No significant effect on bone mineral density by high doses of vitamin D3 given to overweight subjects for one year

The study was a one year, double blind placebo-controlled intervention trial performed at the University Hospital of North Norway. 421 subjects, 21 - 70 years old, were included and 312 completed the study. The subjects were randomized to vitamin D3 40.000 IU per week (DD group), vitamin D3 20.000 IU per week (DP group), or placebo (PP group). All subjects were given 500 mg calcium daily. Serum 25(OH)D, osteoprotegrin (OPG), receptoractivator of nuclear factor-kappaB ligand (RANKL), and BMD at the lumbar spine and the hip were measured before and at the end of the study.At baseline the mean serum 25(OH)D levels were 58 nmol/L (all subjects) and increased to 141 and 100 nmol/L in the DD and DP groups, respectively. After one year, no significant differences were found between the three groups regarding change in BMD, serum OPG or RANKL.Supplementation with high doses of vitamin D for one year does not appear to have a negative effect on BMD in healthy subjects. In order to disclose a positive effect, subjects with low BMD and/or low serum 25(OH)D levels need to be studied.The trial was registered at ClinicalTrials.gov (NCT00243256).A sufficient intake of vitamin D, or sun exposure for production of vitamin D in the skin, is of vital importance for skeletal health, and patients with severe vitamin D deficiency exhibit hypocalcemia and rickets or osteomalacia [1].The skeleton is constantly remodelled. This occurs in small bone remodelling units where the balance between bone resorption by the osteoclasts and bone matrix synthesis by the osteoblasts determines the volume and quality of the bone [2]. It has been known for many years that the activity of the osteoclasts is influenced by the osteoblast, which was clarified by the recent discovery of the osteoprotegrin (OPG)/receptoractivator of nuclear factor-kappaB (RANK)/RANK ligand (RANKL) system [2-6]. Thus, the osteoblasts and the bone marrow stromal cells produce RANKL which activates the osteoclasts by binding to it