By Robert Bazell, NBC News Chief health and science correspondent
Tonight we report on the latest study showing an increased risk for breast cancer among women who drink alcohol. One reason to pay attention to this study by the Kaiser Permanente Health Group is its size. It looked at more than 70,000 women over an approximately 20-year period. If confirms what may other studies have shown, but when it comes to these kind of associations, the more studies there are the more believable the association becomes.
Women who consume about one drink of alcohol a day have about a 10 per cent increased risk of breast dancer. Those who drink about 3 drinks a day have a 30 per cent increase. One of the study's main conclusions is that it is the alcohol alone that is responsible. It does not matter if the woman drinks wine, beer or spirits. Scientists suspect that alcohol increases production of the female hormone estrogen, which can account for the increased risk of breast cancer (and also for the fact that women who drink moderately have a DECREASED risk of heart disease.)
Should women be concerned? To put these findings in perceptive it is useful to understand that women who smoke a pack of cigarettes a day have about a 2000 per cent increase in their risk for lung cancer, and while the 30 per cent increase is tiny by comparison, it is comparable to the increased breast cancer risk for woman who take long term hormone replacement (HRT)
One reason to pay attention to these relatively low risk increases is that most factors that influence breast cancer risk cannot be controlled. These include age, family history, whether a woman has children and at what age, and the age of onset of her first period. But it is also crucial to understand that these are always numbers for the general population, not for an individual. Lots of women drink heavily and never get breast cancer while the disease often strikes women who never had a drink in their lives.
One of the best guide to understanding breast cancer risk factors comes from the advocacy group: the National Breast Cancer Coalition .
There is a similar guide from the federal government's National Cancer Institute.
But the government guide uses the word "prevention". Unfortunately nothing is known that prevents breast cancer and we should always keep that in mind.