Thousands of cases of breast and colon cancers might be averted each year if people in colder climates raised their vitamin D levels, researchers estimate in a new report.
A number of studies have suggested that vitamin D may be important in cancer risk. Much of this research is based on cancer rates at different latitudes of the globe; rates of breast, colon and ovarian cancer, for example, are lower in sunnier regions of the world than in Northern climates where cold winters limit people's sun exposure.
Sunlight triggers the synthesis of vitamin D in the skin, and people who get little sun exposure tend to have lower stores of the vitamin. Complementing these studies are lab experiments showing that vitamin D helps prevent cancer cells from growing and spreading, as well as some clinical trials in which people given high doses of vitamin D showed lower cancer risks.