What is celiac disease?

Some people avoid gluten because they believe it is healthier. Others are severely affected by celiac disease and experience a marked improvement once they are diagnosed and change their diet. And then there is a large group who have the condition without knowing it - because they have very few symptoms.

Celiac disease is a common chronic condition - and at the same time one of the most overlooked. The disease occurs when the body reacts to gluten, a protein found in wheat, rye and barley, among other grains. Around 1 per cent of the population has celiac disease, and prevalence may be even higher in some northern European countries. Many people go for years without receiving a diagnosis.

One reason is that the symptoms can vary greatly - from classic digestive problems to more diffuse signs such as fatigue, iron deficiency or headaches. In some people, the disease is only discovered late, once it has already led to deficiencies such as osteoporosis.

Professor Steffen Husby from the Department of Clinical Research, who has researched celiac disease for many years, has written a review article in the New England Journal of Medicine together with a colleague, summarising the latest knowledge about the disease. We asked him to explain what happens in the body, how the disease is diagnosed - and why a gluten-free diet is still the only treatment.

What is celiac disease — and how does it differ from gluten intolerance, gluten allergy and wheat allergy?

Celiac disease is a condition in which the body reacts to gluten. Gluten is a protein found in wheat, rye and barley. It is what is known as an autoimmune disease, where the immune system attacks the body itself, and the reaction primarily takes place in the small intestine. Celiac disease can also be referred to as gluten intolerance, but celiac disease is the correct term to use.

The condition affects around 1 per cent of the population, and the figure is higher in the Nordic countries. Many people go for years without being diagnosed because the symptoms vary greatly and some are very diffuse. There is also a very large group who have no symptoms at all.

To develop celiac disease, a person must both be genetically predisposed and consume gluten. The condition can develop at any age - from childhood to adulthood.

Is celiac disease the same as gluten allergy?

No. Gluten allergy is something different. It is an allergic reaction typically seen in bakers, who are exposed to dust from flour and gluten-containing products.

What happens in the body in celiac disease?

When people with celiac disease eat gluten, it triggers an immune reaction in the intestine. This leads to inflammation in the gut and damages the tiny folds in the intestinal lining that normally help the body absorb nutrients.

As a result, the body has greater difficulty absorbing iron, vitamins and calcium, among other nutrients, which may cause changes in bowel habits, weight loss and, in children, impaired growth.

But the disease is not only about the gut. It can also affect other parts of the body and may, for example, cause non-infectious liver inflammation, joint and muscle pain, affect the nervous system or lead to dermatitis herpetiformis - a very itchy skin rash associated with celiac disease.

Does it get worse over time or the more gluten you eat?

There is no clear relationship between symptoms, disease duration and the amount of gluten in the diet.

Why is celiac disease so difficult to detect?

The symptoms of celiac disease vary greatly. Some people have no symptoms at all, which can make the disease very difficult to detect.

In most cases, the disease process begins in childhood, but celiac disease can develop at any stage of life.

We still do not know exactly what causes the disease to develop. Genetics and gluten are necessary prerequisites, but infections, gut microbiota, environmental toxins and early dietary habits may also play a role.

Because the disease affects the intestine, the classic symptoms of celiac disease are digestive. These include bloating, abdominal pain, diarrhoea and weight loss. However, there may also be more diffuse signs, such as fatigue, mouth ulcers or headaches.

Some people have no obvious digestive symptoms at all, and more than half of Danish patients with celiac disease have no symptoms.

What does the disease course look like in children and adults?

In children, a typical disease course may involve impaired growth, diarrhoea or constipation. This is often picked up by the doctor during routine child health examinations, and the diagnosis is then made.

In adults, celiac disease is often only discovered because of deficiency conditions such as calcium deficiency, or entirely by chance during other medical examinations. For example, this may happen if a person undergoes an endoscopy because of suspected cancer or as part of screening for celiac disease.

There is not necessarily a link between how damaged the intestine is and how many symptoms a person has. This means the disease can remain active for many years without being detected.

How is celiac disease diagnosed today?

Diagnosis is based on a blood test measuring - in medical terminology - IgA antibodies against tissue transglutaminase (tTG-IgA). A tissue sample from the small intestine is then taken.

If tTG-IgA levels are very high, children and younger adults may not need a tissue sample. Instead, an additional blood test for celiac disease, the so-called EMA test (endomysial antibody IgA), can be performed.

Should you eat gluten before a celiac disease test?

Yes - and this is very important. You need to eat gluten before the test; otherwise the disease can be difficult to detect. If you suspect you may have celiac disease, speak to your doctor before starting a gluten-free diet. Otherwise, blood tests and tissue samples may give misleading results.

How is celiac disease treated - and is medication on the way?

The only documented treatment is a lifelong gluten-free diet. Even small amounts of gluten can keep the disease active, so treatment requires careful attention in everyday life. In most people, symptoms improve once gluten is completely removed from the diet, and the body can gradually heal.

Celiac disease cannot be cured, but if it is detected and treated, people can live without symptoms and avoid long-term complications. Even if symptoms disappear on a gluten-free diet, the body will still react to gluten, which is why the diet must be maintained for life.

Can you get medication for celiac disease?

New treatments are currently being researched, but there is still no medication that can replace a gluten-free diet. Clinical trials involving medical treatment are ongoing, but so far none have proven effective.

Fortunately, we have become much better at diagnosing the disease and understanding how it affects the body. This means we can detect celiac disease earlier and help more people live symptom-free lives. It has also become easier to live with celiac disease because the range of gluten-free products available in supermarkets has expanded significantly in recent years.