Over the last decades, the incidence of autoimmune diseases has been increasing dramatically in Western countries. Among these diseases, we can mention Multiple sclerosis (MS), type 1 diabetes (IDDM), inflammatory bowel diseases (mainly Crohn’s disease) (IBD), systemic lupus erythematosus (SLE), primary biliary cirrhosis, myasthenia gravis (MS), autoimmune thyroiditis (AT), hepatitis and rheumatic diseases (RA), bullous pemphigoid, and celiac disease (CD). Considering the genetic predisposition and environmental factors as a trigger to autoimmune diseases, studies have shown the importance of this last factor, highlighting the importance of diet in the process of autoimmune diseases.
A diet rich in fiber, such as oats, vegetables (broccoli, carrots, cabbage, squash), fruits (avocado, apple, banana, plum), nuts and seeds, legumes (green beans, peas, chickpeas), contributes for the increase of beneficial bacteria in our body’s microbiota. Besides, molecular studies have shown that foods traditionally known as healthy foods, such as fish and elements of the Mediterranean diet, promote intestinal health and immune tolerance. However, it has been observed in the western population the preference for low-quality foods, such as processed and refined foods. The use of antibiotics, insufficient fiber consumption, and limited exposure to beneficial microorganisms are also part of this lifestyle that the population is currently employing, contributing to the increase in autoimmune diseases.
A study comparing the composition of the microbiota in children who had Type 1 diabetes (T1D) and children without the disease, showed that the children with T1D presented a less diverse intestinal microbiota, with fewer Firmicutes (bacteria capable of digest dietary fibers) correlated with decreased of butyrate (product of anaerobic bacterial fermentation, an important source of energy), while children without T1D showed an increase in the phylum of Bacteroidetes (beneficial bacteria that prepare the mucosal immune system and maintain intestinal epithelial homeostasis). Currently, new studies are being conducted to investigate the treatment with probiotics in genetically susceptible children, to prevent T1D.
The mechanisms by which the microbiota relates to autoimmune diseases is still poorly understood, however, studies have shown that some metabolites such as SCFAs (short-chain fatty acid resulting from the degradation process of fibers by commensal intestinal bacteria), omega-3 fatty acids (present in fish, oilseeds, vegetable oils, legumes, among others) and tryptophan (essential amino acid, present in bananas, chickpeas, meat, etc.) can play an important role in the prevention of inflammatory diseases. It is important to mention that tryptophan is also present in milk and soy. However, these foods are not recommended for people who have autoimmune diseases or genetic predisposition to that, since studies have considered tryptophan as a trigger to many diseases, including Hashimoto’s thyroiditis. Also, studies have shown that soy contains flavonoids, which can affect thyroid peroxidase activity leading to a possible thyroid gland growth and goiter.
Have you considered changing your eating habits? What changes in your diet are you willing to make for the sake of your health?
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Blog writer: Vanessa Perdigao