It's clear from the wide variety of recent research on vitamin D that this is a valuable part of our nutrition. In a recent trial published in Carcinogenesis (Epub Oct. 31, 2007), women with a higher endogenous (produced in the body, ie. not supplemented) production of vitamin D may have a lower risk of postmenopausal breast cancer.
This population-based case-control study in Germany studied the relationship between serum concentrations of vitamin D and the incidence of postmenopausal breast cancer. Included in the study were 1,394 incident breast cancer cases and 1,365 controls, matched on year of birth and time of blood collection.
Vitamin D concentration was shown to be inversely associated with postmenopausal breast cancer risk. The findings strongly suggest that the better a person's vitamin D supply, characterized by serum measurement, the more protective effect for this type of breast cancer that person would show. The largest inverse associations were in women with low serum concentrations of vitamin D.