It is well known that the chronic consumption of high doses of alcohol is detrimental to our health. Though liver disease and alcoholism brought on by substance dependence are frequently associated with prolonged alcohol consumption, multiple studies have also linked high alcohol consumption to an increased chance for the development of breast cancer in women.
The authors of a recently published article in the journal of the American Medical Association point out however, that research on the increased risk of breast cancer development has focused on high alcohol consumption and state that low levels of alcohol consumption, which is more prevalent in the United States, has not been "well quantified." As a result, this recent study tried to elucidate whether low levels of alcohol consumption would also translate into an increased risk of breast cancer development.
In discussing their results, the authors state that "we observed an association between even low levels of alcohol consumption and breast cancer risk. The most relevant measure was cumulative average alcohol consumption over long periods of time, and both drinking earlier and later in adult life were independently associated with breast cancer risk." Indeed, binge drinking was also moderately associated, according to the authors.
According to the authors, as little as three to six alcoholic beverages per week (5-9.9g/day) may be associated with an increased risk of breast cancer development. They also observed a ten percent increase in risk with each 10g/day of alcohol intake.
The nature of the association between alcohol consumption and breast cancer is still being investigated; however, the authors share some postulated pathomechanics. They state that the "probable explanation would involve alcohol's effects on circulating estrogen levels," and point to a number of studies that have found an increase of breast cancer types which are estrogen receptor positive (indicating that the cancer cells growth have been likely encouraged by the presence of high levels of estrogen resulting in subsequent estrogen receptor activation).
Like all studies, it is important to also look at the limitations however. Though the study included a vary large group of female nurses with a relatively high retention rate of correspondents over the 20 year study period, tracking correct consumption was done by questionnaires and thus the study was limited to an observational nature. The study population was also predominately white (93.7 percent), but the authors state that "limited available data suggest that the association between alcohol use and breast cancer does not differ by ethnicity."
The results are important because they highlight the risk of alcohol consumption even at small quantities. At the same time, it should be noted however, that the increased risk of breast cancer development was found to be relatively small and thus if another study finds a potential benefit from low levels of alcohol consumption (such as decreased risk of stroke) the two results may very well balance each other out.