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NEW YORK (Reuters Health) - Women's dietary intake of vitamin D and calcium doesn't seem to influence their risk of breast cancer, before or after menopause, new research from Canada shows. But the findings do suggest that taking vitamin D in supplement form may be protective against the disease.
Given these new findings on vitamin D supplements, "it looks promising for vitamin D," Laura N. Anderson, one of the study's authors and a doctoral student at Cancer Care Ontario in Toronto, told Reuters Health. "We certainly need more research done in this area," she said.
Some prior studies have suggested that vitamin D may reduce breast cancer risk. Breast cells have receptors for vitamin D, Anderson noted, raising the possibility that the nutrient could help regulate the division and proliferation of these cells; there's also growing evidence that vitamin D could help protect against other types of cancer.
When it comes to diet and supplements, vitamin D and calcium often go hand in hand, she added. Vitamin D is necessary for calcium absorption, so women who want to keep their bones strong as they age are advised to take both; also, many calcium-rich foods, like milk, are enriched with vitamin D.
Anderson and her team sought to separate out the effects of vitamin D and calcium on breast cancer risk by surveying 3,101 breast cancer patients and 3,471 healthy controls about their intake of food and supplements.
The researchers found no relationship between overall vitamin D intake and breast cancer risk; nor was there any association between overall calcium intake and risk of the disease.
However, women who reported taking at least 400 international units of vitamin D every day were at 24 percent lower risk of developing breast cancer.
The findings are published in the American Journal of Clinical Nutrition.
Right now, Anderson noted, health authorities in Canada, the US and other countries are looking at revising the current recommendations on vitamin D intake upward, given that it looks like higher intakes of the vitamin D may be more beneficial.
Further research is needed, she and her colleagues conclude, to investigate the relationship between bigger doses of vitamin D and calcium and breast cancer risk.
SOURCE: American Journal of Clinical Nutrition, online April 14, 2010.