Gluten is not welcome? No, clearly, for some of the people who decided to oust it from their plate. What do they blame him for? To cause bloating, spasms and transit disorders, but also headaches, fatigue, itching, joint pain ...
Described for the first time in 1978, what is known today as non-celiac gluten sensitivity (SGNC) has been the subject of scientific consensus for several years. "Doctors define it as a clinical entity in which the ingestion of gluten causes digestive and extra-digestive symptoms which regress under a gluten-free diet, explains Catherine Grand-Ravel, researcher at INRA. But it is not based on autoimmune mechanisms like in celiac disease, nor on allergic mechanisms like in wheat allergy. Symptoms to describe it but no diagnostic tool: what is this sensitivity? If eating gluten-free is vital for celiac patients, what about when you don't have this disease?
Is a gluten-free diet more digestible?
It's possible. "Gluten proteins are rich in proline, an amino acid that makes them less accessible than others to enzymes in the digestive tract," says Dr. Nadine Cerf-Bensussan, director of research at Inserm. As a result, gluten digestion leaves small fragments. "In celiac patients and in people allergic to wheat, some of these fragments can be recognized by the immune system and trigger their disease," she said.
In people with non-celiac gluten sensitivity, an effect on intestinal permeability has been reported. "The submucosa is particularly innervated, this permeability can generate symptoms such as bloating or diarrhea," says Prof Bruno Bonaz, gastroenterologist. However, without anyone knowing why, this does not concern everyone. "One of the tracks explored is the interindividual difference in perception of sensations: interoception or awareness of the internal state of one's body," continues Professor Bonaz. Presumably, the nerve signals sent from the gut to the brain may be amplified in some people. It could often be people who are stressed, anxious, or depressed.
In the absence of characteristic markers such as in celiac disease or wheat allergy, only the exclusion of gluten can determine if the digestive difficulties are related to its ingestion. And again: not for sure.
"When we remove foods containing gluten, we also remove other substances such as FODMAPs, especially fructans, which can also cause intestinal fermentations and inflammation of the digestive tract, notes Prof Christophe Cellier, gastroenterologist. It is still difficult to identify the culprits. But gluten is not the only cause. "
Does it reduce inflammatory bowel disease?
No, with the exception of celiac disease. "It is only in celiac patients that the ingestion of gluten causes an inflammatory reaction, easily detectable by blood markers, recalls Professor Cellier. This damages the intestinal wall and destroys the villi: this is what necessitates the complete ousting of the foods that contain it. "
For other inflammatory bowel diseases or irritable bowel syndrome, gluten is not involved and does not worsen inflammation. "On the other hand, one can think that its eviction makes it possible to alleviate the symptoms, insofar as it is badly digested by some", estimates Bruno Bonaz. The American Rheumatology Association recommends a gluten-free diet during flare-ups. Thus, people suffering from inflammatory digestive diseases say that they feel better without gluten.
Are joint or rheumatic disorders improved?
Yes, in some. Again, no causal link, no scientific evidence, but testimonials. "It is believed that gluten could increase the inflammatory state in these patients by increasing intestinal permeability," suggests Bruno Bonaz. But without proof. "
Does it have an impact on diabetes?
Not at all, or indirectly. "It is only in celiac disease that there is a link between gluten and type 1 diabetes," says Christophe Cellier. In both cases, autoimmune diseases. As for the effect that a gluten-free diet can have on type 2 diabetes, it depends mainly on the food hygiene adopted. "If it is a question of replacing wheat and its derivatives by industrial products like bread, pizzas, cookies ... gluten-free, the effect is rather harmful because these products are often enriched with sugar and fats and the flours used have a high glycemic index, ”notes Cédric Ménard, dietitian. "If, on the contrary, eliminating gluten means eating healthier by reducing the share of industrial products and increasing the share of fresh, naturally gluten-free products such as fruits and vegetables, meats, fish ... impact on health parameters can be positive, ”adds Dr. Nadine Cerf-Bensussan.
Does it help you lose weight?
Sometimes. Again, it all depends on what the gluten-free diet is made of. If, by eliminating the foods that contain it, you reduce your consumption of industrial products, this can lead to a decrease in energy intake. "If, on the other hand, we do not change the way we eat and we just trade gluten products for gluten-free products, the effect could on the contrary be negative," suggests Nadine Cerf-Bensussan . "Gluten does not make you fat or lose weight," says Christophe Cellier.
Are we fitter, less tired?
Perhaps. But this effect is then indirect. "We are looking for a placebo effect," says Professor Cellier. When you change your diet, and you are sure you are doing yourself good, it can generate a certain dynamism. The easier the digestion, the lighter and fitter you feel. What about athletes who claim to see their results increased tenfold with a gluten-free diet? "A study has been conducted in the United States on this subject among cyclists," notes the gastroenterologist. They were blindly put on gluten-free and gluten-free diets. Conclusion: there is no difference in performance. "
Professor Bonaz’s opinion is less clear cut: "It is possible that by modifying the permeability of the intestinal wall, gluten succeeds in crossing the intestinal barrier and is found in circulation in the blood. This could act at the level of the cerebral barrier (blood-brain) or at the level of the vagus nerve, and thus generate fatigue, headaches ... But these are only hypotheses. "
Are allergies reduced?
No. With the exception of wheat allergy and celiac disease in which the ingestion of gluten results in an inappropriate reaction of the body's immune system, gluten does not generate allergic reactions. "Again, the improvement described by some may be indirect," says Professor Bonaz. When we digest better, we are less stressed, which can reduce allergic reactions. We must not dismiss the track of relations between the brain and the digestive tract. "
Does the gluten-free diet have a positive impact on mood and cognitive abilities?
Apparently, in some. Several hypotheses have been put forward: the placebo effect, the relationships between the intestines and the brain, the composition of the microbiota. “A growing body of data shows that it can influence behavior and sensitivity to stress, underlines Nadine Cerf-Bensussan. The consumption of gluten could perhaps modulate the composition of the intestinal flora. However, nothing has been demonstrated. "
What conclusions?
There is a sensitivity to non-celiac gluten which manifests itself in digestive and extra-digestive symptoms which arise after ingesting it, and disappear when it is ousted. But "there is no objective criterion to establish a diagnosis," said Professor Cellier.
Unlike celiac disease and wheat allergy, this sensitivity is not serious. "Excluding gluten improves the discomfort felt, but it is possible for these people to consume it without consequences for their health," notes Bruno Bonaz.
If there is, for the moment, no scientific explanation, several hypotheses are put forward, such as the links between the brain and the intestines or the microbiota. The problem may not be limited to gluten. "Some specialists speak rather of a sensitivity to wheat, notes Bruno Bonaz. It is, in fact, important to take into account the other components of food implicated in the symptoms experienced (FODMAPs). "
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