Inclusion Criteria:

1. Age 18 - 75

2. Female

3. White race/ethnicity

4. With history of non-melanoma skin cancer

5. Has 12-16 moles upon skin examination

6. Consents to 6-12 moles biopsies over 2-3 clinic visits (2-4 months)

7. Consents to ingesting oral vitamin D3 or placebo daily for 2-4 months

8. Consents to abstaining from other multivitamins during study

9. Consents to research use of their tissue and blood samples

10. Agrees to apply a sunscreen of SPF 45 during study -

Exclusion Criteria:

1. History or current evidence of hyperparathyroidism, hypercalcemia, renal calculi, or
other renal disease.

2. History or current evidence of malabsorptive illnesses, such as IBD, or liver disease
that would impair uptake or metabolism of vitamin D.

3. History or current evidence of hyperthyroidism that would increase metabolism of
vitamin D.

4. History or current evidence of immunosuppression (cancer, autoimmune disease) or
taking immunosuppressive drugs.

5. Currently taking medications that would affect metabolism of vitamin D
(anticonvulsants, corticosteroids, H2-receptor antagonists).

6. Currently taking medications that predispose to hypercalcemia (digoxin, lithium,
thiazide diuretics) or other electrolyte disturbances (aluminum hydroxide)

7. Pregnancy