Autier and colleagues found that vitamin D deficiency, in the observational studies, was associated with cardiovascular diseases, inflammation, glucose metabolism disorders, infectious diseases, mood disorders, declines in cognitive function, and even all-cause mortality.

With the exception of colorectal cancer, being vitamin D sufficient did not appear to reduce the risk of developing various types of cancer.

Vitamin D sufficiency was associated with a lower risk of cardiovascular events (up to 58%), diabetes (up to 38%), colorectal cancer (up to 33%), and all-cause mortality (29%).

via Vitamin D Dosing: Too Low to Matter?.