The purpose of the research is to describe vitamin D levels and bone status in a rural Wisconsin population. It is probable that individuals of varying age and ethnicity require different amounts of D to achieve optimal status. These likely scenarios will be explored in various populations. We hypothesize that the increase in serum 25(OH)D resulting from daily D3 ingestion is less pronounced with advancing age and different in Native than Caucasian Americans. In addition, the women in the middle age group, between the ages of 55 and 65, will have ultrasound tests completed to assess the impact of the Vitamin D supplementation on cardiovascular health.

Inclusion criteria:

• Healthy, community-dwelling ambulatory women.
• Able and willing to sign informed consent.
• Ages: 20-30, 55-65 or >75
• Baseline serum 25OHD concentration > 10 ng/ml and < 60 ng/ml
• Not pregnant
• 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.
• Willing to utilize sunscreen of SPF-15 or higher when sun exposure for more than 15 minutes is expected.

Exclusion criteria:

• Current hypercalcemia (serum calcium > 10.5 mg/dl) or untreated primary hyperparathyroidism.
• History of nephrolithiasis
• Baseline 24-hour urine calcium > 250 mg
• 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 carcinoma.
• Renal failure; defined as a calculated creatinine clearance (using the Cockroft-Gault approach) of ≤ 25 ml/minute.
• Severe end-organ disease, e.g., cardiovascular, hepatic, hematologic, pulmonary, etc., which might limit the ability to complete this study.
• Treatment with any drug known to interfere with vitamin D metabolism, e.g., phenytoin, phenobarbital.
• Known malabsorption syndromes, e.g., celiac disease, active inflammatory bowel disease, etc.
• Known allergy to chocolate.
• Use of medications known to alter bone turnover including bisphosphonates, estrogen, selective estrogen receptor modulators, parathyroid hormone, testosterone or calcitonin.
• Treatment with high dose vitamin D (≥ 50,000 IU weekly) or any active metabolites of vitamin D, e.g., calcitriol, within six months of screening.
• Use of tanning beds or salons or unwillingness to utilize sunscreen during periods of sun exposure of 15 minutes or longer.