In many recent studies, we’ve been told that low to moderate consumption of alcohol actually has positive benefits, leading to reduced risks of heart disease and lower overall mortality rates. Now, to balance this somewhat, comes a review study published in the journal Alcoholism: Clinical and Experimental Research.
The researchers, working with epidemiologic data gathered in six different studies from a total of 322,647 women who were evaluated over periods of up to 11 years, found that there was a link between even moderate alcohol consumption and breast cancer. Among the participants in the study, 4,335 of them had a diagnosis of incident invasive breast cancer. The researchers correlated these numbers with the women’s alcohol consumption, as self-reported in food frequency questionnaires they filled out.
What they found was that breast cancer risk increased linearly with increased alcohol intake. That is, among the women who reported drinking moderately (less than 60 grams per day of alcohol), the more they drank, the higher their risk of contracting breast cancer. Breast cancer risk also decreased linearly, meaning that the less they drank, the lower their risk was. Non-drinkers in the survey had the lowest breast cancer risk.
Why alcohol may affect women more than men
First, women’s bodies are on the average smaller than men’s, and larger bodies can absorb more alcohol than smaller ones. Second, studies have shown that women’s livers produce smaller amounts of the enzyme alcohol dehdrogenase than men’s livers do; this enzyme breaks down alcohol, so smaller amounts of it in women means that the alcohol remains in their bodies longer than it does in men’s bodies. Third, women’s bodies contain more body fat and body water than men’s bodies, so there is more likelihood that alcohol can become concentrated in their bodies than in the bodies of men.
That said, most health authorities still say that there is limited risk from drinking alcohol if you consume it wisely. That means a limit of one small drink (two standard units of alcohol) per day for women, and two small drinks per day for men. These recommendations are balanced against reminders that your risk of many diseases (including cancer) goes up the more that you drink, and that “all drinks are not created equal.” That is, a pint of 3% beer may contain 2 units of alcohol, but a pint of 5% beer contains 3 units; a “small” glass of wine in a bar or restaurant (175ml) contains 2 units of alcohol, while a “regular” glass of wine (250ml) contains 3 units.
Problems with this study, and why it’s not definitive
Although the authors of this research found a linear relationship between alcohol consumption in women and incidences of breast cancer, they themselves warn of the dangers involved in believing that their research should be considered a definitive example of “cause and effect.” First, they warn that the epidemiologic data they worked with did not really discriminate between truly moderate drinking and binge drinking, which is important because binge drinking creates significantly higher blood alcohol levels and higher accumulations of acetaldehyde, both known cancer risks. Second, the data they worked with covered only a short period of time, whereas the development of cancer may extend over decades. Third, they admit the problems inherent in relying on self-reported data, due to the tendency in most people to underestimate or underreport the amount of alcohol that they actually drink. Finally, they point out that any increased risk of contracting breast cancer must be weighed against other proven positive effects of moderate alcohol consumption, such as reduced risk of cardiovascular disease and lower incidences of total mortality.
The study authors pointed out these issues to expose some of the difficulties that scientists face when trying to find the “exact causes” of cancer, and to suggest that future research and future epidemiologic studies should address these problems with the data. That is, they should focus more on the actual pattern of drinking – regular small amounts as opposed to episodic large amounts as the result of binging – and record these behaviors, not just the average weekly amount of alcohol consumed. But having expressed these reservations about their findings, the authors also agreed that their results do show that reducing one’s alcohol consumption is a potential way that women can reduce their breast cancer risk.