VITAMIN D AND CANCER.

Vitamin D has been getting a lot of press lately as more and more studies link it with reduced rates of a number of types of cancer (18 at last count) as well as with lower risks of autoimmune diseases, including multiple sclerosis and rheumatoid arthritis. Some experts estimate that thousands of cancer deaths could be avoided in the United States each year if everyone got enough vitamin D.
The connections between vitamin D, cancer and other diseases stem from observations that certain disorders, including some forms of cancer, occur much less frequently in areas with sunny warm climates than they do in places where the sun doesn't shine brightly throughout the year. For example, in 1980 a team of epidemiologists found that rates of colon cancer were much higher in populations that were exposed to the least amount of light (especially in major cities and in high-latitude rural areas).
Bear in mind that our bodies make vitamin D in response to exposure to the ultraviolet B rays of the sun ("B" lightwaves are medium-length, as opposed to the long "A" waves). If you live in an area where the sun isn't strong year round or if you rarely venture outside or always put on sunscreen when you do, you could be shortchanged on vitamin D unless you take supplements. It isn't easy to get enough from your diet. The best sources are fortified milk and cereals, eggs, salmon, tuna, mackerel and sardines. (Unfortunately, most fortified foods provide vitamin D2, a form which is much less well utilized by the body than D3.)
Recent research has suggested that vitamin D regulates cell proliferation and can hold in check the sort of wild cell growth that leads to cancer.


...from Dr. Weil website.