Vitamin D in Immunomodulation: A Factor in the Pathogenesis of Food Allergies

Background: Vitamin D is known for its regulatory effects on both the innate and adaptive immune systems. Its potential role in modulating allergic responses, including the pathogenesis of food allergies, has gained increasing scientific attention. Objective: To review and synthesize the current evidence on the immunomodulatory effects of vitamin D in the context of food allergy, with a focus on proposed mechanisms and clinical observations. Methods: This narrative review was based on a structured literature search conducted in PubMed, Scopus, and Web of Science, covering 32 publications from January 2010 to April 2024. The search strategy used keywords and combinations such as “vitamin D”, “food allergy”, “immunomodulation”, “gut immunity”, “epithelial barrier”, and “regulatory T cells”. The selection emphasized research exploring immunological pathways, epithelial integrity, and microbiota-related mechanisms. Results: The reviewed literature suggests that vitamin D may contribute to immune tolerance through upregulation of regulatory T-cell responses, suppression of Th2- mediated cytokines, reinforcement of epithelial barrier function, and modulation of gut microbiota composition. Several observational and preclinical studies report associations between vitamin D deficiency and increased susceptibility to food sensitization, particularly in early childhood. However, findings remain inconsistent across populations and study designs, and many results derive from animal models or small-scale human cohorts. There is a lack of large, well-controlled clinical trials. Conclusions:Vitamin D appears to modulate immune pathways relevant to food allergy, including cytokine regulation, mucosal barrier integrity, and microbiota balance. However, current evidence is heterogeneous and largely preclinical, limiting firm conclusions. Future studies should focus on human clinical trials and mechanistic research to clarify causality. Individuals at high risk of vitamin D deficiency may benefit from targeted screening and correction, though clinical guidelines require further validation.