The evidence is clear: Alcohol can cause cancer.
Earlier this month, US surgeon general Vivek Murthy, MD, issued an advisory,
calling for alcoholic beverages to carry a warning label about cancer
risk. The advisory flagged alcohol as the third leading preventable
cause of cancer in the United States, after tobacco and obesity, and
highlighted people's limited awareness about the relationship between
alcohol and cancer risk.
But, when it comes to cancer risk, are all types of alcohol created equal?
For
many years, red wine seemed to be an outlier, with studies indicating
that, in moderation, it might even be good for you. Red wine has
anti-inflammatory and antioxidant properties — most notably, it contains
the antioxidant resveratrol. Starting in the 1990s, research began to
hint that the compound might protect against heart disease, aging, and
cancer, though much of this work was done in animals or test tubes.
The idea that red wine carries health benefits, however, has been called into question more recently. A recent meta-analysis, for instance, suggests
that many previous studies touting the health benefits of more moderate
drinking were likely biased, potentially leading to "misleading
positive health associations." And one recent study
found that alcohol consumption, largely red wine and beer, at all
levels was linked to an increased risk for cardiovascular disease.
Although wine's health halo is dwindling, there might be an exception: Cancer risk.
Overall,
research shows that even light to moderate drinking increases the risk
for at least seven types of cancer, but when focusing on red wine, in
particular, that risk calculus can look different.
"It's very
complicated and nuanced," said Timothy Rebbeck, PhD, professor of cancer
prevention, Harvard T.H. Chan School of Public Health, Boston. "And
'complicated and nuanced' doesn't work very well in public health
messages."
The Knowns About Alcohol and Cancer Risk
Some
things about the relationship between alcohol and cancer risk are
crystal clear. "There's no question that alcohol is a group 1
carcinogen," Rebbeck said. "Alcohol can cause cancer."
Groups
including the International Agency for Research on Cancer (IARC) and
American Cancer Society agree that alcohol use is an established cause
of seven types of cancer:
Those of the oral cavity, larynx, pharynx, esophagus (squamous cell
carcinoma), liver (hepatocellular carcinoma), breast, and colon/rectum.
Heavy drinking — at least 8 standard drinks a week for women and 15 for
men — and binge drinking — 4 or more drinks in 2 hours for women and 5
or more for men — only amplify that risk. (A "standard" drink has 14 g of alcohol, which translates to a 5-oz glass of wine.)
"We're
most concerned about high-risk drinking — more than 2 drinks a day —
and/or binge drinking," said Noelle LoConte, MD, from the Division of
Hematology, Medical Oncology and Palliative Care, University of
Wisconsin School of Medicine and Public Health, Madison, Wisconsin, who
authored a 2018 statement on alcohol and cancer risk from the American Society of Clinical Oncology (ASCO).
Compared
with not drinking, heavy drinking is linked with a roughly fivefold
increase in the risk for oral cavity, pharyngeal, and esophageal
cancers, and a 61% increase in the risk for breast cancer, according to
LoConte and colleagues.
Things get murkier when it comes to
moderate drinking — defined as up to 1 standard drink per day for women
and 2 per day for men. There is evidence, LoConte said, that moderate
drinking is associated with increased cancer risks, though the magnitude
is generally much less than heavier drinking.
Cancer type also matters. One analysis found that the risk for breast cancer
increased with even light to moderate alcohol consumption. Compared
with no drinking, light to moderate drinking has also been linked to
increased risks for oral cavity, pharynx, larynx, and esophageal
cancers.
As for whether the type of alcoholic beverage matters,
LoConte said, there's no clear physiological reason that wine would be
less risky than beer or liquor. Research indicates that ethanol is the
problematic ingredient: Once ingested, it's metabolized into
acetaldehyde, a DNA-damaging substance that's considered a probable
human carcinogen. Ethanol can also alter circulating levels of estrogens
and androgens, LoConte said, which is thought to drive its association
with breast cancer risk.
"It likely doesn't matter how you choose to get your ethanol," she said. "It's a question of volume."
Hints That Wine Is an Outlier
Still, some studies suggest that how people ingest ethanol could make a difference.
A study published in August in JAMA Network Open
is a case in point. The study found that, among older adults, light to
heavy drinkers had an increased risk of dying from cancer, compared with
occasional drinkers (though the increased risk among light to moderate
drinkers occurred only among people who also had chronic health
conditions, such as diabetes or high blood pressure, or were of lower
socioeconomic status).
Wine drinkers fared differently. Most
notably, drinkers who "preferred" wine — consuming over 80% of total
ethanol from wine — or those who drank only with meals showed a small
reduction in their risk for cancer mortality and all-cause mortality
(hazard ratio [HR], 0.94 for both). The small protective association was
somewhat stronger among people who reported both patterns (HR, 0.88),
especially if they were of lower socioeconomic status (HR, 0.79).
The findings are in line with other research suggesting that wine drinkers may be outliers when it comes to cancer risk. A 2023 meta-analysis
of 26 observational studies, for instance, found no association between
wine consumption and any cancer type, with the caveat that there was
"substantial" heterogeneity among the studies.
This
heterogeneity caveat speaks to the inherent limitations of
observational research, said Tim Stockwell, PhD, from the Canadian
Institute for Substance Use Research, University of Victoria, Victoria,
British Columbia, Canada.
"Individual studies of alcohol and
cancer risk do find differences by type of drink, or patterns of
drinking," Stockwell said. "But it's so hard to unpack the confounding
that goes along with the type of person who's a wine drinker or a beer
drinker or a spirit drinker. The beverage of choice seems to come with a
lot of baggage."
Compared with people who favor beer or liquor,
he noted, wine aficionados are typically higher-income, exercise more
often, smoke less, and have different diets, for example. The "best"
studies, Rebbeck said, try to adjust for those differences, but it's
challenging.
The
authors of the 2023 meta-analysis noted that "many components in wine
could have anticarcinogenic effects" that theoretically could counter
the ill effects of ethanol. Besides resveratrol, which is mainly found
in red wine, the list includes anthocyanins, quercetin, and tannins.
However, the authors also acknowledged that they couldn't account for
whether other lifestyle habits might explain why wine drinkers, overall,
showed no increased cancer risks and sometimes lower risks.
Still, groups such as the IARC and ASCO hold that there is no known "safe" level, or type, of alcohol when it comes to cancer.
In the latest Canadian guidelines
on alcohol use, the scientific panel calculated that people who have 6
drinks a week throughout adulthood (whatever the source of the alcohol)
could shave 11 weeks from their life expectancy, on average, said
Stockwell, who was on the guideline panel. Compare that with heavy
drinking, where 4 drinks a day could rob the average person of 2 or 3
years. "If you're drinking a lot, you could get huge benefits from
cutting down," Stockwell explained. "If you're a moderate drinker, the
benefits would obviously be less."
Stockwell said that choices
around drinking and breast cancer risk, specifically, can be "tough."
Unlike many of the other alcohol-associated cancers, he noted, breast
cancer is common — so even small relative risk increases may be
concerning. Based on a 2020 meta-analysis
of 22 cohort studies, the risk for breast cancer rises by about 10%, on
average, for every 10 g of alcohol a woman drinks per day. This study
also found no evidence that wine is any different from other types of
alcohol.
In real life, the calculus around wine consumption and
cancer risk will probably vary widely from person to person, Rebbeck
said. One woman with a family history of breast cancer might decide that
having wine with dinner isn't worth it. Another with the same family
history might see that glass of wine as a stress reliever and opt to
focus on other ways to reduce her breast cancer risk — by exercising and
maintaining a healthy weight, for example.
"The
bottom line is, in human studies, the data on light to moderate
drinking and cancer are limited and messy, and you can't draw firm
conclusions from them," Rebbeck said. "It probably raises risk in some
people, but we don't know who those people are. And the risk increases
are relatively small."
A Conversation Few Are Having
Even
with many studies highlighting the connection between alcohol
consumption and cancer risk, most people remain unaware about this risk.
A 2023 study
by the National Cancer Institute found that only a minority of US
adults knew that drinking alcohol is linked to increased cancer risk,
and they were much less likely to say that was true of wine: Only 20%
did, vs 31% who said that liquor can boost cancer risk. Meanwhile, 10%
believed that wine helps prevent cancer. Other studies show that even among cancer survivors and patients undergoing active cancer treatment, many drink — often heavily.
"What we know right now is, physicians almost never talk about this," LoConte said.
That
could be due to time constraints, according to Rebbeck, or clinicians'
perceptions that the subject is too complicated and/or their own
confusion about the data. There could also be some "cognitive
dissonance" at play, LoConte noted, because many doctors drink alcohol.
It's
critical, she said, that conversations about drinking habits become
"normalized," and that should include informing patients that alcohol
use is associated with certain cancers. Again, LoConte said, it's
high-risk drinking that's most concerning and where reducing intake could have the biggest impact on cancer risk and other health outcomes.
"From
a cancer prevention standpoint, it's probably best not to drink," she
said. "But people don't make choices based solely on cancer risk. We
don't want to come out with recommendations saying no one should drink. I
don't think the data support that, and people would buck against that
advice."
Rebbeck made a similar point. Even if there's uncertainty
about the risks for a daily glass of wine, he said, people can use that
information to make decisions. "Everybody's preferences and choices are
going to be different," Rebbeck said. "And that's all we can really
do."
