Improving the Understanding of the Response to Vitamin D Supplementation
Condition: Vitamin D Deficiency
MeSH terms: Vitamin D Deficiency
Intervention: cholecalciferol; Placebo
Intervention description: 2000 IU cholecalciferol gelcaps by mouth daily; matching placebo
Intervention MeSH terms: Cholecalciferol; Vitamin D
Phase: Phase 3
Study type: Interventional
Primary purpose: Diagnostic
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Investigator)
Enrollment: 62.0
Sex: Female
Minimum age: 50 Years
Maximum age: 100 Years
Healthy volunteers: Accepts Healthy Volunteers
Keywords: hypovitaminosis D; vitamin D insufficiency; low vitamin D

Summary:

      It is the investigators hypothesis that the current method of evaluating vitamin D status,
      measuring circulating 25-hydroxy vitamin D is not providing the full metabolic picture, and
      is therefore inadequate. The investigators liken this concept to the evolution of cholesterol
      where initially, total cholesterol was the only measurement, and have since determined the
      importance of HDL, LDL and triglycerides in evaluating patient status. Similarly, the
      investigators feel measurement of other vitamin D components such as sulfated vitamin D,
      circulating vitamin D3 and 3-epi 25-hydroxy vitamin D will offer more comprehensive
      information about a patient's vitamin D status.

      It is our overarching hypothesis that a "vitamin D assay panel," will enhance understanding
      of vitamin D status. It is our expectation that the enhanced understanding based on improved
      measurement capability will ultimately translate to improved definition of vitamin D status
      and need for supplementation on an individual level.
    

Eligibility criteria:

        Inclusion Criteria:

          -  Healthy, community-dwelling ambulatory postmenopausal White, non-Hispanic women

          -  Able and willing to sign informed consent

          -  Baseline serum 25(OH)D concentration of 10-29 ng/mL

          -  Willing to not alter the amount of their baseline vitamin D supplementation during the
             course of this study

          -  Willing to use sunscreen (SPF ≥15) when sun exposure of > 15 minutes is expected

        Exclusion Criteria:

          -  Presence of any measurable circulating 25(OH)D2 on screening measurement

          -  Current hypercalcemia (serum calcium > 10.5 mg/dl) or untreated primary
             hyperparathyroidism

          -  History of nephrolithiasis

          -  Known risk factors for hypercalcemia, e.g., malignancy, tuberculosis, sarcoidosis

          -  History of any form of cancer within the past five years with the exception of
             adequately treated squamous cell or basal cell skin carcinoma

          -  Renal failure; defined as a calculated creatinine clearance (using the Cockroft-Gault
             approach) of ≤ 35 ml/minute

          -  Severe end-organ disease, e.g., cardiovascular, hepatic, hematologic, pulmonary, etc.,
             which might limit the ability to complete this study

          -  Known metabolic bone disease, e.g., Paget's disease, osteomalacia

          -  Treatment with any drug known to interfere with vitamin D metabolism, e.g., phenytoin,
             phenobarbital

          -  Treatment with high dose vitamin D (≥ 50,000 IU weekly) or any active metabolites of
             vitamin D, e.g., calcitriol, within six months of screening

          -  Use of tanning beds or salons or unwillingness to utilize sunscreen during periods of
             sun exposure of 15 minutes or longer

          -  Planned trips/vacations likely to be associated with substantial amounts of sun
             exposure during the course of the study