After the ingestion of gluten-containing foods (e.g. wheat, rye, barley) or drinks, some people suffer those symptoms similar to that associated with a gluten intolerance (coeliac disease); these include abdominal pain, bloating or diarrhoea as well as other symptoms such as bone and joint pain, muscle cramps, weight loss, skin rashes, headaches, depression or chronic fatigue. In this case, the presence of coeliac disease (usually by a blood test and/or gastroscopy with tissue samples taken from the small intestine) and a wheat allergy (determination of IgE antibodies and allergy testing by a skin prick test) should be excluded.
After this exclusion process, a 6- to 12-month gluten-free diet can be undertaken, whereby the symptoms usually improve within a few days or no longer occur. To confirm the diagnosis, it can be discussed whether the re-introduction of gluten to observe the potential recurrence of symptoms should be considered. Should this be the case, NCGS can be regarded as probable.
We highly recommend against implementing a gluten-free diet without prior tests, since the diagnosis of coeliac disease is then often made impossible (i.e. the increased blood values of, for example, tissue transglutaminase IgA normalise in coeliac patients on a gluten-free diet after about 3 - 6 months with alterations in the small intestine after 6 - 12 months).
Also, there are large overlapping with, for example, irritable bowel syndrome. Patients with irritable bowel symptoms also often experience an improvement in their symptoms with a gluten-free diet.
The existence of a NCGS diagnosis is under doubt by some research groups. The improvement of gastrointestinal complaints under a gluten-free diet may also be explained by reducing dietary FODMAPs (i.e. foods which can trigger bloating in the gastrointestinal tract, see FODMAP section).
In all cases, a gastroenterological evaluation should be considered before making any dietary changes, and further therapy should be made under the guidance of nutritional counselling.