Drinking Alcohol Can Raise Cancer Risk. How Much Is Too Much?

Jun 19, 2018
Originally published on June 19, 2018 6:37 pm

A little bit of alcohol has been shown to be protective of heart health. But how does drinking influence cancer risk?

A new study finds that light drinkers have the lowest combined risk of developing cancer and dying prematurely — even lower than people who don't drink at all. But here's the rub: In this study, "light" drinking is defined as one to five drinks per week.

"It seems to reassure light drinkers," says study co-author Andrew Kunzmann, a researcher at Queen's University Belfast.

Researchers studied about 100,000 adults who lived in cities across the U.S., including Birmingham, Ala.; Boulder, Colo.; Los Angeles; and Pittsburgh. The participants were in their mid-50s to early 70s when the study began, and they each completed a survey about their alcohol consumption. Researchers tracked their health for about nine years, and they found that the more a person drank, the higher their risk of getting cancer and dying.

"We definitely think [the findings] give a bigger picture of what's going on," Kunzmann says. For this study, he collaborated with researchers at the National Cancer Institute in the U.S. The study is published in the scientific journal PLOS Medicine.

The study adds to the evidence that cancer risk may rise when people drink more than one drink per day, but the increase is modest. Moderate drinkers in the study had about a 10 percent increased risk of getting cancer.

Not surprisingly, the study finds that heavy drinkers are most at risk. For instance, men who drank three or more drinks per day were three to four times more likely to develop cancer of the esophagus and liver cancer. Other alcohol-related cancers include colorectal cancer and breast cancer in women.

"This study reinforces [the evidence] that people who drink a lot have higher rates of cancer and higher rates of dying from those cancers," says Noelle LoConte, an oncologist and associate professor at the University of Wisconsin. She was not involved in the study, but NPR asked her to review the evidence.

The study comes at a time when the American Society of Clinical Oncology, a group of cancer doctors, is trying to spread awareness about the risks of excessive alcohol consumption. LoConte is the lead author of the group's recent statement calling for policies aimed at reducing alcohol consumption.

"We're not proponents of complete abstinence. There probably is an amount of drinking that's OK," LoConte says. "But from a cancer-prevention standpoint, drinking the least amount of alcohol possible would be the best strategy."

Many studies have pointed to the risks of excessive drinking, yet "we do not think that most Americans are aware of the link between alcohol and cancer," LoConte says.

Most people know that too much sun exposure increases the risk of skin cancer and that smoking increases the risk of lung cancer. But a survey done by ASCO last year found that 7 in 10 adults did not recognize drinking alcohol as a risk factor for cancer.

When it comes to the lifestyle factors and habits that people can control — or change — to reduce their risk of disease, alcohol is pretty high up on the list. "Alcohol is estimated to be the third-largest modifiable risk factor for cancer," says Susan Gapstur, an epidemiologist with the American Cancer Society.

About 19 percent of cancers are linked to smoking, 8 percent are linked to obesity or excess body weight — and about 5 percent are linked to alcohol.

Alcohol is also estimated to be the third-largest contributor to overall cancer deaths in both men and women, Gapstur says. "Strikingly, alcohol is estimated to account for 39,060 breast cancers [in the U.S.] per year in women," she says.

One step toward cutting back is to be more aware — and more realistic — about how much you drink. "The first thing we need to talk about is: What is a drink?" says LoConte.

A drink is a single shot of liquor, 5 ounces of wine or 12 ounces of beer. It's easy to consume more than you realize. Some mixed drinks contain multiple shots of liquor, and some craft beers have higher concentrations of alcohol.

Current guidelines recommend that women consume no more than one drink per day, and men consume no more than two drinks per day.

But LoConte says this may turn out to be too much. "I think this study, as I reviewed it, looked like a safer amount would be one drink a day for everybody, regardless of gender," LoConte says.

At least that's what the study suggests. More research is underway.

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MARY LOUISE KELLY, HOST:

All right, a study published today in the scientific journal PLOS offers insight into the complex relationship between drinking alcohol and the risk of cancer and premature death. The study finds that light drinkers have the lowest risk. NPR's Allison Aubrey reports.

ALLISON AUBREY, BYLINE: Researchers studied about a hundred thousand people who lived in a bunch of U.S. cities including Birmingham, Boulder, LA and Pittsburgh. They were in their mid-50s to early 70s when the study began, and all completed surveys about their alcohol consumption. Researchers tracked their health for about nine years and found that the more a person drank, the higher their risk of cancer and cancer-related death. Andrew Kunzmann of Queen's University Belfast in Ireland is the study author.

ANDREW KUNZMANN: We definitely think it gives a bigger picture about what's going on here.

AUBREY: So how much is too much? This study suggests that light drinkers have the lowest combined risk of cancer and premature death, even lower than people who never drink, though it's not clear why. In this study, light drinking was defined as one to five drinks per week.

KUNZMANN: It seems to reassure light drinkers.

AUBREY: The study suggests that cancer risk starts to increase when people drink more than a drink a day, but the increase is modest. Moderate drinkers in the study had about a 10 percent increased risk of getting cancer. It's heavy drinkers who are most at risk. For instance, men who drank three drinks or more per day were 3 to 4 times more likely to develop cancer of the esophagus and liver cancer. The study comes at a time when some of the top cancer doctors in the U.S. are trying to get the word out about the risks of drinking too much. Here's oncologist Noelle LoConte of the University of Wisconsin. She's the lead author of a recent statement from the American Society of Clinical Oncology.

NOELLE LOCONTE: We're not proponents of complete abstinence. There probably is an amount of drinking that's OK. But from a cancer-prevention standpoint, if you want to prevent cancer via diet, then drinking the least amount of alcohol possible would be the best strategy. And this study reinforced that.

AUBREY: As have other studies. But LoConte says the message has yet to get out. Most people are aware of the link between, say, skin cancer and sun exposure and lung cancer with tobacco use. But when it comes to drinking alcohol...

LOCONTE: We do not think that most Americans are currently aware of the link between alcohol and cancer.

AUBREY: In fact, a survey done by the American Society of Clinical Oncology last year found that about 7 in 10 adults did not recognize drinking alcohol as a risk factor for cancer. LoConte says the group is pushing for more education to spread the word and help put the risks in context. She says around the globe, about 5 percent of all cancers are linked to alcohol. The big ones are head and neck cancers as well as liver, colorectal and, in women, breast cancer. LoConte says one way to help people cut back is to help them be more realistic about how much they're actually consuming.

LOCONTE: I think in helping people understand what light drinking is, I think the first thing we need to talk about is what is a drink, right? So that's a single shot, 5 ounces of wine or 12 ounces of beer.

AUBREY: It's really easy to drink more than this without realizing it. Current guidelines recommend no more than one drink a day for women, two for men, but LoConte says even this might be too much.

LOCONTE: I think this study, as I reviewed it, looked like a safer amount would be one drink a day for everybody regardless of gender.

AUBREY: At least that's what this study suggests. More research is underway. Allison Aubrey, NPR News.

(SOUNDBITE OF AXEL KRYGIER'S "POSTCOLOMBINO") Transcript provided by NPR, Copyright NPR.