The impact of diet on gut microbiome composition: Implications for immune-mediated diseases

Diet is a key modulator of the gut microbiome, which in turn regulates immune function and inflammation. Western dietary patterns, characterized by high intake of fat, sugar, and ultra-processed foods, are associated with gut dysbiosis, increased intestinal permeability, reduced short-chain fatty acid (SCFA) production, and heightened systemic inflammation. In contrast, Mediterranean, high-fiber, plant-based, and fermented-food diets promote microbial diversity, enhance SCFA synthesis, improve gut barrier integrity, and support immune tolerance by modulating regulatory T cell activity. These dietary patterns have demonstrated potential to reduce inflammation and improve outcomes in immune-mediated diseases (IMDs). Current evidence highlights the importance of nutrition strategies to restore healthy microbiome balance and mitigate inflammation, though further clinical trials are needed to confirm efficacy and guide clinical application. This review aims to provide evidence of the negative and positive diets along with the therapeutic potentials within the context of IMDs and emphasizes the need for individualized nutrition.