INS and type 2 diabetes mellitus: In relation to type 2 diabetes and cardiovascular risk factors, cross-sectional studies have shown that low plasma concentrations of 25(OH)D are associated with higher fasting serum glucose concentrations [12]; increased insulin resistance [13]; increased first and second phase insulin secretion [14, 15]; higher levels of haemoglobin A1c (HbA1c) [16, 17]; higher blood pressure [18, 19]; and higher levels of triglycerides and lower high-density lipoprotein cholesterol [20].