According to Breast Cancer Care, women in the UK have a one in nine risk of developing breast cancer at some point in their lives. Nearly 30 percent of all cancers in women occur in the breast.
Researchers from the Cancer Council Victoria and the University of Melbourne in Australia said at the outset of the study that alcohol is a known modest risk factor for breast cancer. They also drew upon studies suggesting that folate could be inversely associated with breast cancer risk.
As to whether folate can counter the adverse effects of alcohol on risk however, they said that the link is "not well established".
To test this, they worked with the Melbourne collaborative cohort study, looking at the alcohol and dietary folate intake of 17,447 Anglo-Australian women resident in Melbourne. The women were recruited to the study between 1990 and 1994, at which time they were aged between 40 and 69 years.
At baseline, the participants' alcohol consumption was assessed through interview and their folate intake through a 121-item food frequency questionnaire.
The women were followed up until diagnosis of breast cancer, death, date of leaving Victoria, or December 31 2003, whichever came first.
Interestingly and in spite of previous evidence, the researchers did not observe a significant association between breast cancer with either alcohol consumption or folate intake.
But when it came to the interaction between alcohol and folate intake, their findings were significant. "Women who had a high alcohol consumption and low intake of folate had an increased risk or breast cancer, but those women who had a high alcohol consumption and moderate to high levels of folate intake had no increased risk," they wrote in the BMJ (2005:331:807).
However, they did draw attention to certain limiting factors, including the small numbers of women who had both high alcohol and high folate levels, the self-reported nature of alcohol consumption data at baseline only, and the fact that folate intake was measured only at baseline without accounting for changes in dietary habits and supplement use.
Since 1995, more than 100 foods have been approved for fortification with folic acid in Australia to help prevent neural tube defects, but compared with the US, where fortification is mandatory in grain products, the impact of this on serum folate levels is reported to be very small.
Despite these limitations, the researchers concluded: "Our results support the hypothesis that alcohol consumption may increase the risk of breast cancer through an interaction with folate and suggest that any adverse effect of alcohol consumption may be reduced by sufficient dietary intake of folate."
In the UK concerns have been raised over the binge-drinking culture amongst women - and particularly young women.
In 2002, 17 percent of UK women were exceeding daily sensible drinking limits on a weekly basis, compared to 10 percent in 1988-9. The percentage of women aged 16 to 20 years who were exceeding weekly limits (14 units) more than doubled, from 15 to 33 percent.
Dr Guy Ratcliffe, medical director of the Medical Council on Alcohol told NutraIngredients.com that there is some danger of women interpreting the study results as meaning they can offset the effects of excessive drinking by upping their folate intake.
In fact, alcohol poisoning from a single binge drinking session (eight units in one sitting for men and six for women) poses the greatest short-term risk, and liver disease the greatest long-term risk.
As to the link between breast cancer and alcohol, Dr Ratcliffe said that the risk is not as high as with other forms of cancer, such as oral cancer. What is more, other factors such as genetics and hormones have more of an impact on breast cancer risk than alcohol.