The information was extracted from a study of a large group of women with detailed questionnaires on diet, vitamin and mineral intake, medical history and lifestyle from 1992 to 2001. Nearly 3,000 out of the group of nearly 69,000 women developed post-menopausal breast cancer.
Women who consumed the highest levels of calcium (more than 1,250 mg./day) had the lowest rates of breast cancer. Women with dairy consumption starting at two or more servings of dairy products per day had the lowest risks of breast cancer, also. Women who took calcium supplements alone had marginally reduced risk of breast cancer.
Dairy foods are rich in conjugated linoleic acid (CLA,) a fatty acid with anti-carcinogenic effects in experimental studies. Women whose dairy source of calcium was low fat had a lower risk of breast cancer.
Women from states with low UV exposure who consumed over 300 IU/day of vitamin D had a lower risk of breast cancer than those from the same states who consumed less than 100 IU/day.
Vitamin D, calcium, and dairy intake were inversely associated with estrogen receptor positive breast cancer risk, but not estrogen receptor negative risk. There is a suggestion of the benefit of taking Vitamin D for women with estrogen receptor positive breast cancers and further study is needed. (Breast cancers are classified as being either estrogen receptor positive or negative on laboratory testing.)
CONCLUSION: The authors conclude that dietary calcium and some components of dairy reduce the risk of postmenopausal breast cancer. This was especially true among estrogen receptor-positive tumors and requires further study. There was a suggestion of a role of improved vitamin D status in reducing estrogen receptor positive breast cancer.
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