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BOSTON, MASSACHUSETTS. Researchers at the Harvard School of Public Health have released the
results of a major study aimed at evaluating the association between blood (plasma) levels of folate (folic
acid), vitamins B6 and B12 and the risk of breast cancer. The study involved 32,826 female nurses who had
blood samples drawn during 1989 and 1990. At the end of 1996 712 of the participants had developed
breast cancer.
The researchers found the women with the highest plasma levels of folate (greater than 14 ng/mL) had a 27% lower risk of breast cancer than did women with a lower level (less than 6.4 ng/mL). The protective effect of folic acid was found to be even more pronounced in women who regularly consumed alcohol (one drink per day or more). Here those with the highest folate levels had an 89% lower risk of breast cancer than did women with low levels.
High plasma levels of vitamin B6 (greater than 95.3 pmol/mL) were associated with a 30% risk reduction as
compared to low levels (less than 28.5 pmol/mL). High vitamin B12 levels were associated with a lower
breast cancer risk among premenopausal women, but not among postmenopausal women. This finding
contradicts that of earlier studies which found a protective effect only among postmenopausal women. It is
interesting that no correlation was observed between the intake of vitamin B12 from food and plasma levels;
a significant correlation was noticed between vitamin B12 intake from supplements and plasma levels.
Plasma homocysteine levels were not associated with breast cancer risk. The researchers conclude that
folic acid and vitamin B6 may help prevent breast cancer and that ensuring an adequate intake of these
vitamins either from food or supplements may reduce breast cancer risk.
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