It doesn't matter if it's wine or beer, the increased breast cancer risk from drinking three or more alcoholic drinks a day is similar to the increased breast cancer risk from smoking a packet of cigarettes or more a day.

Dr Arthur Klatsky said: “Population studies have consistently linked drinking alcohol to an increased risk of female breast cancer, but there has been little data, most of it conflicting, about an independent role played by the choice of beverage type.”

Dr Klatsky, adjunct investigator in the Division of Research, Kaiser Permanente Medical Care Program, Oakland, USA, and his colleagues studied the drinking habits of 70,033 multi-ethnic women who had supplied information during health examinations between 1978-1985. By 2004, 2,829 of these women had been diagnosed with breast cancer.

In one analysis, the researchers compared the choice of drink amongst women who tended to favour one type of drink over another with women who had no clear preference. They also looked for any association between the frequency of drinking one type of alcoholic drink over another. Finally, they examined the role of total alcohol intake, comparing it with women who drank less than one alcoholic drink a day.

They found that there was no difference in the risk of developing breast cancer between wine, beer or spirits. Even when wine was divided into red and white, there was no difference. However, when they looked at the relationship between breast cancer risk and total alcohol intake, the researchers found that women who drank between one and two alcoholic drinks per day increased their risk of breast cancer by 10% compared with light drinkers who drank less than one drink a day; and the risk of breast cancer increased by 30% in women who drank more than three drinks a day.

When they looked at specific groups, stratified according to age or ethnicity, the results were similar.

Dr Klatsky said: “Statistical analyses limited to strata of wine preferrers, beer preferrers, spririts preferrers or non-preferrers each showed that heavier drinking – compared to light drinking – was related to breast cancer risk in each group. This strongly confirms the relation of ethyl alcohol per se to increased risk.”

He continued: “A 30% increased risk is not trivial. To put it into context, it is not much different from the increased risk associated with women taking oestrogenic hormones. Incidentally, in this same study we have found that smoking a pack of cigarettes or more per day is related to a similar (30%) increased risk of breast cancer.”

Although breast cancer incidence varies between populations and only a small proportion of women are heavy drinkers, Dr Klatsky said that a 30% increase in the relative risk of breast cancer from heavy drinking might translate into approximately an extra 5% of all women developing breast cancer as a result of their habit.

Other studies, including research from the same authors, have shown that red wine can protect against heart attacks, but Dr Klatsky said that different mechanisms were probably at work.

“We think that the heart protection benefit from red wine is real, but is probably derived mostly from alcohol-induced higher HDL (‘good’) cholesterol, reduced blood clotting and reduced diabetes. None of these mechanisms are known to have anything to do with breast cancer. The coronary benefit from drinking red wine may also be related to favourable drinking patterns common among wine drinkers or to the favourable traits of wine drinkers, as evidenced by US and Danish studies.”

Dr Klatsky said that all medical advice needed to be personalised to the individual. “The only general statement that could be made as a result of our findings is that it provides more evidence for why heavy drinkers should quit or cut down.”

He concluded: “This has been fascinating research. Our group has been involved in studies of alcohol drinking and health for more than three decades, including in the area of heart disease. We are fortunate to have data available about a large, multi-ethnic population with a variety of drinking habits.”

- ECCO-the European CanCer Conference