Is vitamin D supplementation really effective in patients with type 2 diabetes?

Abstract

Vitamin D deficiency is very common in children and adults. More than 50% of Koreans have vitamin D insufficiency. Because vitamin D plays a major role in calcium absorption and bone metabolism, vitamin D deficiency in adults can cause osteopenia, osteoporosis, muscle weakness, and an increased risk of fracture. Furthermore, vitamin D receptors are distributed in most tissues and cells in the body. Several studies suggest that vitamin D deficiency is associated with diabetes and cardiovascular disease. The prevalence of vitamin D deficien cy is higher in type 2 diabetes patients than in nondiabetes patients [1]. Serum 25-hydroxy vitamin D [25(OH)D] concentration, an indicator of vitamin D status, is positively correlated with insulin sensitivity. Also, vitamin D deficiency was associated with increased insulin resistance, low insulin levels, β-cell dysfunction, and metabolic syndrome [2]. The exact mechanism is not known. Vitamin D receptors are present in pancreatic islet cells and insulin secretory capacity was impaired in mice lacking a functional vitamin D receptor [3]. Another possible mechanism is the inverse association