Many studies have been conducted on the relationship between alcoholic drinks and cancer. Digestive system cancers – including cancers of the mouth, throat, esophagus, liver and possibly colon and rectal cancer – are known to be strongly related to alcohol use. Evidence on the relationship between alcohol and breast cancer has been accumulating, but hasn’t been as clear as it is for digestive system cancers. A recent publication, however, addressed a significant problem with the research in the alcohol-breast cancer field, and demonstrated that even those who drink alcohol in small amounts have an elevated risk of developing breast cancer, when compared to those who drink no alcohol at all.
A meta-analysis published in August 2014 in the journal Alcoholism: Clinical and Experimental Research found and analyzed 60 studies conducted prior to 2013 that investigated alcohol’s effect on breast cancer risk. The purpose of the study was to identify those studies that were free of biases. In particular, many studies in the past had classified former or occasional drinkers as abstainers who did not drink alcohol. This misclassification has led to some confusion in published studies, as it obscured the true effect of even small amounts of alcohol, or past alcohol consumption, by inflating the real rates of breast cancer among abstainers. The study was conducted by researchers from the University of Victoria’s Centre for Addictions Research in Canada.
They found only 6 studies that correctly classified former and occasional drinkers versus abstainers. These allowed the researchers to adjust for the bias caused by misclassification. The adjusted data showed a significantly increased risk of breast cancer from consumption of alcohol, even in small amounts. The absolute risk is small, but the risk should act as a caution to people interested in avoiding breast cancer – especially young women. A low-risk drinker, who according to Canadian guidelines has ≤ 2 drinks a day, increases her chance of breast cancer by 8.5%, compared to someone who abstains from alcohol altogether. A hazardous drinker, defined as someone who consumes ≥ 3 drinks per day, increases her risk of developing breast cancer by 37.4%!
Here in the United States, about 3.5% of all cancer deaths (19,500) are alcohol-related, based on data from 2009. Even though there are purported health benefits of consuming alcohol in moderate amounts in diseases such as coronary heart disease, diabetes, and dementia, women should be cautious when it comes to the consumption of alcohol. There really is no level of alcohol use that can be considered “safe,” as it relates to an increased risk of breast cancer.
In order to further explore the relationship between alcohol consumption and breast cancer, more studies that correctly classify former and occasional drinkers versus abstainers should be conducted. In the meantime, physicians should caution patients when they are counseling them on the use of alcohol. As shown in this study, the risk of breast cancer with alcohol use was previously underestimated. We now know that it significantly increases, even with low-level alcohol use.
For women who already have breast cancer, having as little as 3-4 drinks per week may increase rates of breast cancer recurrence and deaths due to breast cancer, especially among postmenopausal women, and women who are overweight or obese. However, it should be noted that as many breast cancer patients die from heart disease, as they do from breast cancer. And there is some suggestion that alcohol consumption after diagnosis may actually reduce mortality from heart disease. Therefore, women with breast cancer should take a comprehensive approach to their decisions about alcohol consumption, and should work on optimizing their diet, weight, exercise habits, and sleep patterns in order to reduce their risks of both breast cancer and heart disease.