Just a few drinks a week tied to breast cancer
Women who drink just a few glasses of wine or beer a week may have a slightly increased breast cancer risk, researchers said Tuesday.
Their findings are based on more than 100,000 nurses followed over three decades and add weight to earlier studies linking alcohol to breast cancer and other tumors.
“Even at low levels of alcohol consumption, three to six drinks per week, we found a modest increase in risk,” said Dr. Wendy Chen of Brigham and Women’s Hospital in Boston, whose findings appear in the Journal of the American Medical Association.
And, she added, “There wasn’t a particular period in which it was safe to drink alcohol.”
But before you put away the Pinot, there are some important caveats to consider.
First, it wasn’t a huge effect - about 15 percent higher risk among drinkers compared with teetotalers. For example, even among women who sipped three to six glasses of wine per week, only 3.3 percent would develop breast cancer over 10 years. That compares to 2.8 percent of abstainers and 3.5 percent of women having up to 13 drinks a week.
The Relationship between Wine and Breast Cancer
There has been a cloud of inconsistencies and controversy surrounding the association between moderate wine consumption and Breast Cancer. The one consistent conclusion is that drinking 3 or more drinks per day significantly increases your risk of getting Breast Cancer.
In 1997, a study by Dr. Thun et. al. from the American Cancer Society and Epidemiology Unit at Oxford indicated the benefit of moderate alcohol consumption. They showed that women who were moderate drinkers (one drink per day) had a lower death rate than non-drinkers. The results were statistically significant, with a 21% reduction, but the majority of the benefit came from cardiovascular disease.
However, recently published information is not as favorable with respect to breast cancer. Dr. Smith-Warner et. al. from Harvard studied the association between alcohol consumption and Breast Cancer. Their results showed a linear increase in breast cancer over a wide range of consumption. This group of researchers is highly regarded in the medical research field, and their results are widely accepted. Overall, they concluded that for every 10 grams of alcohol ingested daily, there was a 9% increase in Breast Cancer risk.
There have been other studies that have examined this relationship with mixed results. The only constant seems to be with alcohol consumption over 3 drinks per day, which increases Breast Cancer risk dramatically.
Second, there is still no ironclad proof that alcohol itself is to blame, even though the researchers did their best to rule out competing explanations such as smoking or older age. They also adjusted for other influences on breast cancer risk, like whether or not a woman has had children and breastfed.
“This is an observational study, so we really can’t say anything definite about cause and effect,” Chen, also of Harvard Medical School, told Reuters Health.
Still, she believes the link between drinking and increased breast cancer risk is likely to be causal. Alcohol raises estrogen levels, which play a role in the development of many breast tumors.
A new research report appearing in the October 2011 issue of The FASEB Journal shows that resveratrol, the “healthy” ingredient in red wine, stops breast cancer cells from growing by blocking the growth effects of estrogen. This discovery, made by a team of American and Italian scientists, suggests for the first time that resveratrol is able to counteract the malignant progression since it inhibits the proliferation of hormone resistant breast cancer cells. This has important implications for the treatment of women with breast cancer whose tumors eventually develop resistance to hormonal therapy.
“Resveratrol is a potential pharmacological tool to be exploited when breast cancer become resistant to the hormonal therapy,” said Sebastiano Andò, a researcher involved in the work from the Faculty of Pharmacy at the University of Calabria in Italy.
To make this discovery, Andò and colleagues used several breast cancer cell lines expressing the estrogen receptor to test the effects of resveratrol. Researchers then treated the different cells with resveratrol and compared their growth with cells left untreated. They found an important reduction in cell growth in cells treated by resveratrol, while no changes were seen in untreated cells. Additional experiments revealed that this effect was related to a drastic reduction of estrogen receptor levels caused by resveratrol itself.
“These findings are exciting, but in no way does it mean that should people go out and start using red wine or resveratrol supplements as a treatment for breast cancer,” said Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal. “What it does mean, however, is that scientists haven’t finished distilling the secrets of good health that have been hidden in natural products such as red wine.”
Overall, the researchers estimate that if drinking really does promote breast cancer, it might be responsible for 10 percent of all cases in the U.S.
“The recommendation would not be to stop drinking altogether, but to keep it below the range of three to six glasses a week,” Chen said, adding that going over that limit occasionally - say, during vacation - would be alright.
But that’s not the end of the story because some research suggests a drink a day may be beneficial for the heart.
Just recently, one study of women showed that both light and heavy drinkers lived longer after a heart attack than abstainers. (See Reuters Health story of October 27, 2011.)
“One drink a day is a really good target, assuming that a person can be disciplined about that,” Dr. James O’Keefe, a cardiologist at St. Luke’s Health System in Kansas City, Missouri, told Reuters Health last week.
In an editorial published along with the latest findings, Dr. Steven Narod of the Women’s College Research Institute in Toronto said the results probably aren’t relevant for women with breast cancer. And even for women without the disease, the picture is murky.
“There are no data to provide assurance that giving up alcohol will reduce breast cancer risk,” writes Narod. “Furthermore, women who abstain from all alcohol may find that a potential benefit of lower breast cancer risk is more than offset by the relinquished benefit of reduced cardiovascular mortality associated with an occasional glass of red wine.”
Chen acknowledged those shortcomings and said her group is currently studying the link between drinking and death from any cause, as well as whether people who stop drinking have a lower risk than those who don’t.
SOURCE: Journal of the American Medical Association, online November 1, 2011.