A new study suggests that even light-to-moderate alcohol consumption may increase overall cancer risk, compared with not drinking any alcohol at all.
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The research, which was conducted in Japan, found that current and former drinkers were at an 18% higher overall risk for cancer compared with non-drinkers and that the overall risk was lowest at zero alcohol consumption.
Given the current burden of overall cancer incidence, we should further encourage promoting public education about alcohol-related cancer risk."
Study author Masayoshi Zaitsu, University of Tokyo and the Harvard T.H. Chan School of Public Health in Boston
Previous studies have raised concerns
Although previous research has linked light alcohol drinking with a decreased risk for certain cancers, others have suggested that light-to-moderate consumption is associated with a higher risk for cancer overall.
"Recent studies have raised concerns about the risk of even light to moderate levels of alcohol consumption for cancer incidence," writes Zaitsu and team.
To investigate, the researchers assessed 2005 to 2016 clinical data from 33 general hospitals located in Japan. They compared the drinking habits of 63,232 patients with cancer and an equal number of healthy controls matched for gender, age, hospital admission date, and admitting hospital.
All participants self-reported their average daily alcohol intake and how many years they had been drinking. One standardized drink was defined as a six-ounce cup of Japanese sake, a 17-ounce bottle of beer, a six-ounce glass of wine, or a two-ounce glass of whiskey.
Cancer risk was lowest at zero alcohol consumption
After adjusting for smoking status, hypertension, diabetes, obesity, and other confounding variables, the team found that the overall cancer risk was lowest at zero alcohol consumption.
Light alcohol consumption at a 10-year-drink point (such as one drink per day for ten years or two drinks per day for five years) increased the overall risk for cancer by 5%.
Among people who consumed two drinks per day for 40 years, the relative risk for having any cancer increased by 54%, compared with zero consumption.
The increased risk appeared to be accounted for by alcohol-associated cancer risk across relatively common sites, including the colon, stomach, breast, prostate, and esophagus.
Compared with non-drinkers, the risk for colon and liver cancer was 30% higher among drinkers, and the risk for stomach and breast cancer was more than 20% higher.
Current and former drinkers also had a four-fold increased risk of developing esophageal cancer and a two-fold increased risk of developing cancer of the larynx.
Cancer is the number one killer in Japan
Zaitsu says cancer is the leading cause of death in Japan. In the United States, it is the second leading cause of death after heart disease.
"The current national cancer control strategy needs to strengthen the emphasis on moderating drinking behavior in the Japanese population to reduce the burden of cancer incidence," writes the team.
The authors say certain limitations of the study should be noted. Data on drinking habits were self-reported, which is not always reliable, and the team was unable to control for diet, physical activity, and family history of cancer. Furthermore, Japanese people have a higher prevalence of genetic variations in the enzyme aldehyde dehydrogenase 2, which slows their metabolism of alcohol. This means the findings may not be generalizable to other populations.
In conclusion, Zaitsu says that consuming one alcoholic drink per day is "probably not a big problem."
However, "drinking too much over long periods of time might be dangerous. We enjoy drinking, but we need to think about it," he concludes.
Zaitsu, M. et al. (2019) Light to moderate amount of lifetime alcohol consumption and risk of cancer in Japan. Cancer. DOI: https://doi.org/10.1002/cncr.32590