Vitamin D in Postmenopausal Women at High Risk for Breast Cancer

This is a phase II study which will enroll 20 postmenopausal women who are at high risk for breast cancer development. The goal is to determine whether a one-year intervention of high-dose vitamin D at 2 different doses (20,000 IU weekly or 30,000 IU weekly) will increase circulating blood levels of vitamin D and to obtain preliminary data on the biologic effects of vitamin D for breast cancer prevention.