Food is a subject that fascinates more and more French people. And for good reason. Eating is an act of connection between our environment and our body and it is obvious that our state of health is influenced by our diet. Its role in health has grown even more since studies on the intestinal microbiota – intestinal flora -, that is to say the bacteria present by the millions in our digestive tract and which are capable of modulating our immune system. .
However, the effects of diet on the intestinal microbiota are difficult to determine precisely due to significant variability in the composition of the intestinal flora between individuals, largely linked to each person’s genetic heritage. It is estimated that among the 160 species making up the microbiota, only half is found from one individual to another, or a variability of 50%. For comparison, the interindividual variability of the genome – all of human genes – is of the order of 0.1%.
Gluten-free to fight rheumatoid arthritis?
Like any food, gluten – a set of proteins found in many cereals such as wheat, barley, rye – influences our microbiota. Many foods contain it: bread, pasta, semolina, sausage. And according to some, a diet banning all foods containing gluten would restore “protective intestinal flora”. However, celiac disease must be differentiated from gluten intolerance. In celiac disease, which is an autoimmune disease, the immune system reacts to gluten causing sometimes serious digestive problems. The concept of gluten intolerance, which is a different entity from celiac disease, has only appeared in recent years. It manifests itself by digestive disorders, such as bloating or constipation. Symptoms that could be alleviated by limiting the consumption of certain sugars – Fodmaps – containing in particular gluten.
Despite the absence of celiac disease or gluten intolerance, many people have chosen to no longer consume gluten, due to certain beliefs conveyed on social networks, or by certain media. This movement is currently booming in Western countries, as evidenced by the 34% increase in the sale of gluten-free foods in the United States between 2009 and 2014. In France, it is estimated that currently nearly 10% of the population no longer consumes gluten. Obviously, since gluten is seen by the general public as a “bad food”, patients suffering from rheumatism experiment with food, most often without talking to their doctor. One of the most common practices is to follow a gluten-free diet… Some patients report a reduction in their pain, others not. But ultimately what does science say?
Rheumatoid arthritis is the most common chronic inflammatory rheumatism. This autoimmune disease causes, in the absence of appropriate treatments, inflammation in the joints, a source of pain, disability and sometimes irreversible joint deformation. It is the consequence of the association of several factors such as genetic predisposition, smoking or obesity. Despite everything, the origin of the onset of the disease is not perfectly understood. Some scientific studies have revealed that a disruption of the intestinal microbiota could occur during the development of early rheumatoid arthritis.
“The scientific evidence supporting the benefit of a gluten-free diet in the treatment of polyarthritis is non-existent.”
Through its influence on the composition of the microbiota, gluten could therefore play a role in the triggering and progression of this rheumatism. This is why more and more patients are turning to a change in their lifestyle, and therefore their diet, in the hope of being able to improve their pain, sometimes to the detriment of taking proven medications. However, the scientific evidence underlying the benefit of a gluten-free diet in the treatment of polyarthritis is theoretical, but not demonstrated in humans.
Two imperfect studies that demonstrate nothing
Only two studies, of questionable quality, studied different diets including the gluten-free one. In the first clinical trial published in 1991, the authors evaluated the effect of a dietary modification, including a gluten-free diet, in around fifty patients. After more than a year of follow-up, these subjects certainly had a little less pain, but the authors failed to specify the treatments associated with the diet. It cannot therefore be ruled out that the improvement in pain is simply the effect of drug treatment such as anti-inflammatories or corticosteroids, for example. However, the latter are very effective in polyarthritis, although they cause undesirable effects which should make their use sparing. The second trial compared the effect of a vegan diet combined with a gluten-free diet to a normal diet. At the end of this study, which lasted one year, people who stopped eating gluten had less pain, but saw the appearance of irreversible joint deformities.
It is important to emphasize that in these two studies, patients who removed gluten from their diet lost significant weight. However, it has been shown that weight loss reduces the severity of rheumatoid arthritis. The improvement in pain could therefore be the direct consequence of the weight loss and not of the diet which allowed this weight loss. Finally, in these two studies, almost half of the participants did not complete the study, thus skewing the conclusions – what the researchers call attrition bias.
Against rheumatoid arthritis, weight loss
Experts from the French Society of Rheumatology have established recommendations, in 2022, concerning the diet of patients suffering from inflammatory rheumatism. They emphasize that since the gluten-free diet has not been proven, it cannot treat rheumatoid arthritis and therefore cannot replace drug treatments. However, it must be recognized that we need further studies. Which is good, since a randomized controlled trial is underway in France. It should also be remembered that the gluten-free diet can be harmful, costs more than a traditional diet and can be responsible for social isolation. It has also been suggested in some studies that a gluten-free diet is linked to increased cardiovascular risk. And we should also not forget the fashion effect of the gluten-free diet, which it is very likely that players in the food industry are riding on by investing massively in the development and promotion of gluten-free foods. While the scientific evidence is non-existent!
On the other hand, even if the effect of the gluten-free diet remains to be determined, several studies have proven the benefits of a quality diet on the progression of rheumatoid arthritis, particularly through weight loss. Obesity is currently a public health problem in France and around the world. Nearly one in two French people are overweightwhose deleterious effect is well known both on the cardiovascular level (risk of myocardial infarction, stroke, etc.), oncological (risk of breast and colon cancer), metabolic (risk of diabetes) , psychiatric (risk of depression), as well as chronic inflammatory rheumatism. Several clinical trials have shown that overweight patients have more severe forms of rheumatoid arthritis..
Aside from the beneficial effects of weight loss, it is interesting to note that the Mediterranean diet – poor in sugars, salts and red meats, but rich in fruits, vegetables, fish and legumes -, without stopping the evolution of rheumatoid arthritis, would reduce the pain. Five scientific studies also suggest the effectiveness of the Mediterranean diet on rheumatoid arthritis pain.
Having joint pain is already difficult to live with: it impacts quality of life, increases fatigue and makes you depressed. It is therefore useless to add to these sufferings a deprivation of gluten for an uncertain expected benefit at the cost of significant sacrifices. The most important thing seems to be to follow the National Nutrition and Health Program (PNNS), which promotes a varied and balanced diet and helps combat excess weight. Sometimes it is the simplest advice that is most helpful, more so than punitive exclusion regimes.
* Jordane Saunier is a rheumatologist in Lyon, Prof. Jérémie SELLAM is a rheumatologist at Saint-Antoine hospital (AP-HP) and professor at Sorbonne Universities.
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