Medical research on the link between alcohol and breast cancer is yielding new insight but is also making the risks less clear. A new study has found evidence that moderate wine consumption may protect some populations of women against breast cancer. But only women with a certain genetic mutation enjoy the benefits. Women with a different mutation, on the other hand, may be put at greater risk by consuming alcohol.
The study comes from research centers at the Universities of Montreal, Ottawa and Toronto and is slated for publication in The Breast Journal. Breast cancer is the second leading cause of cancer death in Canadian women. The researchers' goal was to validate the 2007 World Cancer Research Fund report that found a convincing link between alcohol consumption and higher rates of breast cancer. Previous studies also suggest that mutated BRCA genes contribute to the risk.
BRCA genes normally operate as tumor suppressors. Mutations, however, may prove harmful. The mutations are hereditary, according to the National Cancer Institute, and can only be detected with genetic screening.
Study lead author Jessica Dennis, a researcher and PhD student at the Dalla Lana School of Public Health, University of Toronto, said the mutations are rare in general, though some ethnicities, such as Ashkenazi Jews, appear to be at greater risk. And not every woman who has a harmful BRCA mutation will develop breast cancer. "Any testing for the BRCA gene mutations should be done in consultation with a doctor," said Dennis. "The mechanism by which alcohol increases breast cancer risk is poorly understood. Likewise, reasons why wine may be protective are unclear."
A total of 857 breast cancer patients took part in the experiment, including 10 BRCA1 and 33 BRCA2 mutation carriers. Their lifestyle choices were recorded, including alcohol consumption. The scientists examined the age at which each woman was diagnosed with breast cancer, and began to develop theories about the pathology of the disease and how it may relate to a lifestyle that includes alcohol consumption.
They found that women with the BRCA1 mutation showed a 62 percent lower likelihood of breast cancer than the general population if they drank wine. In contrast, women with the BRCA2 mutation showed a 58 percent greater risk.
The scientists believe the impact they observed may be due to the presence of the grape polyphenol called resveratrol. "Resveratrol, produced by grape vines in response to injury and found especially in red wine, may mediate the inverse association between breast cancer and wine consumption," the study reported.
Resveratrol binds to estrogen receptors and helps regulate the activity of BRCA1 mutated genes, the researchers believe. BRCA2 is unreceptive to resveratrol, they believe. "Wine consumption may reduce the risk of BRCA1-associated breast cancer, relative to the risk of breast cancer among non-mutation carriers, perhaps through the action of resveratrol," the study concluded.
"If someone is choosing to drink, wine, and especially red wine, may be a good choice," said Dennis. "However, there may be other ingredients in wine that are causing the decrease in risk, or the results may be explained by biases and confounding." Further research is required to explore the connection.
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