Not everyone who consumes alcohol develop cancers. However, scientists have found that some cancers are more frequent in people who drink more alcohol than others.
The International Agency for Research into Cancer (IARC), which is a part of the World Health Organization, has classified alcohol as a Group 1 carcinogen as of 1988. IARC's rulings are the gold standard in terms of determining if something induces cancer, and Group 1 is their highest risk category. It means that there is authentic evidence that alcohol causes cancer in humans. More modernistic reviews by IARC and other agencies have also concluded that drinking alcohol is the basis for cancer.
Facts related to alcohol causing cancer:
A study released in 2018 found that drinking too much alcohol causes 3% of cancer cases in the UK, i.e., around 11,900 cases each year. The proportion of cases down to alcohol was maximum for mouth and upper throat (pharynx) cancers (more than a third), but breast cancer accounted for the most extensive overall number of cases linked to alcohol (around 4,400 cases each year)1.
An analysis of the evidence in 2012 concluded that having 1 drink a day (around 1.5 units) could escalate the risk of breast cancer by 5%2.
Alcohol boosts the risk of cancers of the mouth, pharynx (upper throat), larynx (voice box) and esophagus(gullet or food pipe)3.
An audit in 2014 estimated that people who drink more than 3 drinks per day (where one drink has around 1.5 units of alcohol) raised their risk of liver cancer by 16%4.
A review of 61 surveys found that the danger went up the more alcohol people drank, and the heaviest drinkers' (four drinks a day or more) risk went up by about half5.
Alcohol is also associated with bowel cancer.
The possible mechanisms due to which alcohol accounts for cancer:
Alcohol leads to the formation of a toxin called acetaldehyde in the body. It gets accumulated in the body and cripples the DNA (Deoxyribonucleic acid). It also constrains the repair of the damaged DNA (Deoxyribonucleic acid) and leads to cancer6.
Excessive consumption of alcohol leads to alcoholic liver diseases and liver cirrhosis, which is the complete damage of the liver. This leads to liver cancer7.
Alcohol increases the concentration of steroids in the body, notably estrogen leading to breast cancer. Increased estrogen is one of the important risk factors for breast cancer8.
It also prevents folate metabolism and decreases the levels of folate in the body. Folate is essential for the evolution of DNA (Deoxyribonucleic acid) and repair of damaged DNA (Deoxyribonucleic acid).
Alcohol leads to formation and build-up of reactive oxygen free radical species, especially in the liver. They also contribute to the damage of DNA (Deoxyribonucleic acid) and thus lead to cancer9.
In conclusion, alcohol is found to have a direct association with head and neck cancers, breast cancer, esophageal cancer and liver cancer. The risk of cancer is directly dependent on the amount of alcohol consumed. This risk can be mitigated entirely if alcohol consumption is stopped before the cancers develop.
Seitz, H., et al., Epidemiology and pathophysiology of alcohol and breast cancer: Update 2012. Alcohol and Alcoholism, 2012.
Corrao, G., et al., A meta-analysis of alcohol consumption and the risk of 15 diseases. Prev Med, 2004;38(5):613-9
Turati F, Galeone C, Rota M, et al. Alcohol and liver cancer: a systematic review and meta-analysis of prospective studies. Ann Oncol. 2014;25(8):1526-1535.
Fedirko, V., et al., Alcohol drinking and colorectal cancer risk: an overall and dose-response meta-analysis of published studies. Annal Oncol, 2011;22(9):1958-72.
International Agency for Research on Cancer. Consumption of alcoholic beverages. IARC Monogr Eval Carcinog Risks to Humans. 2012;100E.
Sidharthan S, Kottilil S. Mechanisms of alcohol-induced hepatocellular carcinoma. Hepatol Int. 2014;8(2):452-457
Rinaldi AS, Peeters PHM, Bezemer ID, et al. Relationship of Alcohol Intake and Sex Steroid Concentrations in Blood in Pre- and Post- Menopausal Women: The European Prospective Investigation into Cancer and Nutrition. Cancer Causes and Control. 2006;17(8):1033-43.
Boffetta P, Hashibe M. Alcohol and cancer. Lancet Oncol. 2006;7(2):149-156.