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Breast Cancer Health Center

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Vitamin D May Protect Against Cancer

Researchers Say Supplements May Help Cut Risk of Breast, Colon Tumors

The Role of Supplements continued...

"It may be hard to find and expensive to find it, but you want to take vitamin D-3," Garland says. At the same time, researchers warn against taking large amounts of vitamin D without medical supervision. High doses can cause some side effects, including a dangerous buildup of calcium in the blood.

Garland's new analysis looked at breast cancer rates and vitamin D levels in 1,760 women. The women were divided into five groups depending on their blood levels of vitamin D.

Results showed that women with the highest blood levels of vitamin D were 50% less likely to develop breast cancer than those with the lowest levels. But very few women achieved that.

But even women in the second lowest quintile were 10% less likely to develop breast cancer than those with the lowest levels.

Sun Exposure and Diet

In a separate study, Julia A. Knight, PhD, of the Mount Sinai Hospital in Toronto, and colleagues conducted telephone interviews with 576 women who had been diagnosed with breast cancer and about 1,000 women without cancer. The women, aged 20 to 59, were asked about sun exposure and diet throughout their lives.

Ever working in a job outdoors, thereby exposing women to sunlight, resulted in an estimated 40% reduced risk of breast cancer for women, while frequent outdoor activities between ages 10 to 29 lowered breast cancer risk by an estimated 35%.

Also, taking vitamin D-rich cod liver oil between ages 10 to 19 reduced breast cancer risk by about 35%, and consuming at least nine glasses of milk every week between the ages of 10 to 29 reduced the risk by 25%.

"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 tells WebMD.

High Intake Protects Men, Too

The third study, which appears in the current issue of the Journal of the National Cancer Institute, examined the association between vitamin D and cancer among 47,800 men in the Health Professionals Follow-up Study.

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