A study in the Journal of the National Cancer Institute linked increased breast cancer risk to drinking between early adolescence and first full-term pregnancy.
Professor Paul Pharoah, Professor of Cancer Epidemiology, University of Cambridge, said:
“The data come from a well-conducted, well-established prospective cohort study.
“What we already know (before these results) is that in a rather general sense drinking alcohol is associated with an increased risk of breast cancer and that the more a woman drinks the greater the risk.
“What we did not know: whether drinking alcohol at different ages has greater or lesser effects. Of particular interest is the time between puberty (menarche) and first pregnancy, when the breast tissue might be particularly susceptible.
“What this study shows is that drinking alcohol between puberty and first pregnancy is associated with an increase in future risk or pregnancy and that this risk is not simply a reflection of the fact that those who drink more in early adulthood tend to drink more in later life.
“There is nothing in the data to suggest that the risk increase from drinking in early adulthood is very different from the risk increase associated with of drinking in later adulthood. Thus the data do not imply that breast tissue is particularly susceptible to the damaging effects of alcohol in early adulthood.
“The paper does suggest that longer duration of drinking between puberty and first pregnancy has a bigger effect, but this may simply reflect an effect of total dose of alcohol.
“What the data do not tell us is whether the risk associated with drinking after puberty persists long term if a woman then stops drinking, or if she reduces her drinking substantially at the time of first pregnancy.
“The headline result is that drinking one unit of alcohol per day (or 12 grams of alcohol per day) was associated with a 13 percent increase in risk (relative risk=1.11 per 10g alcohol per day).
“For a twenty year old woman that equates to a lifetime risk of 11.5 per cent compared to a lifetime risk of 11 per cent for a non-drinker. This is an absolute increase in risk of 5 breast cancer cases per 1000 women.”
‘Alcohol intake between menarche and first pregnancy: a prospective study of breast cancer risk’ by Ying Liu et al., published in the Journal of the National Cancer Institute on Wednesday 28 August 2013.