A combined analysis of previously published studies did not find an overall effect of dietary folate on risk of breast cancer; there was some suggestion, however, that adequate folate intake may reduce breast cancer risk in women with moderate or high alcohol intake. These results were published in the Journal of the National Cancer Institute.
Breast cancer is diagnosed in over 200,000 women annually in the United States alone. Because it is so prevalent, researchers continue to evaluate ways to prevent breast cancer and to identify patients who may be at a high risk of developing the disease.
Folate is a water-soluble B-vitamin that occurs naturally in foods such as spinach. Its synthetic form-folic acid-is found in dietary supplements and fortified foods.
Though some studies have suggested that higher dietary folate intake may decrease the risk of breast cancer, results have been inconsistent.
To summarize the available evidence about the relationship between dietary folate and breast cancer, researchers conducted a combined analysis of previously published studies.
The studies included in the analysis were all observational studies. In an observational study, the researchers do not assign study participants to a particular treatment group. Rather, the researchers simply observe what happens to study subjects with particular characteristics or behaviors. While well-conducted observational studies can provide very useful information, they tend to be less definitive than randomized clinical trials.
- Results of prospective studies (the type of observational study least prone to bias) found no link between folate intake and breast cancer risk. Similarly, there was no link between blood folate levels and breast cancer risk.
- Four studies evaluated whether alcohol intake modified the relationship between folate and breast cancer risk. The combined results of these studies indicated that high folate intake cut the risk of breast cancer in half among women with moderate or high alcohol consumption. Among women with low or no alcohol consumption, there was no link between folate intake and breast cancer risk.
The researchers conclude, “No clear support for an overall relationship between folate intake or blood folate levels and breast cancer risk was found. Adequate folate intake may reduce the increased risk of breast cancer that has been associated with moderate or high alcohol consumption.”
Reference: Larsson SC, Giovannucci E, Wolk A. Folate and Risk of Breast Cancer: A Meta-analysis. Journal of the National Cancer Institute. 2007;99:64-76.