Interrelationship of vitamin D supplementation, adiposity and CVD risk factors in a randomized clinical trial

  • Danik, Jacqueline (PI)

Project Details

Description

In view of the high prevalence of overweight and obese adults in the U.S., finding strategies to curb this epidemic is of public health importance. Obesity augments risk of cardiovascular disease (CVD) and type 2 diabetes among others. Although the definition of vitamin D inadequacy is evolving, and has been derived mostly for bone health, U.S. estimates point to a high prevalence that varies by age, race, and body mass index (BMI). Observational studies suggest that low 25-hydroxyvitamin D (25(OH)D) levels are associated with high BMI and fat mass, but it is unknown whether vitamin D supplementation can alter body composition or adiposity. Despite enthusiasm for the use of vitamin D supplements to reduce fat mass, the hypothesis that vitamin D can modify adiposity remains unproven. Observational studies also link low 25(OH)D levels to CVD risk factors related to obesity, but sequestration of vitamin D in fat tissue may be a confounding factor. The effects of vitamin D supplementation on body composition, adiposity and CVD risk factors, areas identified as high priority by the 2011 Institute of Medicine report, are best tested in a randomized clinical trial setting with longitudinal assessments. Previous trials have been limited by small sample size, insufficient vitamin D dose, inability to separate the effects of calcium from vitamin D, or inadequate ascertainment of body composition. Mounting evidence suggests that vitamin D has multiple effects on calcium and parathyroid hormone related regulation of adipocytes. The VITamin D and OmegA-3 TriaL (VITAL), in its recruitment phase, affords a unique opportunity to investigate the effect of vitamin D on changes in body composition and adiposity (baseline compared to 2 year) and to assess whether changes in CVD risk factors are mediated by these parameters. VITAL is a randomized trial testing 2000 IU/day vitamin D3 and 1 g/day omega-3 fatty acids among 20,000 men and women, with anticipated 5 year follow-up for CVD and cancer. We propose an ancillary study to address 2 hypotheses that vitamin D supplementation 1. lowers total/regional body fat as measured by dual x-ray absorptiometry, improving biomarkers of adiposity (leptin, adiponectin) and 2. impacts CVD risk factors (lipids, glucose tolerance, BP) at least in part through adiposity. We also seek to define how achieved 25(OH)D levels may be affected by body composition and BMI, elucidating how they may influence vitamin D intake needs in the population. (AHA Program: Grant-in-Aid)

StatusFinished
Effective start/end date1/07/1230/06/15

Funding

  • American Heart Association: $198,000.00

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