By Maureen Williams, ND
Healthnotes Newswire (June 7, 2007)—Many women start thinking about calcium and vitamin D after menopause, but new evidence suggests that paying attention to these nutrients before menopause could protect against breast cancer.
The new study, published in the Archives of Internal Medicine, was drawn from the large, long-term Women’s Health Study. The analysis included information about diet and cancer diagnoses over a ten-year period from 10,578 premenopausal women and 20,909 postmenopausal women.
Some of the richest sources of dietary calcium are green leafy vegetables, such as kale, spinach, and broccoli, as well as sea vegetables such as kelp and dulse. Figs and some nuts and seeds also provide high amounts of calcium. Vitamin D has few natural sources (primarily egg yolk and fish oil) but the body is able to make plenty when it has adequate sun exposure.
Most of the calcium and vitamin D for the women in this study, however, came from fortified dairy foods and supplements. Calcium-fortified orange juice and vitamin D–fortified cereals also contributed to the total intake. This pattern reflects the eating habits of most Americans and people from other Western-influenced cultures.
Calcium and vitamin D intakes were both linked to lower breast cancer risk in premenopausal women, but not postmenopausal women. Compared with premenopausal women with the lowest intake of calcium, those with the highest intake had a 39% lower risk of developing breast cancer; for vitamin D, having the highest intake reduced the risk by 35%. Aggressive breast tumors in particular were less likely to develop in women with high calcium and vitamin D intakes.
“Higher intakes of total calcium and vitamin D were moderately associated with a lower risk of breast cancer among premenopausal women, and the lower risk was more pronounced in more aggressive breast tumors,” the study authors reported, pointing out that this was not the case for postmenopausal women.
“We already knew that women should be trying to get lots of calcium and vitamin D well before menopause to ensure the health of their bones. With these findings, there is even more incentive,” commented Dr. Julianne Forbes, a naturopathic doctor practicing in Maine. “It’s encouraging to see that science is giving us more tools for protecting women against breast cancer. I hope that future research will tell us more about how specific sources of calcium compare in their protective effect.”
(Arch Intern Med 2007;167:1050–9)
Maureen Williams, ND, received her bachelor’s degree from the University of Pennsylvania and her Doctorate of Naturopathic Medicine from Bastyr University in Seattle, WA. She has a private practice in Quechee, VT, and does extensive work with traditional herbal medicine in Guatemala and Honduras. Dr. Williams is a regular contributor to Healthnotes Newswire.
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