Clinical Approaches to Correcting Vitamin D Inadequacy and Maintaining Adequacy

Inclusion criteria

• Community dwelling men and women age ≥ 65 years.
• Able and willing to sign informed consent.
• Serum 25OHD concentration ≥ 10 and less than 60 ng/ml by HPLC.
• Willing to avoid use of cod-liver oil and non-study vitamin D supplementation; standard multiple vitamins containing ≤ 400 IU used no more than once daily will be allowed

Exclusion criteria

• Current hypercalcemia (serum calcium > 10.5 mg/dl) or untreated primary hyperparathyroidism.
• History of nephrolithiasis.
• Screening 25OHD concentration ≥ 60 ng/ml.
• Baseline 24-hour urine calcium > 250 mg if female, > 300 mg if male.
• Known risk factors for hypercalcemia, e.g., malignancy, tuberculosis, sarcoidosis, Paget's disease
• History of any form of cancer within the past five years with the exception of adequately treated squamous cell or basal cell skin cancer.
• Renal failure defined as a calculated creatinine clearance (Cockroft-Gault method) ≤ 25 ml/minute
• Severe end-organ disease, e.g., cardiovascular, hepatic, hematologic, pulmonary, etc., which may limit ability to complete the study
• Known malabsorption syndromes, e.g., celiac disease, radiation enteritis, active inflammatory bowel disease, etc.
• Use of medications known to alter bone turnover including bisphosphonates, estrogen, selective estrogen receptor modulators, PTH, testosterone or calcitonin
• Vitamin D intake greater than 5,000 IU daily
• Treatment with any active metabolites of vitamin D within six months of screening
• Treatment with any drug which may interfere with vitamin D metabolism, e.g., phenobarbital, phenytoin.