Vitamin A and its relationship with insulin secretion and diabetes mellitus: a review

Vitamin A is a group of compounds, including retinol, retinal, retinoic acid, and carotenoids. These compounds play essential roles in vision, reproduction, immune regulation, and cellular differentiation. Deficiency remains a global health issue. Beyond its classical functions, evidence suggests that vitamin A plays a role as a modulator of glucose homeostasis and diabetes pathogenesis. This review examined the relationship between vitamin A status and diabetes mellitus, with a focus on pancreatic β-cell function, morphology, and survival. The analysis integrated findings from clinical, epidemiological, and experimental studies published up to 2025. It covered absorption, metabolism, and molecular mechanisms. Evidence shows that vitamin A influences β-cell development, insulin secretion, and protection against oxidative and inflammatory damage. In type 1 diabetes, retinoids reduce autoimmune responses, promote immune tolerance, and preserve β-cell mass. In type 2 diabetes, vitamin A modulates insulin secretion pathways and β-cell gene expression. However, high circulating retinol and retinol-binding protein 4 may contribute to insulin resistance. Carotenoids appear protective. Overall, vitamin A is a key nutritional factor with dual roles in diabetes. It exhibits both protective and pathogenic potential, depending on the context. This review clarifies mechanisms, identifies gaps, and highlights perspectives for nutritional and therapeutic strategies in diabetes management.