Clinical Briefs: If You're Going to Drink…
With Comments from Russell H. Greenfield, MD. Dr. Greenfield is Medical Director, Carolinas Integrative Health, Carolinas HealthCare System, Charlotte, NC, and Clinical Assistant Professor, School of Medicine, University of North Carolina, Chapel Hill, NC.
Source: Baglietto L, et al. Does dietary folate intake modify effect of alcohol consumption on breast cancer? Prospective cohort study. BMJ 2005;331:807. Epub Aug 8, 2005.
Goal: To determine whether dietary folate intake modifies the risk of invasive breast cancer associated with alcohol consumption.
Design: Prospective cohort study (data taken from the Melbourne collaborative cohort).
Subjects: A total of 17,447 women born in Australia, New Zealand, or the United Kingdom (27-75 years of age at baseline, 99.3% aged 40-69).
Methods: Recruitment occurred between 1990 and 1994 and excluded, among other criteria, women with a history of primary breast cancer. A structured interview was held at baseline to determine the presence of potential risk factors that included alcohol use, frequency of intake, and average quantity consumed. Subjects were classified into one of five categories based on alcohol use: lifetime abstainers, ex-drinkers, and current drinkers with low intake (1-19 g/d), medium intake (20-39 g/d), and high intake (≥ 40 g/d). Participants provided thorough dietary information, including a food frequency questionnaire, and nutrient and energy intakes were calculated based on these foods records. Cases of breast cancer were identified through the Victorian cancer registry. Follow-up continued through the end of 2003.
Results: A total of 537 cases of invasive breast cancer was identified over the course of the study, all but one of which were histologically confirmed. The mean folate intake for participants was 330 µg/d. The overall association between alcohol intake and breast cancer development was not significant in the cohort (but the highest hazard ratio occurred in women ingesting ≥ 40 g/d), nor was there found to be a global protective effect from folate ingestion; however, when evaluating a potential relationship between intakes of alcohol and folate, those women with low folate intakes (200 mg/d) but high alcohol intakes (≥ 40 g/d) had double the risk of invasive breast cancer compared with abstainers with low folate intakes. This increased risk of breast cancer in high users of alcohol was essentially abolished with higher folate intakes (330 and 400 µg/d).
Conclusion: Alcohol ingestion may increase the risk for breast cancer through an association with folate, but the risk can be ameliorated through adequate folate intake.
Study strengths: Prospective nature; analyses adjusted for multiple potential confounders; degree of follow-up; thorough identification of incident cases of breast cancer; authors readily point out weaknesses in their study.
Study weaknesses: Data based on dietary recall and alcohol intake at a single point in time; relatively small number of women identified who drank heavily (n = 538) and an even smaller number who also had high folate intakes (n = 134); imperfect measures of folate intake (did not include multivitamins and supplements); no assessment of women younger than age 40 years.
Of note: Alcohol is not considered a carcinogen, but evidence implicates its metabolite, acetaldehyde, as a co-carcinogen; data strongly suggest that people with low folate intakes who drink alcohol regularly have a higher incidence of colon cancer compared with those who infrequently enjoy alcohol and have high folate intakes; in situ breast cancer was not counted as primary breast cancer; folate fortification of foods is mandatory in the United States, but voluntary in Australia, where more than 100 foods have received approval for such fortification; studies suggest that alcohol intake increases estradiol levels; if folate can indeed modify risk of development of breast cancer for women who use alcohol, it remains unclear whether dose is important, and even whether the effect is early or late stage.
We knew that: A dose-response relationship has been shown between alcohol ingestion and subsequent development of breast cancer in both case-control and cohort studies; the protective effect of folate against breast cancer appears more pronounced in those who are heavy users of alcohol; across individual studies the relative risk of breast cancer increases by 3-16% for each additional 10 g/d ingestion of alcohol; animal data consistently point to a role of alcohol in carcinogenesis.
Clinical import: Although the conclusions of this paper are less than definitive due to methodological limitations, they are nonetheless strongly suggestive, and serve to further emphasize the importance of a well-balanced diet; even more so for those women who regularly enjoy alcohol.
What to do with this article: Keep a hard copy in your file cabinet.
Greenfield RH. If you're going to drink... Altern Med Alert 2005;8(11):131-132.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content