Many studies have sought to determine the association between alcohol consumption and the risk of breast cancer in women. Smith-Warner and colleagues analyzed seven prospective studies to assess the relationship between alcohol intake and breast cancer.
The Pooling Project identified studies that had enrolled at least 200 women with breast cancer, assessed dietary intake and contained a validation study of the dietary assessment. Daily intake of alcohol (in grams) was calculated, and the type of alcoholic beverage consumed was recorded.
Alcohol intake ranged from 3.22 to 12.58 g per day among the women who drank alcohol. Nondrinkers accounted for 22.5 to 55.3 percent of the control subjects. Women who drank 30 to 59 g of alcohol per day, on average, were significantly more likely to develop invasive breast cancer (relative risk: 1.41). The relative risk was slightly lower (1.31) for women whose average intake was more than 60 g per day, although this group accounted for less than 1 percent of the women. For an increase in alcohol intake of 10 g per day, the risk of breast cancer increased from 3 to 16 percent (9 percent in the pooled analysis).
The authors conclude that there is a positive association between invasive breast cancer in women and alcohol consumption. The higher risk occurred when the women drank, on average, 2.3 to 4.5 bottles of beer, 2.8 to 5.6 glasses of wine or two to four shots of liquor daily.