Vitamin B12 deficiency and breast cancer

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BALTIMORE, MARYLAND. Researchers at the Johns Hopkins University report that women with breast cancer tend to have lower vitamin B12 levels in their blood serum than do women without breast cancer. The researchers determined vitamin B12 concentrations in blood samples obtained in 1974 and in 1989 and compared the levels found in 195 women who later developed breast cancer with the levels found in 195 women free of cancer. They found that postmenopausal women with the lowest serum levels of vitamin B12 had a 2.5-4.0 times greater likelihood of being in the breast cancer group than did women with the highest levels. The researchers found no correlation between breast cancer risk and serum levels of folic acid, vitamin B6, and homocysteine.

In a subsequent review of the findings Dr. Sang-Woon Choi, MD of Tufts University points out that serum levels of folate are a poor indicator of levels in tissues and that it may well be that there is a correlation between folate levels in breast tissue and breast cancer risk. Dr. Choi speculates that a vitamin B12 deficiency may lead to breast cancer because it could result in less folate being available to ensure proper DNA replication and repair.

Wu, K., et al. A prospective study of folate, B12, and pyridoxal 5′-phosphate (B6) and breast cancer. Cancer Epidemiol. Biomarkers Prev., Vol. 8, March 1999, pp. 209-17
Choi, Sang-Woon. Vitamin B12 deficiency: a new risk factor for breast cancer? Nutrition Reviews, Vol. 57, August 1999, pp. 250-60