Summary: The authors of this study state that alcohol intake increases breast cancer risk. Epidemiological studies suggest folate may modify this relationship. They examined the relationship among breast cancer, alcohol and folate in the Women’s Health Initiative-Observational Study (WHI-OS). A total of 88,530 postmenopausal women 50–79 years completed baseline questionnaires between October 1993 and December 1998, which addressed alcohol and folate intake and breast cancer risk factors. Cox proportional hazards analysis examined the relationship between self-reported baseline alcohol and folate intake and incident breast cancer.
Results showed that 1,783 breast cancer cases occurred over 5 years. Alcohol was associated with increased risk of breast cancer (RR = 1.005, 95%CI 1.001–1.009). Risk increased with consumption of alcohol (up to 5 g/d, adjusted HR = 1.10, 95%CI 0.96–1.32;>5–15 g/d HR = 1.14, 95%CI 0.99–1.31; and >15 g/d HR = 1.13 95%CI 0.96–1.32). The authors found no significant interaction between alcohol and folate in their adjusted model. They conclude that this study provides no evidence for folate reducing alcohol’s effect on breast cancer risk in postmenopausal women. They add that their results may be due to misclassification of folate intake or the relatively short follow-up period.
Professor R Curtis Ellison comments: This well-done analysis of an observational study is based on the very large number of women in the WHI; its findings provide no support for the theory that adequate folate intake negates any increase in breast cancer risk among women consuming alcohol. The assessment of folate intake was based on food-frequency questionnaires, similar to the ones in the Nurses’ Health Study and other epidemiologic studies that have shown protection from folate intake. Folate intake was based both on foods and supplements, separately and then combined. Most of the potentially confounding variables previously shown to be associated with increased cancer risk (positive family history, use of hormones, earlier menarche, etc.) showed the expected relation with risk of breast cancer. The increase in risk of breast cancer with alcohol on a continuous scale was similar to what has been shown in other studies (the equivalent of about 6% increase for each typical drink per day, assuming 12 grams of alcohol per drink).
The authors point out that the recruitment of women into this study occurred after there had been an increase in the folate intake of the US population from the fortification of cereals and grains, and this could have resulted in fewer women with inadequate folate intake. Further, their follow-up time (5.5 years) may not have been adequate for any protective effect of folate to be seen. While this study showed no reduction in risk of breast cancer, a new clinical trial among patients with coronary disease (Mager A, et al. Impact of homocysteine-lowering vitamin therapy on long-term outcome of patients with coronary artery disease. Am J Cardiol 2009;104:745-749) showed that 400 ug/day of folic acid markedly lowered mortality among subjects with elevated levels of homocysteine. Hence, perhaps we should not give up on folate yet.
Source: Duff CM, Assaf A, Cyr M, Burkholder G, Coccio E, Rohan T, McTiernan A, Paskett E, Lane D, Chetty VK. Alcohol and folate intake and breast cancer risk in the WHI Observational Study. Breast Cancer Res Treat 2009;116:551–562.
