A randomized, double-blind, placebo-controlled trial of vitamin D supplementation with or without calcium in community-dwelling vitamin D deficient subjects

BACKGROUND: Although vitamin D deficiency is highly prevalent in the Middle East, very few studies have attempted to measure its health impact. AIMS: We aimed to assess whether vitamin D3 and calcium, either alone or in combination, have health benefit. METHODS: In a 2 × 2 factorial design double-blind, placebo-controlled trial, Community free living adults living in the city of Al Ain, UAE were randomly assigned to receive daily 2000 IU oral vitamin D3 alone, 600 mg calcium alone, oral vitamin D3 (2000 IU per day) combined with 600 mg calcium, or a placebo for 6 months. Primary outcomes were self-rated health and bone turnover markers. RESULTS: Of the 545 randomized, 277 subjects completed 6 months follow up. 25(OH)D levels marginally increased in the two groups received vitamin D3 alone or combined with calcium compared to the decline seen in those who received calcium supplement alone or a placebo. Sub-group analysis revealed that parathyroid hormone (PTH) concentration decreased and Calcium/creatinine ratio increased significantly in the combined vitamin D and Calcium group compared to the vitamin D alone or Calcium alone in contrast to the increase seen in the placebo group [p < 0.05 for between group difference at 6 months]. There were no statistically significant differences between the supplement and placebo groups at the 6 months follow-up in body weight, body mass index (BMI), blood pressure, body pains and general health. CONCLUSION: PTH concentration decreased and calcium/creatinine ratio increased in subjects who received vitamin D and Calcium together compared to those who received vitamin D alone. TRIAL REGISTRATION: NCT02662491, First registered on 25 January 2016 (https://register.clinicaltrials.gov/prs/app/action/SelectProtocol?sid=S00060CE&selectaction=Edit&uid=U0001M6P&ts=3&cx=scu4cb, Last update: 05 August 2019.