Randomized, Controlled Trial of Vitamin D Replenishment in Metabolic Syndrome

Longitudinal observational studies suggest a significant inverse association between vitamin D status and both incident and prevalent metabolic syndrome/type II diabetes. Results from small underpowered trials and post-hoc analyses of data from larger trials designed for bone-specific outcomes suggest that vitamin D may slow the progression to diabetes in adults with glucose intolerance. However, at this time, no randomized trials of sufficient size exist to assess effectiveness.

Importantly, in the investigators' own study of over 10,000 Allina employees, the investigators found that 6% of these employees had levels less than 10 ng/mL, 30% less than 20 ng/ml and 60% less than 30 ng/ml. Recently, the Intermountain Heart Collaborative Study Group reviewed 41,504 patient records with at least one measured vitamin D level. Surprisingly, both the Intermountain and the Allina Employee study demonstrate vitamin D deficiency (≤30 ng/ml) in more than 60% of people tested with only minor differences by gender or age (Plotnikoff GA, Finch M, Dusek JA. Impact of Vitamin D Deficiency on the Productivity of a Health Care Workforce. J Occup Environ Med (in press)).

Furthermore, the Intermountain group demonstrated that vitamin D levels less than 30 ng/ml, compared to levels greater than 30 ng/ml, were associated with highly significant (p <0.0001) increases in the prevalence of diabetes, hypertension, hyperlipidemia, and peripheral vascular disease. Also, those without risk factors but with severe deficiency had an increased likelihood of developing diabetes, hypertension, and hyperlipidemia. The vitamin D levels were also highly associated with coronary artery disease, myocardial infarction, heart failure, and stroke (all p <0.0001), as well as with incident death, heart failure, coronary artery disease/myocardial infarction (all p <0.0001), stroke (p = 0.003), and their composite (p <0.0001).

Numerous prevention efforts are underway to minimize the predicted economic and human burdens from these increasingly common diseases. However, few, if any, prospective clinical trials are underway with vitamin D interventions. This trial is specifically designed to prospectively test the impact of vitamin D replenishment on both metabolic syndrome and insulin resistance.

The 2011 Endocrine Society guidelines assert that vitamin D intakes above the current recommendations may be associated with better health outcomes. However, there is no consensus on the optimal 25(OH)D concentration necessary to minimize metabolic syndrome, insulin resistance and progression to diabetes. This trial is designed to prospectively identify optimal serum levels for reduction of cardiometabolic risk factors.