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The Link Between Alcohol and Breast Cancer

While alcohol consumption is not the most important factor in determining breast cancer risk, recent research shows that most women are not even aware of the connection.

This article was first published in The Montreal Gazette.

Some people see alcohol as something that is good for your health, if you consume it in moderate doses. While almost everyone knows alcohol can cause birth defects if you drink while pregnant or will ruin your liver if you drink excessively over many years, people tend to believe that low levels of alcohol consumption are safe, if not beneficial.

What most people don’t know is that drinking alcohol has been linked to an increased risk of liver, colon, mouth and even breast cancer. Even light drinking, when compared to abstinence, increases the risk of breast cancer.

How alcohol increases breast cancer risk is up for some debate. Breast cancer is a hormone-sensitive malignancy, meaning that high estrogen levels promote its growth. Unsurprisingly, medications like tamoxifen or arimidex that lower or block estrogen have been shown to be important treatments for most types of breast cancer.

Alcohol can increase circulating estrogen levels in pre-menopausal women. Therefore regular alcohol consumption might increase breast cancer risk by raising estrogen levels in the blood. But other factors might be at play. Alcohol also contributes to weight gain, and fat cells contain an enzyme called aromatase that converts testosterone into estrogen. Women with higher body fat percentages have higher estrogen levels and are therefore at higher risk for breast cancer. Other possible mechanisms have been proposed over the years and ultimately alcohol might act in various ways.

Though the exact mechanism is debatable, the surprising point is that most women seem not to be aware of this potential risk factor. A survey from U.K. researchers published in BMJ Open found that the vast majority of women did not identify alcohol as a potential contributor to breast cancer risk. Researchers surveyed 205 women attending a breast clinic or getting a routine mammogram and found that more than 80 per cent were unaware of the link between alcohol and breast cancer. Clinic staff did slightly better, but more than half of the personnel working at these clinics were also unaware of the association.

To be fair, alcohol consumption is not the most important factor in determining breast cancer risk. Genetics, such as BRCA mutations, increase your risk substantially, and age is probably the most important risk factor. Alcohol itself probably accounts for about five per cent of breast cancer riskand with low levels of alcohol consumption — that is, one drink per day — the excess risk is probably small.

But the other interesting part of the survey found that 56 per cent of patients could not correctly identify the alcohol content of four popular drinks. When asked how many “standard” drinks are in typical servings of wine, beer, cider and vodka, most people were wrong. Interestingly, the definition of standard drink is larger in the U.S. and Canada than it is in the U.K. In the U.K., one bottle of wine (12 per cent alcohol and 750 milliliters) has nine servings in it, while here a bottle has five servings.

No matter which rule you want to follow, though, the classic rule of one bottle split between two people might make for a better dinner party, but it means most people are over-pouring and drinking more than they realize.

Some may decide that alcohol’s increased breast cancer risk is too small to justify becoming a teetotaler. But that decision should at least be an informed one and it would appear that many women are not aware of the link and could be drinking more than the daily recommended amount without realizing it. Pour out a bottle of wine into nine glasses and you’ll see what I mean.


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