Sensitivity to gluten influenced by negative expectation

Complaints due to gluten sensitivity are partly related to people's expectations. Celiac disease and wheat allergy have been ruled out as causes in these people. Recent research from the universities of Maastricht and Leeds shows that the expectation that gluten causes gastrointestinal complaints plays a crucial role in whether or not people experience these complaints. This points to a direct involvement of the brain-gut interaction, the so-called brain-gut axis, in experiencing symptoms after gluten intake. Relatively little is still known about this. The study results were published on 29 November in the scientific journal The Lancet Gastroenterology and Hepatology.

Gluten

Increasingly, people are reducing their gluten intake because of self-reported digestive symptoms, despite the fact that celiac disease and wheat allergy have been ruled out. The origin of their symptoms is often not clear. Therefore, the Dutch and English scientists wanted to investigate the effects of consumer expectations on complaints after gluten intake. More than 80 subjects with self-reported gluten sensitivity participated in the study and were divided into four groups. The results of the psychological study left nothing to be desired: people who thought they were being fed gluten did report complaints, and people who thought they were being fed something without gluten reported significantly fewer complaints.

In reality, half of each group did get to eat gluten and the other half ate gluten-free. In all participating groups, it was found that people's expectations play a prominent role in whether or not they report symptoms. "We see in our study a so-called nocebo effect when eating gluten," says researcher Marlijne de Graaf. "Based on the negative effects that people expect after eating gluten, they experience symptoms even if it turns out afterwards that they did not actually eat gluten. So although the cause is partly 'between the ears', that does not mean that the complaints are not real."

Brain-gut axis

Indeed, the results of this study suggest a clear involvement of the brain-gut interaction in gluten sensitivity. Relatively little is still known about this. The researchers therefore now want to focus on unravelling these kinds of mechanisms in the brain-gut axis. "Due to the influence of interactions between the brain and the intestines, people can really experience abdominal pain, a bloated stomach or diarrhoea, for example, after eating gluten," says Daisy Jonkers, professor of intestinal health at Maastricht University. "But the cause of these symptoms is not only due to eating gluten, so a gluten-free diet is not the only solution."

To treat this problem, the scientists want to investigate further the influence of the brain on the development of intestinal complaints. "For example, we want to know exactly which areas of the brain are involved," Jonkers says. "But we also want to know which substances play a role in the communication between the brain and the intestines, and whether people might react differently to this. Moreover, it is quite possible that some people cannot tolerate wheat products well because of substances in wheat other than gluten. And that therefore there is indeed something in wheat that can lead to, for example, stimulation of the immune system or excessive production of gas by the intestinal flora. We also want to investigate that further."

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