New evidence that red wine lowers risk of breast cancer

Does drinking red wine increase risk of breast cancer? If you have been following the news over the past few years, you might have a hard time justifying that glass of wine with dinner, as we are told that even in moderation the risk of breast cancer increases. But as I have said here before (see post from Nov 2 2011), the whole topic is widely misunderstood and oversimplified, despite the declarations of medical authorities. But a new study helps to shed some light on the subject.

So why is the party line so negative on wine? At first glance, the evidence seems overwhelming: dozens of studies showing that consumption of alcohol in any form – red or white wine, beer, spirits – increases chances of developing breast cancer by about 10% per drink per day. Some of these studies are quite large, with thousands of women surveyed. A closer analysis reveals some serious problems however. To begin with, any time there are dozens of population studies all looking at the same question, we may fairly ask why the question is so difficult to answer. A quick glance reveals one obvious problem: not all the studies find an association of alcohol consumption with breast cancer. Another, more pernicious problem, has to do with a fundamental weakness of population studies: they rely on self reporting, which in the case of alcohol consumption is notoriously unreliable. The result is that heavy drinkers are misclassified as moderate drinkers, suggesting that low levels of drinking are unsafe.

More to the point is the fundamental question of whether red wine is different in terms of risk than other alcoholic drinks. Since women in the U.S. and Britain tend to have mixed drinking patterns – for example, minimal drinking during the week, and a variety of different drinks when they do – it becomes impossible for all practical purposes to know what the effect of regular, moderate consumption of red wine would be. 

It is also difficult to pin down exactly what alcohol does to increase breast cancer risk, but the theory seems to be that it promotes estrogen and so it is primarily estrogen-dependent tumors that account for most of the problem. This latest study attempted to address that by evaluating the effect of compounds in red wine that inhibit an enzyme called aromatase, which converts testosterone into estrogen. Using what is called a crossover prospective trial, they were able to show that consumption of red wine in volunteers had a positive effect, concluding that “red wine is a nutritional [aromatase inhibitor] and may explain the observation that red wine does not appear to increase breast cancer risk.” (emphasis added). So enjoy a glass of red wine with dinner and enjoy life.

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