Gluten is a type of protein. It gives dough made from gluten-containing cereals its elasticity. When people with coeliac disease eat foods that contain gluten, the body creates antibodies just as it does with an allergy. However, these antibodies target not only the protein itself but also the body’s own structures, similarly to an autoimmune disease. For this reason, coeliac disease is not an allergy in the stricter sense, even if both involve the immune system.
Gluten is found in wheat, rye, barley and other types of cereal grains. The disease causes inflammatory changes in the small intestine that make it more difficult for essential nutrients to be absorbed. Secondary diseases may also occur that affect overall health or other organs in the body.
Prevalence in children and adults
For many years, it had been thought that the coeliac disease emerges in childhood. However, we now know that it can occur at any age. The prevalence of the disease is approximately the same in both children and adults, but women have it more often than men.
Specific tests in Europe have revealed that around 1% of the entire population in Europe and North America suffer from coeliac disease. In a health study conducted on over 12,000 children and adolescents in Germany, blood tests revealed the presence of coeliac disease in around 0.9% of participants.
The exact cause of coeliac disease is unclear. It probably differs from patient to patient and is likely due to a number of different factors. Since coeliac disease often runs in families, researchers assume that genetic predisposition plays an important role. In addition to people whose immediate family members have coeliac disease, people with Down syndrome (also called trisomy 21) are another risk group, as are people with type 1 diabetes or other diseases. It is unclear whether infant nutrition is a factor in the development of the disease. However, experts recommend feeding newborn infants small amounts of gluten while continuing to breastfeed them during this adaptation period.
The symptoms of coeliac disease are triggered by gluten-containing foods such as bread, bread rolls, cakes, pasta or muesli. Research has shown that many adults do not show symptoms after consuming very small amounts of gluten (less than 10 milligrams per day), but others experience symptoms after consuming very small amounts below this level.
The disease causes a very broad range of symptoms. Patients may suffer from digestive disorders such as diarrhoea, constipation, bloating, vomiting, chronic abdominal pain or loss of appetite. But they may also show signs of poor overall health or other symptoms. These may include fatigue, anaemia, pallor, weakness, osteoporosis, or increased sensitivity to pain. However, there are also many patients who have tested positive for the disease in blood tests yet have only extremely mild symptoms or none at all.
In coeliac disease, inflammatory reactions cause the intestinal villi to become smaller over time. Since the body absorbs essential nutrients and fluids via the intestinal villi, deficiencies occur over time due to the decreased surface area.
From a medical standpoint, coeliac disease is different from other diseases such as wheat allergy. The symptoms of wheat allergy and the treatment options can be similar to those for coeliac disease and must therefore be considered when making the diagnosis.
Similar gastrointestinal symptoms such as those of a wheat allergy can also cause what is referred to as non-coeliac wheat sensitivity. The symptoms of this condition have not yet been clearly defined. It is unclear whether it is the gluten or other components in wheat that trigger the reaction. Individuals with wheat sensitivity experience abdominal pain, bloating, and in some cases diarrhoea; they also report tiredness, headaches and muscle/joint symptoms. Wheat sensitivity is determined through a diagnosis of exclusion: If the examination results are negative for allergies and coeliac disease, and the symptoms disappear with a gluten-free diet, the patient may have wheat sensitivity. However, it is still widely debated within the medical community as to whether non-coeliac wheat sensitivity actually exists.
If coeliac disease is suspected, the doctor asks the patient about his or her eating habits, symptoms and family history (anamnesis). The diagnosis is confirmed if specific antibodies are found in the blood that are reduced with a gluten-free diet and additionally if certain tissue changes in the intestine can be identified. The antibodies are usually what are called transglutaminase IgA antibodies, which are found at higher levels in nearly all coeliac disease patients. Some patients are generally deficient in this type of antibody (immunoglobulin A [IgA] deficiency), which can mask coeliac disease; therefore this is also tested. The patient should also be tested for nutrient deficiencies, for example, vitamin B12, iron, folic acid or calcium.
In addition to laboratory tests, an examination of the digestive tract (endoscopy) is performed to confirm the diagnosis. In this procedure, a thin tube with a camera on the end is used to view the inside of the small intestine. At the same time, small tissue samples (biopsy) can be taken that are later analysed under a microscope.
If coeliac disease is suspected, it is important for the patient to consume gluten-containing foods on a regular basis for at least two to three months before these examinations. If the patient has completely eliminated gluten before the tests, coeliac disease usually cannot be confirmed.
It can be difficult for doctors to recognise coeliac disease in adults without specific reasons to suspect it because the symptoms are often atypical or less pronounced than in children. Adults may also have lower levels of antibodies (antibody titres) and only very slight changes to the intestinal tissues.
There is currently no effective treatment for the causes of coeliac disease. Therefore the only available treatment is a lifelong gluten-free diet. However, patients should not change their diet until they have received the diagnosis and the doctor has recommended it. The switch to a gluten-free diet should be supervised by a qualified nutritionist in order to ensure a well-balanced diet.
Individuals with coeliac disease also have an increased risk of developing other serious conditions such as diabetes or cancer. For most of these diseases, the risk can be reduced by following a gluten-free diet. This is why medical associations recommend that symptom-free patients with a confirmed diagnosis also follow a gluten-free diet or at least understand the advantages of such dietary changes.
Living with coeliac disease
Since gluten is in found in so many foods, it takes a lot of knowledge and discipline to follow a completely gluten-free diet. Gluten occurs naturally in wheat, spelt, rye, barley, freekeh, einkorn, emmer and kamut, but is also found in all foods that are made from them, e.g. flour, starch, semolina, pearl barley, flakes, breadcrumbs and pasta. Therefore gluten is also found in all regular breads, bread rolls, cakes, cereal bars, snacks, pasta, coatings, etc. But it is also hidden in many foods that one might not initially suspect, for instance, products made of potatoes, fruit or milk, flavoured drinks, spices, sauces, sausages and processed meats. In addition, gluten-free foods can be contaminated by residues from gluten-containing foods. For this reason, people with coeliac disease should also use gluten-free appliances – for instance, a toaster for toasting gluten-free bread only.
The German Coeliac Society DZG ( www.dzg-online.de) provides comprehensive information on coeliac disease and gluten-free diets; it also has a food list for patients, families and the general public. In addition, it offers many helpful tips on going out to eat, travelling, gluten-free recipes, the coeliac passport and much more.
In Europe, all processed foods that are available through at retail sales points must be labelled. Products with a Crossed Grain symbol or ‘gluten-free’ label on the package are considered safe. But beware: gluten-free processed foods are not always healthy, since they often contain added sugar and fat in order to improve their taste and consistency.
Just as other patients with chronic conditions, people with coeliac disease should see their doctor regularly. DZG recommends that patients visit their doctors three, six and twelve months after starting a gluten-free diet and once a year thereafter.
Prof. Dr. med. Dr. h.c. T. Zuberbier
Last changes made: July 2016
Felber J et al. S2k-Leitlinie Zöliakie, Weizenallergie und Weizensensitivität. Hrsg. Deutsche Gesellschaft für Gastroenterologie, Verdauungs- und Stoffwechselkrankheiten (DGVS), 2014. Leitlinie gültig bis April 2019.