Diet, gut microbiome, and type 1 diabetes: from risk to translational opportunity.

The incidence of type 1 diabetes (T1D) has risen sharply in recent decades, implicating the role of environmental factors in disease pathogenesis. Diet, a primary driver of gut microbiome development and composition, along with other environmental exposures, has emerged as a potential modulator of T1D risk and progression. While nutrients, such as certain vitamins, may exert protective effects, the roles of other dietary factors (e.g., early exposure to dietary antigens) remain unclear. Importantly, diet shapes the gut microbiome, which produces immunomodulatory metabolites, including secondary bile acids, short-chain fatty acids (SCFAs), and others that directly influence immune responses. This review presents evidence on how specific dietary factors, including macronutrients (fats, carbohydrates, proteins, such as gluten and milk proteins), fibers, and breastfeeding, affect the gut microbiome and T1D. We also discuss the effects of microbiome-targeted interventions, including probiotics, prebiotics, and fecal microbiota transplantation, on T1D and their potential as future therapeutic strategies. Although animal studies provide compelling mechanistic insights, the results from human trials remain inconsistent, underscoring the urgent need for longitudinal and interventional studies to establish causality. Understanding the complex interplay between diet, the gut microbiome, and immune homeostasis is essential for developing personalized strategies to prevent and treat T1D and delay-related complications.