Study to Observe the Capability to Absorb Calcium as an Measure of Adequate Levels of Vitamin D

The specific aims of this project are: 1. To determine the level of 25OHD that maximizes calcium absorption efficiency. 2. To describe the dose response curve of calcium absorption to vitamin D intake and serum 25OHD. This will be a randomized, double-blind, placebo-controlled trial of healthy postmenopausal females to determine the individual and combined effects of calcium and vitamin D supplementation.70 female participants, ages 50 to 70 years of age who are menopausal for over 1 year will be recruited into the study . The patients participation in this study will last about 10 weeks. Approximately 70 subjects from Winthrop University Hospital and the surrounding area will participate in this study. There is a total of 3 visits. Patients will be fasting for all visits. The first visit is a screening visit to determine if the patients qualify. At visit 2, the patients will be given a light breakfast and asked to drink an 8 ounce glass of milk or calcium fortified orange juice containing a calcium isotope. After breakfast, the doctor or nurse will start an intravenous infusion and inject the patient with an IV solution containing a calcium isotope. This is a stable calcium isotope that is not radioactive and has no known toxicity. The patients will also be asked to collect a 24 hour urine and return it to us the next day. The volunteers will be divided into four groups: The first group will take 800 iu daily of vitamin D supplementation. The second group will take 2000 iu daily of vitamin D.The third group will take 4000 iu vitamin D and the fourth group will only take placebos. Visit 3 is essentially the same as visit 2, with subjects returning unused study medication and given new tablets Food frequency questionnaires will be filled out at the initial visit and final visit. Diet will be assessed using 3-day diet history form and NutritionPro analysis software. Patients will be asked to refrain from taking other vitamin D supplements and to continue their usual calcium intake.