...But while its effect on bones may be its most commonly known property, vitamin D also has many other subtle but very important functions. For example, it reduces the risk of diabetes and certain forms of cancer including ovary, breast, colon and prostate; it has been shown to improve hypertension; help psoriasis; and it drastically reduces the risk of heart disease. There are even some studies that link Alzheimer's disease, depression and multiple sclerosis to low vitamin D levels.
http://www.lef.org/magazine/mag2003/apr2003_report_vitd2.html...vitamin D. Once believed to do little more than regulate bone health, vitamin D is a multi-functional hormone precursor that is increasingly being recognized as a crucial factor in protecting against various cancers, preserving bone integrity, bolstering the immune system, and even warding off debilitating depression.1-3
http://www.lef.org/magazine/mag2007/dec2007_cover_hormones_01.htm...In a breakthrough report, the effects of administering 1,000 IU a day of vitamin D (with calcium) was evaluated in 1,180 postmenopausal women living in the Midwest.10
After four years, the risk of contracting any cancer was 60% lower in the vitamin D (and calcium) group, compared with the placebo arm of the study.
http://www.lef.org/magazine/mag2007/nov2007_report_breastProstate_01.htm