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Breakthrough Tribunal ruling: PKU diet a ‘therapy’ for Personal Independence Payments

A Tribunal has held that the dietary treatment for patients with phenylketonuria is a therapy for the purposes of Personal Independence Payments (PIP).

Phenylketonuria (PKU) is a rare metabolic condition that affects the body’s ability to digest phenylalanine, an amino acid contained in protein. If undigested, this amino acid is extremely toxic to the brain. This means patients with PKU must severely limit their protein intake, otherwise they will be brain damaged.

About 6,000 people in England have PKU. They are prescribed strict dietary treatment from birth.

Foods which are protein-rich (such as meat, fish and cheese) and flour-based foods like bread, pastry, and cakes must be completely cut out. Most other foods can only be eaten in very small quantities, so these must be carefully calculated and the portions weighed out. To get enough nutrition, patients also have to take amino acid supplements and include special low-protein prescription foods in their meals.

Managing this treatment is extremely complicated. Every meal, snack or drink must be carefully planned in advance and takes a long time to prepare. NHS England estimate that patients with PKU and their families spend on average 19 hours per week managing their diet1.

Personal Independence Payment (PIP) is a disability benefit for people aged 16-65 paid by the Department for Work and Pensions (DWP). PIP is assessed based on how much help a person needs with ordinary daily living activities (like cooking or washing) and their mobility.

One of the key ‘daily living activities’ is managing therapy or monitoring a health condition.

However the DWP has not routinely accepted that the PKU diet is a therapy. This means people with PKU are often denied the ‘daily living activities’ component of PIP, even though many patients need several hours of help from relatives each week to manage their diet.

In a significant development, however, a Tribunal have now decided that the PKU diet qualifies as a therapy, following a legal challenge brought by a 21 year old man with PKU. The DWP had refused his application for PIP so he appealed to the First Tier Tribunal.

The 21 year old’s case was originally heard by the First Tier Tribunal in 2018 but they, like the DWP, considered that his PKU dietary regimen was not a ‘therapy’. This meant they found he did not meet enough of the criteria in the PIP Regulations to qualify for PIP.

The Claimant appealed to the Upper Tribunal, which said the First Tier Tribunal had not given adequate reasons for their decisions and should look at the case again.

At this point the 21 year old and his mother approached Hayley Chapman, Trainee Solicitor at Hodge Jones & Allen. Hayley represented the Claimant at the new hearing in March 2020. It was argued the PKU dietary treatment meets the relevant definition of a therapy under the PIP Regulations and that this is supported by an array of medical literature. Evidence was also submitted about the help the young man needed with this therapy and other activities of daily living.

The Tribunal decided that the PKU diet was a therapy under the PIP criteria. It also decided that the 21 year old needed help with his therapy, and accepted this took more than 14 hours per week. This meant he met the criteria to qualify for PIP. He will now receive £87.65 a week plus a back payment in excess of £12,500.

Hayley Chapman said: “Since the strict and time-consuming PKU dietary regime is the only treatment routinely available for PKU on the NHS, and the consequences of getting it wrong are so dire for patients, it was not right that the DWP did not see it as a therapy. It was a further injustice that this way of defining the diet was a barrier to people with PKU qualifying for disability benefit. We are pleased that the Tribunal have recognised that the PKU diet is a therapy and that as a result our client qualified for PIP. I hope this ruling will make a difference not only to our client but to many other people with PKU in the UK.”

Kate Learoyd of the National Society for Phenylketonuria (NSPKU) said: “This is amazing news which could have a great impact on the PKU community. Thank you so much for your hard work and dedication; this judgment will hopefully change many lives.”

For further information on PKU and dietary management, and for guidance on how to apply for PIP if you have PKU, please contact the NSPKU via their website.


1)  NHS England ‘Clinical Commissioning Policy: Sapropterin for Phenylketonuria (all ages)’, published 21 December 2018  p.7 

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