Alcohol is a well-documented cause of breast cancer. Risk increases by approximately 7% for each 10 g of alcohol consumed daily by adult women.1-3 That is for each drink of beer wine or liquor, risk increases about 7% more compared to a never drinker. About one third of the population of US women never drinks. We have previously written on the mechanism for this increase in risk among adult women (see related posts).
Today we turn to the role of alcohol in early adult life and how it can increase risk of breast cancer by driving normal breast cell along the pathway to begin changes that are precursors or intermediate steps on the way to breast cancer. This evidence is behind our post on how parents can help lower risk for their daughters (see post Early Life and Later Breast Cancer Risk: “Hey, Mom & Dad”)
First, we know that early menarche or first menstrual period, and late age at first birth, are each related to increased risk of breast cancer. In fact, during the interval between menarche and first birth the breast cells accumulate risk (or DNA damage) of progressing to cancer at a faster rate than any other time in the life of a woman. After first pregnancy, the rate of risk accumulation slows and after each subsequent birth it slows more. Finally at menopause, the rate of increase slows even more and is largely driven by circulating estrogen levels after menopause.
We have studied alcohol intake and risk of premalignant breast lesions in a number of settings and note that we see a strong increase in risk when we follow women from late adolescence into their early adult years. Alcohol intake reported in late adolescence and early adulthood increases subsequent risk of the most aggressive premalignant lesions that carry increased risk of developing invasive breast cancer.4,5
For example, our data from the follow-up of over 6000 late adolescent and young adult women and their subsequent risk of biopsy confirmed benign breast disease shows that those who have a family history of breast cancer or if their mother has a history of breast cancer – then drinking alcohol increases the risk of breast cancer precursor lesions.
Women with a family history of breast cancer who drank an average of one drink per day in late adolescence and early adult years have a doubling in their risk of biopsy confirmed benign breast disease compared to those who never drink alcohol. Given much concern among women as to what they can do to lower breast cancer risk or prevent breast cancer in their children (grandchildren, nieces, etc.) these data document that limiting alcohol intake will help avoid the increase in risk that goes with drinking 6.
During the time from menarche to first birth we might also expect lifestyle factors to lower risk – slowing the accumulation of damage to DNA in breast cells and reducing the long-term accumulation of risk of breast cancer. We, and others, have studied physical activity, or exercise, as one possible strategy to reduce risk. A number of studies now show that higher levels of activity from menarche through the premenopausal years is related to substantially lower risk of invasive breast canner.
Bernstein showed as early as 1994 that women who were active in physical exercise for 3.8 hours or more per week had half the risk for beast cancer of women who were not active at all 7. Subsequent studies confirm this protection – both in retrospective recall of activity and in prospective studies such as the Nurses’ Health Study II where women reported their activity through high school and were then followed over time to see who went on to develop breast cancer and who did not 8.
While much interest and research continues to explore how diet may modify the benefits of activity or prevent the adverse effects of alcohol in adolescence on breast cancer risk, to date the studies are few and not yet consistent enough to conclude that we can prevent breast cancer through diet in these years. There is, however, promising evidence that higher fiber intake may reduce risk – and this is safe and recommended approach to a health diet in general 9. Likewise rowing evidence points to soy intake through childhood and adolescent years as the most protective time for this dietary factor to lower risk for beast cancer 10 11.
Related CNiC posts
Further evidence that alcohol causes breast cancer
Literature Cited