The International Agency for Research on Cancer indicates that alcohol consumption increases the risk of developing at least seven types of cancer, warning that even small amounts may contribute to raising this risk.
Although previous research has linked alcohol consumption to several cancers, including breast, bowel, esophageal, liver, mouth, throat and larynx cancers, researchers from Cambridge University and the Karolinska Institute in Sweden emphasize that most of this evidence is based on observational studies, making it difficult to assert a direct causal relationship.
The new study relied on analyzing genetic factors associated with alcohol consumption using the "Mendelian randomization" technique, which is based on studying genetic variations associated with specific traits in individuals.
The research team analyzed genetic data from approximately 1.4 million people participating in long-term studies in the United Kingdom, the United States, and Finland.
The study results showed a link between genes associated with increased alcohol consumption and the risk of developing cancers of the head, neck, esophagus, and intestines.
As for other types of cancer, including breast cancer, the evidence has been inconsistent or insufficient, suggesting a lack of a clear genetic link, according to Cambridge University.
The study also showed, when focusing on UK data, that predicted alcohol consumption based on genetic factors was associated with a 44% increased risk of death from cancer overall.
Professor Stephen Burgess, a professor of biostatistics at Cambridge University and supervisor of the study, said the results "confirm the harmful effect of alcohol consumption on cancer risk, but suggest that this effect is concentrated in the parts that are directly exposed to alcohol," adding that the study did not find evidence to support the existence of an effect of alcohol consumption on breast cancer risk, contrary to what previous research had concluded.
Dr. Susanna Larsson, an epidemiologist at the Karolinska Institute and the lead analyst, explained that the lack of a clear link with breast cancer may be due to the fact that the real effect is very weak, or to the results of previous studies being affected by other factors, such as the use of hormones, which are difficult to control in observational studies.
Despite these findings, researchers stressed that drinking alcohol, especially excessively, remains harmful to public health, as it increases the risk of heart and liver disease, dementia, as well as violence and suicide.
Commenting on the study, Dr. Clare Knight, director of health information at Cancer Research UK, said there is "strong, accumulating evidence over decades linking alcohol to a number of cancers, including breast cancer."
She added that even small amounts of alcohol can damage body cells, noting the importance of placing clear warning labels on alcohol containers to raise awareness and encourage people to think about how much they consume.
Sally Koom, deputy director of nursing and health information at Breast Cancer Now, confirmed that the risk of developing breast cancer is affected by multiple factors, including genetics, lifestyle and environment, and that it is impossible to say for certain why anyone develops the disease.
She added that the study, while indicating the absence of a direct effect of alcohol on breast cancer, does not rule out a possible link supported by other studies, stressing the need for further research and reiterating the recommendation to limit alcohol consumption and follow a healthy lifestyle.
The study was published in the journal BMC Medicine.
