The risk of premature death related to cardiometabolic disorders is a pertinent public health concern, which is currently increasing worldwide. These disorders include cardiovascular disease, diabetes mellitus and metabolic syndrome that, when combined, constitute the leading cause of morbidity and mortality worldwide.1 Diabetes mellitus is a micro- and macrovascular disease with subsequent deleterious effects on multiple organ systems. It is recognised as a chronic, debilitating and costly disease associated with major complications that pose a severe burden not only to those who suffer from it but also to their families and society in general.2,3 Diabetes affects more than 220 million people worldwide and has been associated with approximately 5% of all deaths globally each year. Almost 80% of diabetes-related deaths occur in low and middle-income countries. Half of diabetes deaths occur in people under the age of 70 years and 55% of them are in women.4,5 Diabetes risk factors include age, obesity, race, hypertension, impaired glucose tolerance and/or impaired fasting glucose, low HDL cholesterol or high triglycerides, physical inactivity, a family history of diabetes and the presence of the metabolic syndrome. Nowadays, the effects of vitamin D levels have been studied on the reduction on the risk of having cardiovascular disease, type 2 diabetes and metabolic syndrome.6 The metabolic syndrome is a cluster of different metabolic risk factors including central obesity, atherogenic dyslipidaemia (triglyceride level ≥150mg/dl or reduced HDL cholesterol ≤40mg/dl), hypertension, insulin resistance and glucose intolerance.6 Current literature suggests that higher levels of vitamin D are associated with a decrease in the risk of cardiovascular disease, type 2 diabetes and metabolic syndrome.6 In this article we will briefly examine the association, the mechanisms and the potential benefits of increasing serum levels of vitamin D in specific population groups. Different studies have suggested that high levels of vitamin D are associated with a reduced prevalence of metabolic syndrome and type 2 diabetes.7-20 Studies by Ginde et al. and Scragg et al. found a significant association between high levels of vitamin D and reduction on levels of diabetes (88% and 83% respectively).8,17 In a recent meta-analysis Parker et al. found a potentially beneficial role for high levels of 25 hydroxyvitamin D (25OHD) in the prevention of cardiometabolic disorders (in over 85% of the studies included). These findings suggest that vitamin D, among adults and elderly populations, could substantially contribute to halting the current epidemics of cardio-metabolic disorders;6 nevertheless, this meta-analysis by Parker et al. includes solely evidence emanating from observation studies and experimental confirmation is still required. Vitamin D is a fat-soluble vitamin and is known to play an important role in bone and mineral homeostasis, and has also been linked with multiple other pathophysiological mechanisms. Vitamin D receptors are not only expressed in tissues involved in calcium homeostasis but are also found in more than 36 other tissues types.21 Vitamin D obtained from sun exposure, food and supplements is biologically inert and must undergo two hydroxylations in the body for activation (Figure 1).22 Additionally, Vitamin D has other roles in human health, including modulation of neuromuscular and immune function and reduction of inflammation. Serum concentration of 25OHD is the best indicator of vitamin D status and the normal range of values of vitamin D is 30.0–74.0ng/ml. Vitamin D synthesis, metabolism Low levels of vitamin D are prevalent in different populations across the world. Studies published between 1990 and 2009 were conducted in countries such as the United States, Europe, Iran, Australia, India and China, with mixed ethnicities represented.7,17,23-25 Both men and women, including middle aged and elderly populations and living both in rural and urban areas participated in these studies. The potential benefits of high levels of vitamin D in the prevention of cardiometabolic disorders including diabetes, metabolic syndrome and cardiovascular disease, seem to occur in multiple and heterogeneous populations. Nevertheless, older people are especially vulnerable to vitamin D deficiency, due to a decreased physical capacity to synthesise vitamin D from sunlight. Current evidence seems to suggest that abnormal levels of vitamin D are becoming a large public health issue and that positively modifying them might lead to prevention of different pathological conditions including diabetes mellitus and the metabolic syndrome.6,26 Nevertheless, how can this be achieved? First, it is worth considering that 90% of vitamin D synthesis is facilitated by the action of sunlight on the skin.22 In light of the known risk of skin cancer, the benefits and harm of sun exposure must be balanced. Approximately 5–30 minutes of sun exposure, between 10am and 3pm at least twice per week, have been shown to be beneficial in order to raise the levels of vitamin D. Moderate use of commercial tanning beds that emit 2–6% UVB radiation might also be effective; however, the existing evidence in this respect is somewhat controversial and still a subject of debate. Beyond sun exposure, alternative sources of vitamin D are worth considering. National dietary guidelines for vitamin D suggest 200 International Units (IUs) daily intake of vitamin D up to age 50, 400 IUs to age 70 and 600 IUs over age 70. Vitamin D rich foods include fish and fish liver oils, cheese, egg yolks and mushrooms. Some foods like milk, cheese, butter and yogurts are fortified with vitamin D in some countries, including the US and Great Britain. Finally, some recommendations exist for people who do not obtain enough vitamin D through diet or sun exposure, to take a vitamin D supplement on a daily basis; nevertheless, as with sun beds, the evidence on this aspect is limited and this remains a subject of debate.27 In conclusion, positively modifying abnormal levels of vitamin D might be associated with a reduction of cardiometabolic disorders including diabetes and the metabolic syndrome. Although the current evidence looks promising, the benefits of vitamin D levels on the metabolic syndrome and diabetes mellitus need to be further evaluated and confirmed in future prospective studies and clinical trials among different populations. There are no conflicts of interest.