Study To Understand Fall Reduction and Vitamin D in You

Inclusion Criteria: * Age 70 and older * Non-institutionalized * High risk for falling, defined by a 'yes' response to at least one of the following: * 1\. Have you fallen and hurt yourself in the past year? * 2\. Have you fallen 2 or more times in the past year? * 3\. Are you afraid that you might fall because of balance or walking problems? * 4\. Do you have difficulty maintaining your balance when bathing, dressing, or getting in and out of a chair? * 5\. Do you use a cane, walker, or other device when walking inside or outside your home? * Serum vitamin D \[25(OH)D\] level of 10-29 ng/ml * Able to provide informed consent * Willing to accept randomization to each vitamin D dose * One of the following: * 1\. No vitamin D supplementation at baseline * 2\. Average daily vitamin D supplementation judged by study staff as being consistent with the goal of 1000 IU/day or less at screening and willing to continue the dose unchanged throughout the trial * One of the following: * 1\. No calcium supplementation at baseline * 2\. Average daily calcium supplementation judged by study staff as being consistent with the goal of 1200 mg/day or less at screening and willing to continue the dose unchanged throughout the trial Exclusion Criteria: * Cognitive impairment, defined by Mini-Mental State Exam (MMSE) score \<24 * Hypercalcemia, serum Ca++ 11.0 mg/dl or higher or \>10.5 mg/dl (confirmed) * Hypocalcemia, serum Ca++ \<8.5 mg/dl * Kidney, ureteral, or bladder stones made of calciu…