Sunshine, vitamin D supplements needed to prevent breast cancer

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A new study suggests simply taking vitamin D supplements may not be enough to reduce the risk of developing breast cancer in postmenopausal women.

The study led by Engel P and colleagues from National Institute of Health and Medical Research in France, found dietary and supplemental vitamin D intakes were not associated with breast cancer risk.

However, the researchers found in regions with highest ultraviolet radiation exposure, women who had high intake of dietary or supplemental vitamin D were 32 percent less likely to be diagnosed with breast cancer, compared with those who had the lowest vitamin D intake. The association was statistically significant.

For the study published in the Dec 2, 2010 issue of Cancer Epidemiology, Biomarkers & Prevention, the researchers followed 67,721 women enrolled in the French E3N cohort and found the association.  During the 10-year follow-up, 2,871 breast cancer cases were diagnosed.

The researchers concluded that "Our results suggest that a threshold of vitamin D exposure from both sun and diet is required to prevent BC and this threshold is particularly difficult to reach in postmenopausal women at northern latitudes where quality of sunlight is too poor for adequate vitamin D production."

The findings do not mean taking vitamin D supplements is useless because the effect depends upon the dose of vitamin D used. Low doses of vitamin D may not render any protective effect against breast cancer and other health conditions. The finding could mean that the vitamin D supplements used may not be enough to make a difference.

John Cannell, M.D., an expert of vitamin D of Vitamin D Council suggests that about 4000 to 5000 international units of vitamin d per day is needed to maintain a healthy level in the blood.

David Liu

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