A recent study by researchers at the Samuel Lunenfeld Research Institute at Mount Sinai Hospital in Toronto suggests that vitamin D, the "sunshine" vitamin, may play a significant role in reducing breast cancer risk. The study results, presented at the 97th Annual Meeting of the American Association for Cancer Research, found the cancer risk reduction was most apparent among subjects exposed to the highest levels of vitamin D at a young age.
Researchers interviewed approximately 576 patients diagnosed with breast cancer and 1,135 people who had no cancer. They found significant reductions in breast cancer in those who had worked in an outdoor job, had taken part in outdoor activities when young, or consumed cod liver oil or milk.
Working an outdoor job between ages 10 to 19 resulted in an estimated 40-percent reduced risk of breast cancer, while frequent outdoor activities between ages 10 to 29 lowered breast cancer risk by an estimated 35 percent.
"These outdoor activities included those that didn't involve physical activity," says Julie Knight, who headed the Mount Sinai research team. "We believe that this is evidence of a reduction of breast cancer risk, associated with earlier exposure to the sun."
Consuming cod liver oil between ages 10 to 19 reduced breast cancer risk by about 25 percent, and drinking at least nine glasses of milk every week between the ages of 10 to 29 reduced the risk by 35 percent. The dietary and lifestyle reductions were significant, even when adjusted for other risk factors for breast cancer such as age, ethnicity, close relatives with breast cancer, age at menarche and age at a woman's first birth.
"What you are exposed to during breast development may be particularly important in determining future breast cancer risk," Knight says. "Current thinking is that exposures during adolescence or before a full-term pregnancy may have a greater effect, as that is when breast tissue is going through the most rapid development."
Knight emphasizes that these findings are preliminary estimates of the risk reduction of breast cancer brought about by vitamin D. The researchers now are looking to solidify these findings and determine whether physical exercise while outdoors is in any way associated with breast cancer.
For more information, contact the American Association for Cancer Research at http://www.aacr.org/.
