Vitamin D Intervention Trial in Healthy Chinese, Phase II

This is a double-blind, randomized, placebo-controlled trial. Based on inclusion and exclusion criteria, 400 eligible volunteers, who were 20-45 years, with 25-hydroxyvitamin D between 12.5-50 nmol/L and BMI between 18.5-28 kg/m2, were enrolled and randomly assigned to placebo or 2000 IU/d vitamin D3 arm, after taking placebo for one week. The study protocol was approved by the Ethics Committee of Huadong Hospital Affiliated to Fudan University, Shanghai and all participants provided written informed consents.In this 2-arm RCT we aimed to systematically investigate the effect of: 1. vitamin D3 supplement on serum 25(OH)D levels and the modifying factors; 2. genetic and non-genetic variants on vitamin D bioavailability; 3. vitamin D3 supplementation on metabolic profiles and circulating bone-turnover markers