Thousands of people across Wales could be living with an undiagnosed autoimmune condition because they are dismissing symptoms such as tiredness and brain fog as part of everyday life, according to new research released for International Coeliac Awareness Day.

New figures from Coeliac UK show that 27 per cent of adults in Wales would not speak to their GP about symptoms linked to coeliac disease, despite the condition affecting around one in every 100 people in the UK.

The charity says awareness of the condition remains “worryingly low”, with many people overlooking symptoms that could point to a serious long-term health problem.

Research commissioned by the charity found that 43 per cent of people in Wales dismiss persistent tiredness as normal, while 30 per cent say the same about brain fog or difficulty concentrating – both recognised symptoms of coeliac disease.

Coeliac disease is an autoimmune condition in which the body attacks its own tissues when gluten is consumed, damaging the lining of the gut and preventing nutrients from being properly absorbed. Gluten is found in wheat, barley and rye.

Although digestive issues such as bloating and diarrhoea are more commonly associated with the disease, the charity says symptoms can affect the whole body, including fatigue, anaemia and neurological problems.

The survey also found that nearly half of UK adults who are aware of coeliac disease do not realise it can cause symptoms beyond digestion. Many people instead blamed stress, ageing or lifestyle factors for symptoms rather than a medical condition.

According to Coeliac UK, only 36 per cent of people with coeliac disease in the UK have been formally diagnosed, with an estimated half a million people still undiagnosed. Adults wait an average of 13 years from the onset of symptoms before receiving a diagnosis.

Untreated coeliac disease can lead to serious complications including osteoporosis, infertility, chronic gut ulcers, neurological damage and an increased risk of infections.

Hilary Croft, Chief Executive of Coeliac UK, said: “This isn’t a lifestyle choice or a popular food trend – it’s a serious autoimmune condition.

“We’re seeing people normalise symptoms and ignore their body’s warning signs. Signs that could point to coeliac disease.

“The result is that many people end up waiting for over a decade before they find out what’s causing their pain and discomfort. Fatigue, brain fog or ongoing digestive issues shouldn’t just be dismissed as part of a busy life or getting older.”

Former Olympic swimmer Rebecca Adlington has backed the awareness campaign after being diagnosed with coeliac disease at the age of 35 during investigations into recurring miscarriages.

She said the diagnosis “completely changed” her life and explained years of symptoms she had not previously understood.

“Within just a few months of cutting gluten out completely, I felt like a different person,” she said.

“There’s still so much more awareness and understanding needed, which is why campaigns like this are so important and why people need to spot the signs and get tested.”

Racing driver Flame Airikkala, 19, has also joined the campaign, saying she hopes sharing her experiences will help educate more people about symptoms, diagnosis and living with the condition.

Coeliac UK is encouraging people experiencing persistent or recurring symptoms to seek medical advice and use its online self-assessment tool to help identify whether they could be at risk.