- The relationship between alcohol consumption and breast cancer remains complicated.
- A new study confirms earlier findings that heavy drinking increases risk for breast cancer, in this case, predominantly among premenopausal women.
- This risk exists independent of alcohol type (beer, wine or spirits).
- Light-to-moderate drinking appears to have little effect on a woman's risk for breast cancer.
In an effort to clarify the relationship between alcohol consumption and the risk of developing breast cancer, a study in the July issue of Alcoholism: Clinical & Experimental Research examines the influence of alcohol intake and type of beverage (beer, wine or spirits) on breast cancer in relation to menopausal status. Findings support previous research showing that heavy drinking increases risk for breast cancer, predominantly among premenopausal women; however, this risk exists independent of alcohol type. Light-to-moderate drinking appears to have little effect on a woman's risk for breast cancer.
"For a number of years, it has been known that a high alcohol intake implies an increased risk of breast cancer," said Morten Grønbæk, professor of alcohol research at the Centre for Alcohol Research at the National Institute of Public Health in Denmark. "The ongoing discussion has been whether or not there is an increased risk among light-to-moderate drinkers as well."
Grønbæk added that he and his colleagues chose to examine what effects the type of alcohol may play in cancer development due to some of their earlier research. "In quite a few previous studies, we have suggested that wine drinkers, in contrast to beer and spirits drinkers, seem to be at a lower risk for some cancers such as upper digestive tract cancer, lung cancer and colon cancer," he said. "There are several plausible biological mechanisms which may explain this, including the fact that wine comprises flavonoids and resveratrol, which have been shown to have 'anti-carcinogenic' properties."
In addition, said Grønbæk, "the reason for looking at menopausal status is that it is very likely that development of breast cancer may have different etiologies depending on hormonal status, and this may be influenced by alcohol intake."
"Prospective studies are particularly useful for studying relations between lifestyle habits such as alcohol consumption and health outcomes such as breast cancer, since the information on the lifestyle habit is collected prior to the development of the health outcome," added R. Curtis Ellison, professor of medicine & public health and director of the Institute on Lifestyle & Health at Boston University School of Medicine. "However, even prospective studies on alcohol and breast cancer can have conflicting results mainly because the association between alcohol and breast cancer is rather weak – unlike smoking and lung cancer, where the association is so strong that it does not require a large number of subjects to demonstrate it – so it requires a huge number of cases to be able to reach a conclusion on the relation."
For this study, researchers used data gathered through the Copenhagen Centre for Prospective Population Studies, a six-cohort examination of health-related issues. The study population comprised 13,074 women, aged 20 to 91 years. Researchers used self-administered questionnaires to ask about alcohol intake, smoking habits, weight and height, physical activity in leisure time, children, use of hormone replacement therapy, menopausal status, and educational levels. The women's health was tracked until diagnosis of breast cancer, death, or end of follow-up for other reasons, whichever came first.
Analysis indicates that alcohol consumption of more than 27 drinks per week – considered heavy drinking – increases the risk of breast cancer in premenopausal women, independent of alcohol type.
"Our study confirms earlier reports that heavy alcohol consumption is a risk for breast cancer," said Grønbæk, "In this case, mainly among premenopausal women. The second main finding is that there seems to be no difference in the effect of the different types of alcohol, which indicates that it is ethanol itself and not the type of drink that is responsible for breast-cancer development."
"In addition," said Ellison, "I believe this study demonstrates very well that light-to-moderate drinking of alcohol has very little effect on a woman's risk of breast cancer. These findings support the results of numerous other studies showing that an increase in breast-cancer risk, if present, is very slight. The study also has enough moderate drinkers of wine in it to be able to say that it does not support the protection against breast cancer from wine consumption."
Grønbæk concurs. "Based on our results, the average reader should not worry too much about light to moderate intake, say, in the area of one to two drinks per day."
"For those women who consume alcohol moderately and responsibly," added Ellison, "this study should help reassure them that they are not having much of an effect on their risk of breast cancer; on the other hand, they are reducing markedly their risk of coronary artery disease and stroke, much more common causes of death than breast cancer. For women who are drinking heavily, this study suggests that they may be increasing their risk of breast cancer. However, there are many other adverse effects of heavy drinking that should also be considered when making decisions about alcohol consumption. Furthermore, there are no data showing [any] beneficial health effects of heavy drinking."
Alcoholism: Clinical & Experimental Research (ACER) is the official journal of the Research Society on Alcoholism and the International Society for Biomedical Research on Alcoholism. Co-authors of the ACER paper, "Alcohol intake, type of beverage and risk of breast cancer in pre- and postmenopausal women" were: Anette Lykke Petri, Michael Gamborg, Susanne Høidrup and Thorkild I.A. Sørensen of the Copenhagen Centre for Prospective Population Studies, Danish Epidemiology Science Centre at the Institute of Preventive Medicine, Copenhagen University Hospital; Anne Tjønneland of the Institute of Cancer Epidemiology at the Danish Cancer Society; and Ditte Johansen of the Copenhagen Centre for Prospective Population Studies, Danish Epidemiology Science Centre at the Institute of Preventive Medicine, Copenhagen University Hospital as well as the Centre for Alcohol Research at the National Institute of Public Health. The study was funded by the Danish National Board of Health, the Danish Medical Research Council, and the Danish Heart Foundation.