Folate intake counteracts breast cancer risk associated with alcohol consumption

ROCHESTER, MINN. — The risk of postmenopausal breast cancer increases among women who regularly consume alcoholic beverages if they have a low intake of folate, a B vitamin, according to a new Mayo Clinic study. However, women who choose to drink can lower their risk of developing breast cancer if they take in the Recommended Dietary Allowance (RDA) of 400 micrograms of folic acid, the synthetic form of folate.

The study, led by Thomas Sellers, Ph.D., a Mayo Clinic cancer epidemiologist, appears in the May 2001 issue of the journal Epidemiology http://www.epidem.com. In this report, Dr. Sellers and colleagues observe that women with dietary folate intake in the lowest 10th percentile and alcohol use above the median of two grams per day had a 59 percent increased risk of breast cancer compared with women who never drank alcohol and whose folate intake was above the median. They also found that breast cancer risk was almost identical for women who drink four or more grams of alcohol per day but have the highest folate intake, and for teetotalers.

The interaction between alcohol and folate has been reported previously in two other large cohort studies. Together with the new Mayo Clinic study, these findings jointly suggest that folate supplementation may be an effective strategy to counteract the risks of breast cancer associated with alcohol-containing beverages.

"Recent surveys of the U.S. population show most people do not get adequate folate," says Dr. Sellers. "Taking a multivitamin should help individuals meet the RDA — just check the label to ensure you’re getting 100 percent of the requirement."

The precise biological mechanisms by which alcohol and folate interact to impact breast cancer risk are less clear, according to the researchers. There is scientific evidence from other studies that low folate levels may lead to poor DNA repair, which has been linked to occurrence of certain cancers.

"It is well established that use of alcohol-containing beverages poses a slight increase in the risk of breast cancer, and family history of breast cancer will increase your risk more," says Dr. Sellers. "Alcohol is metabolized to acetaldehyde, a known carcinogen. People who have adequate folate intake, however, may have a better capacity to repair DNA damage caused by acetaldehyde."

The investigators point out that folate may provide a link that helps women balance the health advantages and disadvantages of temperate alcohol consumption.

"We’d like to offer the benefits of alcohol against cardiovascular disease, but without the consequence of an increased risk for breast cancer," says Dr. Sellers. "This study adds to the growing body of evidence that if you have adequate folate, you are not increasing your risk of breast cancer by drinking in moderation."

Also notable is that since 1998, the FDA has mandated folate supplementation in the United States food supply. Specifically, the FDA requires manufacturers to enrich non-whole-grain products — flour, breads, rolls, buns, farina, corn grits, cornmeal, rice and noodle products — in a birth defect reduction effort http://www.cfsan.fda.gov/~dms/fdafolic.html. However, for women who do not consume these grain products, an alternate method of folate intake would be warranted, according to the FDA, such as

• 1) taking a multivitamin with 400 micrograms of folic acid
• 2) eating enriched, folic acid-fortified breakfast cereals or cereal grain products
• 3) eating natural sources of folate, such as dried beans and peas, dark-green leafy vegetables and fruits

The Study: A Summary

The women in this study are not Mayo Clinic patients. Rather, a group of investigators at the University of Minnesota, some of whom are now at other institutions, initiated this study in January 1986 by mailing a 16-page questionnaire to 98,029 female 55 to 69-year-old Iowa residents randomly selected from the state of Iowa driver’s license list. The 41,836 women who responded form the Iowa Women’s Health Study cohort http://www.cancer.umn.edu/page/research/prevent6.html.

The study participants filled out questionnaires that requested information regarding known or suspected breast cancer risk factors, such as body measurements; history of pregnancy, menstruation, smoking and alcohol use; physical activity; and family history of breast cancer. The survey included questions about food and nutrient intake frequency, including vitamin supplements. Cancer incidence for the Iowa Women’s Health Study was followed through the State Health Registry of Iowa, a part of the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program http://www-seer.ims.nci.nih.gov. After 12 years of follow-up, the researchers found that 1,586 women had developed breast cancer.

For the current report, the Mayo Clinic researchers analyzed the study findings to estimate postmenopausal breast cancer risk associated with certain B vitamins, including folate. Women’s B vitamin intake was categorized in four percentile groups:

• 1) 50th
• 2) 31st to 50th
• 3) 11th to 30th
• 4) less than 10th

Regular alcohol use was categorized as

• 1) never-drinkers
• 2) drinkers of less than four grams per day
• 3) drinkers of greater than four grams per day.

The median daily alcohol use among the cohort is approximately one-half drink, or 4 grams.

The researchers discovered that approximately 30 percent of the women reported regular use of multivitamins, with 8 percent indicating that they regularly ingested B-complex vitamins, including 1 percent who reported using folate supplementation specifically. The median daily folate intake in this study was 294 micrograms per day, or 350 micrograms per day including vitamin supplements.

Note for reporters: As the women in the Iowa Women’s Health Study, the cohort in which the present analysis was conducted, are

• 1) randomly selected members of the general population and thus have no direct patient relationship with the investigators
• 2) participated in this study under strict confidentiality agreements, the participants are not available for news media interviews.

The lead investigator, Dr. Sellers, is available to speak to news media.