The role of vitamin D deficiency in the pathogenesis of type 2 diabetes mellitus

SummaryPhysical inactivity, poor nutrition practices and obesity contribute significantly to the development of T2DM, however increasing evidence suggests that vitamin D deficiency may play a role in the pathogenesis of T2DM. T2DM manifests as a result of insulin resistance, increased hepatic glucose production and β-cell failure. Vitamin D deficiency increases insulin resistance and decreases insulin secretion in humans and animal models. Conversely, vitamin D supplementation restores insulin secretion and decreases insulin resistance and plasma glucose in humans and animal models. Vitamin D metabolites are thought to play a role in increasing insulin sensitivity and facilitating insulin exocytosis. Vitamin D has also been shown to decrease inflammatory cytokines which play a role in insulin resistance and β-cell apoptosis. Human studies have shown an inverse association between dairy intake and the risk of T2DM. The inverse association between vitamin D and dairy intake and the risk of T2DM may be due to the fact that dairy products are high in more readily absorbable calcium and are often fortified with vitamin D. Vitamin D deficiency is positively associated with insulin resistance and T2DM; however more research is needed to understand this relationship.