Can Vitamin D Supplementation Prevent Type 2 Diabetes?

Numerous studies documented that low vitamin D levels are a serious health risk. Despite the sunny climate in Australia, low vitamin D status is becoming increasingly prevalent and people with vitamin deficiency represent more than 30% of the healthy Australian population. Although sun exposure can maintain good vitamin D levels, often sun exposure is limited as people work long hours indoors, and use sunscreen or protective clothing to reduce skin cancer risk when outdoors. Moreover, it is difficult to obtain sufficient vitamin D from food alone; few foods are naturally rich in vitamin D and in Australia, few foods are fortified. While the importance of vitamin D for bone mineralization is well known, it is less clear how vitamin D protects against type 2 diabetes and cardiovascular disease. Every day in Australia around 275 adults develop diabetes and its prevalence continues to rise. We are therefore arguing for a well-designed intervention trial to define the preventive potential and physiological mechanisms of the effects of vitamin D supplementation. In addition, we plan to explore the mechanisms underlying the relationship between vitamin D deficiency and the risk for type 2 diabetes, via its influence on chronic inflammation. Our clinical trial will focus on healthy adults with low vitamin D status and will examine the effects on insulin sensitivity and secretion measured by 'gold standard' methodology when vitamin D is restored to optimum levels. It is in particularly important to determine whether vitamin D affects both or only one of these defects because there is evidence from observational studies that there is a relationship between vitamin D levels and both insulin sensitivity and secretion. The proposed intervention study will potentially supply important evidence on how restoring vitamin D levels may protect against type 2 diabetes. Such findings could have direct relevance for novel approaches to diabetes prevention.