For female wine drinkers, the medical research community is not making things easy. The debate over whether wine is a risk factor for breast cancer or may actually prevent the disease continues to rage on, thanks to three recent studies. Two of the studies argue that red wine and red wine chemicals are potential breast cancer preventatives. Another study, however, says that any alcohol, wine included, raises the risk of breast cancer, even if consumed moderately.
The latter study, presented in April at the American Association for Cancer Research (AACR) annual meeting in San Diego, was lead-authored by Jasmine Lew, a fourth-year medical student at the University of Chicago and researcher at the National Cancer Institute, which commissioned the study. The research team examined the drinking patterns of 184,418 postmenopausal women. After following the women for seven years, the researchers identified 5,461 cases of invasive breast cancer and compared the rate of cancer versus alcohol-consumption habits.
"What we found was that regular consumption of alcohol, even in moderate amounts, resulted in an increased relative risk of breast cancer," Lew told the audience, adding that the risk remained similar regardless of beverage choice.
According to Lew, the research found that women who drink between one and three drinks a day had a 24 percent increased risk of breast cancer compared to nondrinkers. If they drank more than three, this risk raised to 36 percent. If the women preferred wine, one to three servings meant a 20 percent greater risk and more than three equalled a 41 percent greater risk than nondrinking postmenopausal women.
The study is not publicly available for review yet. It is associated with the National Institutes of Health, and Lew said it has to go through several levels of government clearances before a manuscript can be submitted. But its findings echo similar work reported by Kaiser Permanente's Division of Research last September. Scientists theorize that alcohol affects the levels of hormones such as estrogen and progesterone in postmenopausal women, which may trigger breast cells to become cancerous.
Another recent study, conducted by the Institut Universitaire de Recherche Clinique in Montpellier, France, also identified alcohol as a risk factor for breast cancer. However, after examining a population of women living in the south of France, "where drinking wine is an integral part of the population's dietary habits," researchers found that one glass of wine per day was associated with a 40 percent lower risk of breast cancer. More than a glass evened the risk out to the same levels as nondrinkers.
"The association between alcohol consumption and breast cancer has been largely investigated, but the results published are not entirely consistent," the authors wrote in the June issue of the Annals of Epidemiology, concluding that, "low and regular wine consumption does not increase breast cancer risk." The Montpellier study used methods similar to the National Cancer Institute's research, but looked at only 1,359 women—a much smaller sample.
While observation studies such as these look at lifestyle habits, scientists are also examining the relationship between cancer and wine in the laboratory. A team from the University of Nebraska has looked at the red wine chemical resveratrol as a potential anti-breast cancer agent and found positive results, according to a report published in the July 2008 issue of Cancer Prevention Research.
They found that resveratrol suppresses the metabolism of estrogen, thereby protecting cells from becoming cancerous, in one of many anti-breast cancer activities the red wine chemical exhibits.
"Resveratrol has the ability to prevent the first step that occurs when estrogen starts the process that leads to cancer by blocking the formation of the estrogen DNA adducts," explains co-author Eleanor Rogan, a cancer researcher at the University of Nebraska Medical Center in Omaha. "We believe that this could stop the whole progression that leads to breast cancer down the road."
Rogan and her team noticed that resveratrol suppressed production of the enzyme CYP1B1, as well as the formation of a carcinogen, 2,3,7,8-Tetrachlorodibenzo-p-dioxin. Both chemicals are known risk factors for breast cancer. Furthermore, resveratrol induced production of another enzyme, quinone reductase, which is responsible for reducing the activity of estrogen. By making estrogen inactive, the study finds, resveratrol may decrease the associated risk of breast cancer.
The study results bolster the finding in 2004 by researchers at the University of Porto in Portugal who found that resveratrol, when used in the lab, may help kill off breast cancer cells.
But what was particularly notable for Rogan was that resveratrol appears effective even at small doses. In fact, the suppression of estrogen metabolism was seen in amounts as low as 10 micromoles per liter (the study used increments up to 100 micromoles). Previous studies have shown that the average glass of red wine may contain between nine and 28 micromoles/liter of resveratrol.
The results of the study, however, were met with fierce criticism by cancer awareness campaigners. "It is possible that resveratrol may one day be developed into a cancer-preventing drug, but any beneficial effects it has in red wine are most likely completely outweighed by the alcohol," said Henry Scowcroft, an information manager at Cancer Research UK, an organisation that funds research into the prevention and treatment of cancer.
"From the point of view of cancer prevention, there is no such thing as 'good alcohol.' Overwhelming evidence suggests that, even in moderate amounts, alcohol increases the risk of several cancers including breast cancer," adds Scowcroft. "It is possible that resveratrol, on its own, may one day be developed into a cancer-preventing drug, but any beneficial effects it has in red wine are most likely completely outweighed by the alcohol."
Not all researchers agree with Scowcroft and Lew. Dr. Curtis Ellison, a professor of medicine and public health at Boston University Medical School, said data increasingly shows that for women who do not binge drink, have adequate folate intake, and are not on hormone-replacement treatment, the risk of breast cancer appears to increase only for consumers of more than one and half drinks per day, about 6 to 7 ounces.
Ellison admitted that there may be a weak association for a slight increase in breast cancer risk among light drinkers, but added that, for women, responsible wine drinking is not without benefits. "The net effects are striking, as small amounts of alcohol lower the risk of the more-common causes of death among women, such as heart disease, stroke, hip fracture and dementia," he said.