Dose-dependent Effects of Vitamin D on Bone Health
Condition: Age-Related Osteoporosis
MeSH terms: Osteoporosis
Study type: Interventional

Summary: 
      We propose to conduct a randomized double blind trial of three doses of vitamin D, 400, 4000,
      and 10,000 International Units (IU) per day, to assess the effect on bone density and
      architecture as assessed by high resolution peripheral quantitative tomography (HR-pQCT)
      measurements at the radius and distal tibia, and standard Dual X-ray absorptiometry (DXA).
      Other measures of bone and calcium metabolism will be assessed. The trial will last as long
      as three years. Approximately 300 healthy men and women, aged 50-70 years of age, will be
      recruited, and randomly assigned to one of the three doses of vitamin D. Other outcome
      variables assessed include quality of life, depression, muscle strength and balance.
    

Detailed description: 
      Hypotheses being tested:

        1. It is hypothesized that vitamin D, in a dose-dependent manner, will suppress parathyroid
           hormone action, resulting in less bone turnover, and decreased cortical porosity,
           leading to improved bone strength as assessed by finite element analysis.

        2. It is hypothesized that vitamin D, in a dose-dependent manner, will increase bone
           density in the central skeleton (spine, hip), as measured by the current standard method
           of dual X-ray absorptiometry (DXA).

        3. It is hypothesized that vitamin D, in a dose-dependent manner, will have an impact on
           quality of life, including indices of depression, as measured by the SF-36 questionnaire
           and an appropriate index of depression.

      Outcomes:

      Primary outcomes:

        -  (1) bone density and (2) strength as measured by HR-pQCT

      Secondary outcomes:

        -  HR-pQCT assessment of bone microarchitecture, examining the relative contribution of
           trabecular and cortical bone. We have chosen four parameters for statistical analysis,
           and have listed them as secondary outcome variables in the section below: cortical
           density, cortical porosity, trabecular density and trabecular number.

        -  bone mineral density as measured by DXA

        -  parameters of calcium metabolism, including biochemical markers of bone turnover and DNA
           to examine possible variations in the genes that control vitamin D metabolism.

        -  quality of life score

        -  depression scale score

        -  balance, grip strength.

        -  fasting glucose and Hemoglobin A1C will also be measured.

        -  Safety will be assessed during the scheduled follow-up visits by obtaining history of
           adverse events, as well as measurements of serum and urine parameters of mineral
           metabolism as described below.

      INTERVENTION DRUG: Vitamin D3 in one of three doses Rationale: For adults under age 70 years,
      the recent Institute of Medicine (IOM) report recommends a total intake of 600 IU vitamin
      D/day will provide all the vitamin D needed for bone health, and since the typical Canadian
      diet contains between 200 and 300 units of vitamin D, the subjects in the lowest dose arm of
      our study will receive 400 IU/day. The other two groups will receive 10,000 IU and 4,000 IU,
      respectively. The 10,000 IU dose is the tolerable upper intake level (TUL) recommended by
      Hathcock et al (Am J Clin Nutr 2007) and 4,000 IU is the IOM's recommended TUL.

      Calcium intake:

      All subjects will have adequate calcium intake as defined by the Institute of Medicine (total
      of 1200 mg/day). A brief dietary history will be taken and subjects will be instructed to
      take an appropriate dose of supplemental calcium if their daily intake is less than 1200
      mg/day (the IOM's Recommended Daily Allowance for this study population).

      Interim analysis (with maintenance of blinding of subjects and investigators as to treatment
      arm):

        -  planned at and of years 1 and 2, as well as the final analysis at year 3.
    

Intervention name(s): Vitamin D
Intervention type(s): Dietary Supplement
Intervention description(s): Three different doses of vitamin D will be administered in a double-blinded fashion. The three doses are 400, 4000, or 10,000 IU/day
Other intervention name(s): Vitamin D3, Cholecalciferol
Intervention MeSH terms: Vitamin D; Ergocalciferols; Cholecalciferol; Vitamins
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Prevention
Keywords: Vitamin D; Bone quality; Bone density; calcium metabolism; High resolution peripheral quantitative computed tomography; Dual X-ray absorptiometry; Quality of life