A New Paradigm for Vitamin D Sufficiency
Condition: New Biomarkers for Measuring Vitamin D Level
Study type: Interventional

Summary: 
      Although the African-American (AA) population tends to have lower serum 25(OH)D levels
      compared to whites, there is no evidence that the lower 25(OH)D levels in African-Americans
      are harmful. In fact, skeletal health is superior in AA. It is clear that total serum 25(OH)D
      concentrations do not reflect the same risk/benefit ratio in AA compared to white women and
      is, therefore, an inappropriate biomarker in this population.

      The investigators wish to investigate whether free 25(OD)D and Vitamin D Metabolite Ratio
      (VMR, ratio of 25(OH)D to 24,25(OH)2D) are preferable biomarkers to total 25(OH)D. The
      investigators propose a six month randomized double blinded study.
    

Detailed description: 
      The specific aims of this study are as follows:

        1. To establish that free 25(OH)D and VMR are similar in black and white populations.

        2. To characterize the relationships between free 25(OH)D and VMR and two measures of bone
           health (PTH and BMD) in black and white women.

        3. To evaluate whether the relationship of free 25(OH)D (and in parallel analyses, VMR) and
           bone health are stronger than those based on total 25(OH)D.

        4. To evaluate whether free 25(OH)D and VMR respond to vitamin D intake (dose-response) in
           a similar manner to total 25(OH)D.

      The study population is postmenopausal Caucasian women age 60 and older. This six month study
      includes four visits. These results will be compared to those from a study in AA women which
      the investigators are also completing.

      There are two study groups. One group will receive vitamin D supplementation, the other a
      placebo. Subjects will be asked to refrain from taking outside Vitamin D supplements for the
      duration of the study. If the subject is eligible based on the results from the first two
      visits, the subject will be randomized into one of these two groups. Randomized subjects will
      be taking the vitamin D or placebo for a period of 6 months and will have one visit at the 3
      month mark and a final visit at the 6 month mark.

      At the 3-month visit, the following procedures will be conducted: obtain interim medical and
      travel history, vital signs, weight, and height measured by the Harpenden Stadiometer, record
      adverse events and concomitant medications, Fasting blood collection: total 25(OH)D (by
      Diasorin), PTH, serum calcium and creatinine, Fasting urine collection for calcium and
      creatinine, and questionnaires: calcium food frequency questionnaire, quality of life
      questionnaire, falls and flu questionnaires. Subjects will be instructed on how to collect a
      24-hour urine sample (for final visit) and collection container will be dispensed. Unused
      study supplements will be collected and counted, and study supplements will be dispensed
      based on serum 25(OH)D level algorithm.

      At the 6-month visit, in addition to what is completed at the 3-month visit, the following
      procedures will also be conducted:24-hour urine calcium, sodium, oxalate and creatinine;
      mini-mental health examination; physical performance examination (SPPB); and a physical
      activity questionnaire. Unused study supplements will be collected and counted. No further
      supplementation will be provided.
    

Intervention name(s): Vitamin D Supplementation; Placebo; Calcium
Intervention type(s): Dietary Supplement; Other; Dietary Supplement
Intervention description(s): Subjects in this group will receive initial dose of 2400, 3600, or 4800 IU of vitamin D3, based on her serum vitamin D level. Dose will be adjusted at 3 month visit to maintain serum vitamin D level at a desirable level.; Subjects in this group will receive a placebo.; If dietary calcium intake is insufficient in participants of either group, they will be given a calcium supplement in the form of one 600mg pill of CaCO3 to bring them up to an intake of 1200mg/day.
Intervention MeSH terms: Vitamin D; Calcium
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary purpose: Health Services Research
Keywords: vitamin D supplementation; calcium supplementation