Gluten sensitivity

Bread, brain and bowels

Our daily bread is increasingly considered problematic. Gluten sensitivity is a complex phenomenon and while there’s nothing wrong with avoiding gluten, it is a serious restriction and not always necessary. Daisy Jonkers and Marlijne de Graaf researched the effect of expecting to consume gluten – with rather comforting results.

Professor of Intestinal Health Daisy Jonkers researches the relation between food and gastrointestinal diseases such as Irritable Bowel Syndrome (IBS), which affects 5-10% of the general population. It’s a functional disease without a single clear organic cause and is diagnosed based on symptoms. “It’s still often considered a taboo topic for patients. It is currently defined as a disorder of the brain-gut interaction, associated with many factors such as altered motility, disturbed microbiome, low grade inflammation, leaky gut, anxiety, depression and so on.”

IBS has a complex aetiology and presents heterogeneously, so it’s difficult to unravel the multifactorial web of causes and effects. “Together with our European partners, we are building a cohort of 600 patients whom we’ll test extensively to identify which factors contribute.” While not life-threatening, “it’s a burden for the patients and their quality of life is sometimes as bad as those of patients with a clear organic disease, such as diabetes. It can be very painful and it can seriously restrict your ability to participate in a lot of activities conducive to your wellbeing.”

According to Jonkers, people often indicate that certain foods trigger symptoms of the condition. While gluten sensitivity is certainly not the same as IBS, wheat products are often singled out as culprits with reference to the gluten they contain – also in the absence of celiac disease. Jonkers and her PhD candidate Marlijne de Graaf, a dietician and nutritional scientist, wanted to see if that causality can be substantiated with a view to figuring out the mechanism.

G(l)uten Appetit

Gluten is a protein present in grains such as wheat, barley or rye. It adds elasticity to the dough and allows the resulting product to rise during baking. The more gluten, the higher the potential fluffiness [technical term] of the bread. “Any product that contains wheat also contains gluten, from bread to pasta, pizza, cookies and everything else made from wheat,” explains De Graaf and is quick to specify that “unless you have celiac disease, an autoimmune disease that causes intestinal damage, we don’t think consuming gluten in itself is a bad thing.”

Worrying about gluten might have adverse effects though. Non-celiac gluten sensitivity has no biomarkers and is diagnosed by scoring gastrointestinal symptoms after gluten intake and withdrawal after celiac disease and wheat allergy has been ruled. Common symptoms include a gastrointestinal distress in all its forms as well as headaches, fatigue, respiratory issues, depression and many more.

Jonkers and De Graaf wanted to figure out if and to what extent the nocebo effect might play a role. Nocebo, the opposite of the more well-known placebo effect, describes patients’ expectations causing them to experience negative effects. Of course, they first made sure to medically rule out anyone with celiac disease and wheat allergies, to avoid causing participants harm.

Working with a European consortium of research institutes and bread manufacturers, their study revolves around naturally gluten-free (and reportedly delicious) oat bread, to which just gluten – not wheat – could be added. The test sites were in Maastricht, Wageningen and Leeds. The non-celiac gluten sensitive participants filled in a baseline questionnaire to assess their symptoms and then had to keep score of their symptoms on an hourly basis and in the days to follow.

Read more about the study on gluten sensitivity and expectations in this press release.

Worrying about gluten worse than eating it

The participants were divided into two groups: one expected to consume gluten; one did not. Those two groups were both divided, unbeknownst to them, once more into two groups: those who had gluten added to their oat bread and those who did not. “The groups that didn’t expect to have gluten had the least symptoms, whether they had actually consumed it or not,” De Graaf summarises. “The group that expected gluten and received it had the most symptoms. The group expecting gluten but not getting it was in the middle.”

Some people report that they tolerate spelt better than wheat. While the two grains have measurably different gluten contents, the absolute differences are very small and may not be clinically relevant. Additionally, De Graaf points out that the composition of grains can vary even more between climates and soils than between grain types. Jonkers adds that, while the method of preparation for sourdough bread does break down more gluten than the method using yeast, the majority of gluten remains intact, also in sourdough bread.

No panacea - relax and eat healthy

Jonkers points out that the different bread types are biochemically quite similar. “It indicates that the mechanism might be a lot more complicated than previously thought. In practice, it means that people who react badly to one type of bread could still try out other types to see whether they can digest it better.” De Graaf adds that the first study only investigated the effects of gluten but that other components of the grains, such as amylase-trypsin inhibitors or fructans, might also trigger symptoms.

While unlikely to trend anytime soon, the conclusion is that nutrition and gastrointestinal health is dauntingly complex – certainly more complex than pointing to a single ingredient as the culprit. So is gluten good or evil? “We can’t rule out that gluten may have had an additional effect in our study but the nocebo effect was very evident.” Jonkers is agnostic on the matter; her main concern is that people follow a healthy, varied diet. “If you avoid wholegrain bread you might lose out on a lot of vitamins, minerals, fibre and phytochemicals, so that’s worth keeping in mind.”

De Graaf thinks it’s problematic that social media have a tremendous reach and impact people’s dietary habits, often without scientific evidence supporting their claims. Jonkers adds: “We want to give good, nuanced and safe advice. Follow a well-balanced diet with a wide variety of food, not too high in calories and saturated fat, lots of fibre and plant-based proteins…” She suggests people listen to their body and keep in mind that digestive health is about more than food. Anxiety causes gastrointestinal distress in many people – as has been borne out by both studies.

Text: Florian Raith

marlijne de graaf

Marlijne de Graaf is a PhD Candidate at NUTRIM (School of Nutrition and Translational Research in Metabolism). She holds an MSc Nutrition and Health and a BSc Nutrition and Dietetics.

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