In an April 2006 study researchers discovered a 50% reduction in new cases of breast cancer in women who had the highest level of vitamin D in their blood serum. It is known that Vitamin D deficiency is associated with an increased incidence of breast cancer. According to the Journal of Steroid Biochemistry and Molecular Biology, data from the Harvard Nurses Health Study and the St. George's Hospital Study found that individuals with the highest blood levels of 25-hydroxyvitamin D, or 25(OH)D, had the lowest incidence of breast cancer. One of the authors of the study, Dr. Cedric Garland, states that women can decrease their risk of developing breast cancer by taking 2,000 I.U. (international units) of vitamin D3 daily along with getting 10-15 minutes of sun per day (unless the individual is photosensitive or otherwise needs to avoid sunlight).

Vitamin D3 is available through diet, supplements and, as noted above, through the skin via sunlight. Researchers warn to avoid tanning or burning when out in the sun as this can be harmful. Sources of vitamin D in food include cooked salmon, sardines, vitamin D-fortified milk and cereals, and various other foods. Food is the best way to get enough vitamin D, but supplements are a good substitute if you are unable to obtain a sufficient amount from food.

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