Optimizing Vitamin D Nutrition in Healthy Adults

Inclusion Criteria: Healthy African-American and Caucasian adults aged 18-65 years. Exclusion Criteria: Subjects who are not either African-American or Caucasian. The investigators plan to examine racial differences in response to oral vitamin D dosing and, therefore, have chosen the most affected (African-American) and the least affected (Caucasian) racial groups. Including other racial/ethnic groups may confound the results unless they are studied as separate groups. Any chronic medical illness including diabetes mellitus, history of myocardial infarction or heart failure, malignancy, hypertension (systolic blood pressure [SBP] > 140), obesity (body mass index [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 or taking medications for osteoporosis such as bisphosphonates. Pregnancy. Use of medication that influences bone metabolism (i.e. anticonvulsant medications, steroids, diuretics). Significant deviation from normal in either history, physical examination, or laboratory tests, as evaluated by the primary investigator. Patients with a history of hypercalciuria, hypercalcemia, nephrolithiasis, and active sarcoidosis. 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. Oral contraceptive use will be allowed, but will be appropriately documented. Smokers greater than 1 pack per day. Patients reporting alcohol intake greater than 2 drinks daily. Subjects with baseline 25-OHD level greater than 80 nmol/L or less than 20 nmol/L.