Low levels of vitamin D were associated with higher cancer mortality in people with a history of cancer, a study found.  Inadequate vitamin D levels also were linked to an increase in all-cause mortality and cardiovascular mortality.  Researchers found that vitamin D reduced total cancer mortality by 12%, but did not affect total cancer incidence.  

"Overall, this finding may support the view that low vitamin D concentrations might be a marker for a poor health status rather than a cause of premature mortality."  

Previous research has shown that at least 15 types of cancers have been linked to a lower sun exposure, and that vitamin D more strongly affects cancer mortality than it does incidence, the authors said.

They reported that vitamin D supplementation (400-1,100 IU/day), had little effect on total cancer incidence, but significantly reduced total cancer mortality.

Source:  http://www.medpagetoday.com/Endocrinology/GeneralEndocrinology/46368