The study found that people who increased the amount they drank had a higher risk of all cancers, including alcohol-related cancers, than the group that made no changes to their drinking habits.
The risk also increased for non-drinkers who changed their habits and became mild, moderate or heavy drinkers.
“This is another great example of how changing behavior could significantly decrease cancer deaths,” Dr. William Dahut, chief scientific officer at the American Cancer Society, told CNN in an email. “The most striking findings is the impact on cancer deaths with changes in alcohol consumption. Individuals should be strongly counseled that they can dramatically decrease their cancer risk if alcohol consumption is moderated.”
The study looked at data from more than 4.5 million participants. The study participants were from the Korean National Health Insurance Service, were 40 years old and up, had taken part in a national health screening in 2009 and 2011, and had available data on their drinking status.
“In this large cohort study that used repeated measures of alcohol consumption, we found that individuals who increased their alcohol consumption, regardless of their baseline drinking level, had an increased incidence of alcohol-related and all cancers compared with those who sustained their current level of drinking,” wrote the study authors from the Seoul National University Hospital. “Quitting was not associated with a lower incidence of alcohol related cancer, but if abstinence was maintained over time, the incidence of alcohol-related and all cancers tended to decrease.”
In those who increased their drinking from being non-drinkers, the researchers found a high incidence of stomach, liver, gallbladder and lung cancer, multiple myeloma and leukemia.
They also found that there was an association between decreased risk of alcohol-related and all cancers and reducing heavy drinking to moderate or mild levels of drinking.
Although the study has key strengths, such as the size of the cohort and the large number of cases, it also has some limitations, according to an accompanying editorial from experts at the National Cancer Institute.
First, the two assessments of alcohol use took place two years apart with a maximum follow-up of seven years and the authors did not have details about participants’ alcohol intake earlier in life, meaning they couldn’t examine long-term changes.
It also lacked information on other healthy behaviors that could have happened alongside reductions in alcohol intake, so the changes in risk may not be attributed solely to alcohol use.
There was also no discussion about alcohol-induced flushing and an inherited deficiency in an enzyme involved in breaking down alcohol, which are common in East Asian populations. The editorial authors said that further research in other racial and ethnic groups is needed.
Despite the limitations, the editorial authors said the research provides “important, new findings about the potential role of changes in alcohol consumption in cancer risk,” and suggest future studies follow its lead and examine the association in other populations and using longer intervals between assessments.
The American Cancer Society calls alcohol use “one of the most important preventable risk factors for cancer, along with tobacco use and excess body weight.”
The organization says that drinking accounts for around 6% of all cancers and 4% of all cancer deaths in the US.
According to ACS and the US Centers for Disease Control and Prevention, drinking alcohol can increase the risk of six types of cancer: mouth and throat, larynx, esophagus, colon and rectum, liver and breast in women.
ACS also says that alcohol use probably increases the risk of stomach cancer and some others.
“For each of these cancers, the more alcohol you drink, the higher your cancer risk,” ACS say. “But for some types of cancer, most notably breast cancer, consuming even small amounts of alcohol can increase risk.”
“I think it’s very important that folks realize that heavy alcohol use can significantly increase the risk of cancer,” said Dahut. “Unfortunately, although this is not a new finding, this information would be very surprising to many. It is imperative that physicians inform patients of this risk and provide whatever tools are necessary to help patients modify this behavior.”