2024-01-16 18:26:20
Western diets can have deleterious effects on the microbiota, with the resulting dysbiosis being a factor promoting inflammation and immune disorders. The nutritional approach is an attractive idea to help patients control their disease. Rheumatologist Alexandra Albert (Neuville, Quebec) presented the scientific foundations and the resulting practical perspectives during the 36th Congress of the French Society of Rheumatology (9-12 December 2023, Paris). If the theory is attractive, clinical evidence remains to be collected.
Microbiota and rheumatological diseases
We know the role of the microbiota in digestion, but we also know its importance for the immune system and its action. A healthy microbiota produces more than 800 bacterial metabolites which interact with the body, the immune system, which, if they are not all characterized, participate in the local balance. In case of dysbiosis, LPS (lipopolysaccharides), exogenous nucleic acids or toxins can cross the intestinal barrier, with immunological risks and formation of autoantibodies. In practice, intestinal dysbiosis is found in many rheumatological diseases: ankylosing spondylitis, osteoarthritis, lupus, Sjögren’s, psoriatic arthritis, fibromyalgia, rheumatoid arthritis (RA), and these abnormalities appear before the disease itself. It induces clonal lymphocytic inflammation and the production of autoantibodies. For example, in rheumatoid arthritis, we observe an increased prevalence of Prevotella capri in 70% of cases. These bacteria, when introduced into mice, promote the appearance of the disease. And the more severe the dysbiosis, the more serious the disease. In HLA B27+ ankylosing spondylitis, the severity of dysbiosis is also associated with the severity of the disease, as well as intestinal cell death, promoting permeability and passage of LPS. Some studies suggest that dysbiosis causes ankylosing spondylitis, not the other way around.
The weight of the diet
Metabolism plays a role in this equation, since leptin levels, modified for example in obesity, modulate both innate and adaptive immunity, and can thus influence inflammation and autoimmune diseases. Studies have described the influence of leptin levels on the pathophysiology of osteoarthritis or RA. Finally, it should be remembered that the inflammatory markers linked to obesity (CRP, TNF alpha, IL-6) are common to those involved in pain. In terms of food, intestinal permeability is increased by gluten gliadin. Zonulin, from cell junctions, is a marker of intestinal permeability: several studies describe an increase in its level in inflammatory rheumatological diseases, sometimes even before symptoms according to certain studies. This has been confirmed by others who describe the presence of intestinal bacterial markers in synovial biopsies of patients with osteoarthritis or RA.
An unbalanced diet primarily leads to an absence or deficiency of cofactors important for immunity (zinc, magnesium, etc.). Some of these foods are also pro-inflammatory:
– they open tight junctions: agglutinins (solanaceous, peanuts, soya, etc.), prolamins (wheat, rye, corn, etc. including gliadin), alcohol;
– damage enterocytes: agglutinins, prolamins, legumes;
– or promote intestinal dysbiosis: alcohol, sugars, agglutinins, omega-6, etc.
From scientific evidence to difficult clinical proof
As always, studies carried out concerning nutritional interventions or dietary adaptations are rare, and often methodologically biased. It is difficult to correlate data from basic studies with clinical data. However, “for patients who have tried everything, who have side effects, who do not want to take certain treatments”, hygienic-dietary approaches can be considered, supervised by a nutritionist doctor, particularly when the clinical situation is complex (low BMI , diabetic patient, anxious, etc.). The first concerns fasting: a meta-analysis established that 7 to 10 days of fasting in RA leads to a reduction in symptoms, inflammatory markers and cytokines and markers of intestinal permeability. This fast being complicated to implement and not being maintainable over time, other approaches can be considered, which reduce sugar consumption, glycemic load, alcohol, etc. Other work has looked at the The effectiveness of the Mediterranean diet maintained for 12 weeks in RA, which showed a modest benefit on disease activity and pain. More drastic diets are considered to complement treatments, such as eliminating all processed products, alcohol, etc. or FODMAPs (fermentable oligo-, di-, monosaccharides and polyols) when there are associated intestinal disorders. The approach called ‘paleo autoimmune’ that the speaker presented is a very drastic approach, excluding gluten, nightshades, red meats, cereals, dairy products, refined sugars, legumes from the Mediterranean diet, for three months in order to reduce symptoms. Then, the reintroduction of food categories is done one by one. The choice of these foods is oriented according to the autoimmune nature or not of the disease. “It does not replace treatments but it can reduce certain treatments such as cortisone and improve certain other associated symptoms. Pending rigorous scientific validation, patients must be encouraged to move away as much as possible from the standard Western diet, which is unfavorable for the microbiota.
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