Researchers at the Mayo Clinic Cancer Center, Columbia University, Northwestern University Medical School, and the University of Minnesota evaluated consumption of folate, a nutrient found in green, leafy vegetables, other B vitamins, and regular alcohol consumption with risk of breast cancer among 34,387 postmenopausal women over a 12-year period.

To measure diet, the researchers mailed each participant a food consumption frequency questionnaire. They estimated nutrient intakes and categorized them into four levels. Women in the lowest folate intake category were at a modest increased risk of breast cancer. However, in this study, the women in this category who also consumed alcohol-containing beverages were at the highest risk of developing breast cancer. Overall, 1,586 cases of breast cancer were identified.

"The results of this study suggest that adequate intakes of folate may reduce or eliminate risks of breast cancer associated with consumption of alcohol," explains Thomas A. Sellers, PhD, MPH, principal author of the study and associate director of the Mayo Clinic Cancer Center in Rochester, Minn.

"It is known that alcohol consumption increases the risk of breast cancer," says Heather Feigelson, PhD, an epidemiologist with the American Cancer Society (ACS). "This study suggests a diet rich in folate may help mitigate breast cancer risk in women who consume alcohol in moderation. The highest category reported here is less than two drinks per week."

"It is important to note that folate alone is not associated with risk of breast cancer, but only in diminishing the effect of alcohol intake on breast cancer risk," says Feigelson.

Although this is the fourth study of its kind to examine dietary folate and alcohol and its relation to breast cancer, its results, similar to those of earlier studies, are encouraging, Sellers tells ACS News Today.

"Our analysis was motivated by findings from our colleagues at Harvard on a much larger study of nurses," says Sellers. "[Similar results] have been reported by two other groups, one in Canada and one in Italy. The consistency is a bit surprising, but encouraging that what we’re seeing may be real."

Feigelson points out that Sellers’ study is somewhat unique in its design, which evaluated women without breast cancer and recorded their diet and alcohol patterns using a food consumption frequency questionnaire.

In the study, however, the authors do not have a wide range of alcohol intake categories, notes Feigelson. "Their highest category, more than 4g per day, corresponds to two drinks per week. It is unclear from these data whether the apparent attenuation of risk by folate consumption would hold if the authors could specifically look at higher levels of alcohol consumption, such as one drink per day.

"Regardless of what this research shows," she continues, "alcohol intake is one of the few modifiable breast cancer risk factors. "Women at higher risk of breast cancer may want to limit their consumption of alcohol as indicated by the ACS guidelines."