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Intake Of Vitamin D And Calcium Associated With Lower Risk Of
Breast Cancer
Women who consume higher amounts of calcium and
vitamin D may have a lower risk of developing premenopausal breast
cancer, according to a new study. Data from animal studies have
linked calcium and vitamin D to breast cancer prevention, according
to background information in the article. However, epidemiologic
studies on humans have been less conclusive.
Jennifer Lin, Ph.D., of Brigham and Women's Hospital and Harvard
Medical School, Boston, and colleagues assessed 10,578 premenopausal
and 20,909 postmenopausal women age 45 and older who were part of
the Women's Health Study. At the beginning of the study (in 1993
or 1995), the women completed a questionnaire about their medical
history and lifestyle, plus a food frequency questionnaire that
detailed how often they consumed certain foods, beverages and supplements
during the previous year. Every six months during the first year
and then every year after that, participants returned follow-up
questionnaires indicating whether they had been diagnosed with breast
cancer.
Over an average of 10 years of follow-up, 276 premenopausal women
and 743 postmenopausal women developed breast cancer. Calcium
and vitamin D intake were moderately associated with a lower risk
of breast cancer before but not after menopause. The inverse associated
in premenopausal women appeared more pronounced for more aggressive
breast tumors.
"A possible explanation for the evident difference by menopause
status may be related to the joint relationship among calcium,
vitamin D and insulinlike growth factors (IGFs)," they continue.
"In vitro studies have suggested that calcium and vitamin
D exert anticarcinogenic effects on breast cancer cells expressing
high levels of IGF-1 and IGF binding protein 3. Calcium, vitamin
D and IGF binding protein 3 have been shown in vitro to interact
with each other in promoting growth inhibition in breast cancer
cells." Since blood levels of these compounds decline with
age, they would be more prevalent in younger, premenopausal women.
"Further investigation is warranted to study the potential
utility of calcium and vitamin D intake in reducing the risk of
breast cancer," the authors conclude.
The full report is in the May 28 issue of Archives of Internal
Medicine, one of the JAMA/Archives journals. Arch Intern Med.
2007;167:1050-1059.
This study was supported by a grant from the National Cancer
Institute, a grant from the National Heart, Lung, and Blood Institute
and a career development award from the National Cancer Institute.
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