Moderate alcohol consumption during adult life, drinking patterns and breast cancer risk

A well-done analysis by Chen WY et al, published in JAMA assesses the association of moderate alcohol consumption during adult life, drinking patterns, and breast cancer risk. The authors use prospectively collected data from the 105,986 women enrolled in the Nurses' Health Study followed up from 1980 until 2008 with an early adult alcohol assessment and 8 follow ups.

The International Scientific Forum of Alcohol Research comments 'A large percentage of observational prospective studies have shown that women who consume alcohol show an increase in their risk of developing breast cancer. In general, the relation seems to be stronger for women who drink in binges, are also taking post-menopausal hormonal therapy, and/or have low intakes of dietary folate. Most studies have shown that heavier drinkers are at the greatest risk'.

In this study, the risk of breast cancer was found to be modestly increased among consumers of alcohol, even those whose total alcohol consumption was reported to be in the range of 3 to 6 drinks/week. Similar small increases in the risk of breast cancer have been found from alcohol consumption in the majority of previous studies observational studies. A strength of this study was the very large number of subjects, permitting the investigators to attempt to determine if both the amount of alcohol and the frequency of consumption were important in this association; strong effects were not found for either. When adjusting for the cumulative lifetime consumption, there was no effect of the frequency of consumption (1-2, 3-4, or 5-7 days per week).

A weakness in the paper, is a failure to report on the effects of diet and folate intake on the association between alcohol and breast cancer risk; the same investigators have previously shown that folate is a potential moderator of the effects of alcohol on breast cancer risk.

The authors describe well the dilemma that women face regarding alcohol intake, which may increase slightly the risk of breast cancer but markedly decrease the risk of other more common diseases, especially cardiovascular conditions. For example, the authors state that regarding breast cancer, "We did find an increased risk at low levels of use, but the risk was quite small." The International Scientific Forum on Alcohol Research commented on the study "The results are plausible from the pathophysiological point of view: alcohol intake increases estrogen levels and this means that women have a slightly lower risk for osteoporosis and a slightly higher risk for breast cancer. When we tell the public that current data suggest small to moderate amounts of alcohol protect against cardiovascular disease, osteoporosis, diabetes mellitus, and vascular dementia, we should also state that breast cancer risk in women is slightly increased."

The authors of this paper put their findings into perspective when they conclude: "An individual will need to weigh the modest risks of light to moderate alcohol use on breast cancer development against the beneficial effects on cardiovascular disease to make the best personal choice regarding alcohol consumption."