The Interaction Between Calcium and Vitamin D Intake

Inclusion Criteria: * Healthy women aged 45 and above who have been menopausal at least 1 year (absence of menstrual period for a period of 12 months or more) Exclusion Criteria: * Any chronic medical illness including uncontrolled diabetes mellitus, recent history of myocardial infarction, or heart failure, malignancy, uncontrolled hypertension, obesity (BMI\>35 kg/m2), history of anemia, leukemia, or other hematologic abnormalities, lupus, rheumatoid arthritis, or other rheumatologic disease, or kidney disease of any kind as determined by history and physical examination. * Subjects with osteoporosis of the hip (total hip T-score equal or less than -2.5) or taking medications for osteoporosis such as bisphosphonates will be excluded. * Pregnancy. * Use of medication that influences bone metabolism (i.e. anticonvulsant medications, chronic use of steroids and high dose diuretics). * Significant deviation from normal in medical history, physical examination, or laboratory tests as evaluated by the primary investigator. * Patients with a history of hypercalciuria, hypercalcemia, nephrolithiasis, and active sarcoidosis will also be excluded. * Participation in another investigational trial in the past 30 days prior to the screening evaluation. * Unexplained weight loss of \>15% during the previous year or history of anorexia nervosa. * Medications that interfere with vitamin D metabolism. * Patients with a habitual dietary calcium intake that exceeds 800 mg/day. * Smokers greater than 1 pack per day will be excluded. * Patients reporting alcohol intake greater than 2 drinks daily. * Serum 25-hydroxyvitamin D level \> 75 nmol/L.