This is a three-arm unblinded prospective interventional study of vitamin D supplementation in participants with insufficient vitamin D at three different induction and maintenance dosing regimens (high dose, low frequency; medium dose, medium frequency, and low dose, high frequency). Measurements of serum vitamin D will take place at 4, 8, 12, 24, and 36 weeks, and will be compared to determine which regimen was most effective at achieving and maintaining ideal serum vitamin D levels.

Data obtained from many epidemiological studies suggest that vitamin D deficiency is widespread throughout the world, despite increasing attention to the relationships between vitamin D deficiency and skeletal health as well as many other organ systems. This proposal is designed to optimally replace vitamin D deficient subjects with oral vitamin D solution (Dibase) among a well-characterized population whose mean vitamin D level have been established. In a recent nationwide study, this research team established that the country of Armenia has marginal levels of 25-hydoxyvitamin D among a free-living population of pre- and postmenopausal women: the average level was 19.76 ng/mL with 54% of subjects showing levels that are clearly insufficient. Equally impressive is the finding that fully 20% of women over 65 years of age, have levels that are below 12 ng/mL (< 30 nmol/l).

Following consent, all participants will receive a unique participant identification number, and will then complete a brief questionnaire regarding demographics, selected medical history, and contact information. All participants will then be directed to the EcoSense laboratory, where they will provide blood sample via venipuncture for vitamin D.

For those participants with a 25-hydroxyvitamin D level of less than 30 ng/mL, they will be called back to EcoSense laboratory where they will provide blood sample via venipuncture for calcium, and then brought to the Osteoporosis Center, where they will be randomly allocated into one of three treatment groups.

Participants will be instructed on how to dose the supplement as appropriate for their assigned arm, and then receive 4 weeks of the vitamin D supplement. Participants will return to the Osteoporosis Center at the end of week 4 to obtain an interval history, be assessed for any adverse reactions, compliance, or symptoms of infection or illness. Blood samples will be obtained at weeks 4, 8, 12, 24, and 36 for measurement of 25-hydroxyvitamin D and calcium at the collaborating laboratory as described above, and all participants will be informed of their lab test results as they become available.

Inclusion Criteria:

• Age 18 to 75
• Willing to participate in the study
• No vitamin D supplements for at least 1 year

Exclusion Criteria:

• Not meeting inclusion criteria