With the holiday season in full swing, people are already toasting with vim and vigor — or Pimm’s and ginger, if that’s their drink of choice.
But what the majority of Americans may not realize is that drinking even relatively small amounts of alcohol can be a risk factor for cancer.
The American Society of Clinical Oncology (ASCO), which represents many of the country’s cancer doctors, hopes to change that.
In a statement published Nov. 7 in the Journal of Clinical Oncology, the group points to evidence that even light drinking can increase your risk of mouth and throat cancer, a common type of esophageal cancer, and breast cancer in women.
Moderate and heavy drinking — which includes binge drinking — increase your chances of developing not just these cancers, but several others as well.
The relationship between alcohol and cancer is dose-dependent. This means the more you drink, the higher the risk.
So, what does this mean for your health… and your holiday plans?
Alcohol and cancer by the numbers
The statement — which is based on previously published studies — comes at a time when Americans are drinking more alcohol.
A study published earlier this year in JAMA Psychiatry found that between 2001 to 2002 and 2012 to 2013, the number of high-risk drinkers in the United States increased almost 30 percent.
During that time, the number of people who would be classified as having an alcohol use disorder increased by almost 50 percent.
A survey of 4,016 adults earlier this year by ASCO found that while most Americans know that cigarette smoking and sun exposure are risk factors for cancer, only 30 percent realized that drinking alcohol is a risk factor.
Most also didn’t know that obesity and lack of exercise are risk factors, too.
The cancer risk due to alcohol is high enough that an earlier study estimated that 5 percent of all new cancer cases and 5 percent of all cancer deaths worldwide are due to alcohol.
So how much does alcohol increase your risk of cancer?
It varies with the type of cancer and how much you drink.
The ASCO researchers point to research showing that, compared to nondrinkers, the risk of cancer for heavy drinkers increases by the following amounts:
- Mouth and throat cancer: 5.13 times
- Esophageal squamous cell cancer: 4.95 times
- Voice box cancer: 2.65 times
- Liver cancer: 2.07 times
- Breast (female) cancer: 1.61 times
- Colon and rectum cancer: 1.44 times
This means that on average, heavy drinkers have more than a fivefold higher risk of developing mouth and throat cancer during their lifetime than do nondrinkers.
These numbers are known as relative risks — comparing the risk for one group to that for another.
Relative risks assume that drinking patterns stay constant over the course of the study, although this isn’t always the case in real life.
Researchers defined light drinking as less than one drink per day, moderate as one to four drinks per day, and heavy as more than four drinks per day.
The National Institute of Alcohol Abuse and Alcoholism defines a standard drink as 1.5 ounces of distilled spirits, 5 ounces of wine, or 12 ounces of regular beer.
For moderate drinkers, the increased cancer risks are:
- Mouth and throat: 1.83 times
- Esophageal squamous cell: 2.23 times
- Voice box: 1.44 times
- Liver: 1.08 times
- Breast (female): 1.23 times
- Colon and rectum: 1.17 times
Even light drinkers saw an increased risk of certain cancers. However, for some cancers the risk was about the same as for nondrinkers (liver and colorectal) or lower (voice box):
- Mouth and throat: 1.13 times
- Esophageal squamous cell: 1.26 times
- Voice box: 0.87 times
- Liver: 1.00 times
- Breast (female): 1.04 times
- Colon and rectum: 0.99 times
Alcohol risks in perspective
However, these numbers don’t tell the whole story.
Imagine your boss announces that everyone at the company is going to get a 5 percent raise. Your work was so exceptional, though, that your raise will be 10 percent.
It sounds like a good time to gloat in front of your manager.
But if your manager makes $200,000 a year, her 5 percent raise will be $10,000. While 10 percent of your $50,000 annual salary is only $5,000.
It’s the same way with percent increases in cancer risk. This is why it’s helpful to also know the “absolute risk” for each cancer.
Absolute risk is the chance that you’ll develop cancer over a certain time period, such as during the next 10 years.
The National Cancer Institute lists the lifetime (absolute) risks for the following cancers:
- Mouth and throat: 1.1 percent
- Esophageal (all kinds): 0.5 percent
- Voice box: 0.3 percent
- Liver and bile duct: 1.0 percent
- Breast (female): 12.4 percent
- Colon and rectum: 4.3 percent
So, a woman with no other risk factors has about a 12 percent — or 1-in-8 — chance of developing breast cancer over the course of her lifetime.
This also means that on average, 1 in 8 women in the United States will develop breast cancer at some point in their life.
By combining the absolute and relative risks, you get a better sense of the potential downsides of alcohol.
For moderate drinkers, the adjusted lifetime cancer risks are:
- Mouth and throat: 2.01 percent
- Esophageal squamous cell: 1.12 percent
- Voice box: 0.43 percent
- Liver: 1.08 percent
- Breast (female): 15.25 percent
- Colon and rectum: 5.03 percent
When viewed as a relative risk, moderate drinking increases the risk of esophageal cancer more than breast cancer. But the adjusted lifetime risk of breast cancer is higher because this is a much more common cancer in the first place.
The adjusted lifetime cancer risks for light drinkers are:
- Mouth and throat: 1.24 percent
- Esophageal squamous cell: 0.63 percent
- Voice box: 0.26 percent
- Liver: 1.00 percent
- Breast (female): 12.90 percent
- Colon and rectum: 4.26 percent
So, a woman who drinks less than one glass of wine a day would have a 1-in-23 risk of colorectal cancer over the course of her lifetime.
And a slightly higher risk of breast cancer compared to not drinking at all.
To put it another way, a 40-year-old woman has a 1.45 percent risk of developing breast cancer in the next 10 years, according to BreastCancer.org.
Light drinking increases this risk to 1.51 percent — a 0.06 percent increase.
Using what’s known as “number needed to harm,” this can be viewed as: 1,667 nondrinking women would have to become light drinkers for one new case of breast cancer to occur.
That means 1,666 women would see no difference.
Moderation in all things alcohol
Is this enough to justify giving up the occasional glass of chardonnay?
Or playing the odds and sticking with your nightly martini?
As the ASCO statement explains in detail, the cancer risks of alcohol are quite real.
But it’s not as clear-cut as cigarettes, where any amount of smoking is bad for you.
One of the authors of the ASCO statement told The New York Times that the best way to lower your risk of cancer is to drink less. And if you aren’t already a drinker, don’t start.
But this may not mean you have to give up alcohol completely.
Other research suggests that moderate alcohol drinking may lower your risk of heart disease.
But the research on alcohol and heart disease is mixed. There’s no guarantee of a benefit.
What’s clear, though, is that heavy drinking carries many risks, not just of heart disease and cancer, but also depression, anxiety, alcohol use disorder, and liver disease.
People who already have other risk factors for cancer — whether it’s a family history or obesity — may not want to throw alcohol on top of this risk pile.
But if you’re otherwise healthy, the occasional alcoholic drink might not be that bad.
There are also many other ways to reduce your risk of cancer, such as quitting smoking, exercising more, and eating a healthier diet — all of which don’t carry the risks associated with alcohol.
If you’re wondering if giving up — or cutting back on — alcohol might be a good New Year’s resolution for you, talk to your doctor.