was also diagnosed with PKU as a baby and she said being able to talk to each other about the condition when growing up was a big help as most people didn’t understand what it was.

IMG_0161 Sarah and her mother Liz. Source: Sarah Tierney

Having two children with PKU required “an awful lot of forward planning from my mother, she was always baking us food – back in the ’80s that was the only way, she had to prepare a lot of our meals from scratch”.

It was the late ’70s when we were diagnosed, my mother had never heard of it. When she tried to explain it to people, they’d say ‘you’re mad’. Things are different now. 

“Sometimes we’d say we were vegetarian as that was easier to understand, but then you’d have to explain to people that dairy products were also a no-no.”

Sarah said she was “very self-conscious” about having the condition when she was a teeanger but now feels much more in control of it.

She said the growing number of people choosing vegetarianism and veganism has resulted in people generally being more accepting and aware of others’ dietary wishes and needs, something that wasn’t always the case in the past.

There are a lot more food options available to people with PKU nowadays, but basic items like bread and pasta are more expensive than their standard equivalent.

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IMG_4492 Sarah with her husband Lee and daughter Emily. Source: Sarah Tierney

“Living with PKU requires a lot of preparation and forward-planning. It really is a diet for life,” Sarah said.

If she were to eat more protein that she should, the side-effects would not be immediate but she would start to feel them over time. 

If I was to eat more protein than I should, while I wouldn’t see the effects immediately, after a while I would begin to experience symptoms of anxiety and loss of concentration.

In general, children with PKU who eat too much protein experience worse symptoms as their brains are still forming. The PKU Association of Ireland has been campaigning for children with the condition to be granted access to Kuvan, a medication that could improve their quality of life. 

Sarah’s six-year-old daughter Emily was screened for PKU but doesn’t have the condition.

Sarah said her condition requires a lot of meal-planning but noted that “very few genetic conditions have such a positive outcome, saying: “Once you have a diagnosis you can follow the diet, take your supplements and live life to your full potential.”

PKU will be one of the conditions discussed at a conference to mark the 12th annual World Rare Disease Day this week. Bridging Health & Social Care, organised by Rare Diseases Ireland, is due to take place on Thursday, 28 February, in Dublin city. People who wish to attend can register here

About the author:

Órla Ryan

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