Increased cancer risk is often associated with smoking, obesity, and UV radiation, but the role of alcohol remains largely overlooked. However, the International Agency for Research on Cancer (IARC) has classified alcoholic beverages – and the ethanol within them – as Group 1 Carcinogens, meaning they are known to cause cancer in humans (Figure 1). This classification reflects the strong evidence that alcohol consumption contributes to many types of cancer, including breast, colorectal, and liver cancers in humans. Despite its widespread consumption, alcohol poses a significant, often modifiable risk for cancer development. In this article, we’ll explore how alcohol acts as a carcinogen and why reducing its intake could play a crucial role in cancer prevention.
The Alcohol-Cancer Link at a Glance
According to the World Health Organization (WHO), alcohol is responsible for approximately 4% of all cancer cases worldwide. In 2020, over 740,000 cancer cases globally were attributed to alcohol consumption. Research demonstrates that there is no safe level of alcohol consumption when it comes to cancer prevention. The less alcohol your drink, the lower your cancer risk.
This risk is further amplified when alcohol consumption is combined with tobacco use, as illustrated in Figure 2.
Below are findings from recent research on alcohol’s effects on specific cancer risks:
Breast Cancer
Breast cancer is most common cancer linked to alcohol in women and in 2020, it was the third largest contributor of alcohol-causing cancer cases globally.
Alcohol primarily increases the risk of hormone-driven breast cancers (ER+ and PR+).
A meta-analysis showed no significant impact of alcohol on hormone-negative breast cancers (ER-/PR-).
Colorectal Cancer
Alcohol’s impact on gut health and chronic inflammation contributes to an increased risk of colorectal cancer, especially among moderate to heavy drinkers.
Light drinking does not appear to significantly increase colorectal cancer risk.
Liver Cancer
Long-term heavy drinking leads to liver damage and liver disease, increasing the risk of hepatocellular carcinoma (HCC), the most common type of liver cancer.
A 14% increase risk per 10 g/day of alcohol consumption has been observed up to 45 g/day. Heavy drinkers face double the risk.
Mouth and Throat Cancers
Alcohol increases the risk of cancers in the oral cavity, pharynx, and larynx, particularly in individuals who also smoke.
A 15% increased risk of mouth cancer was observed with 10 g/day of alcohol consumption. Moderate and heavy drinkers are at higher risk for pharyngeal and laryngeal cancers.
Esophageal Cancer
Alcohol increases the risk of esophageal squamous cell carcinoma, with greater risks observed in Asian populations compared to those in North America or Europe, suggesting potential genetic factors.
Stomach Cancer
Heavy alcohol consumption increases the risk of stomach cancer by 21%, with no significant risk observed for light or moderate drinkers.
What Happens to our Bodies when we Drink Alcohol?
Alcohol disrupts the body’s natural functions through a variety of different mechanisms, some of which are still unknown. However, research has shown that most mechanisms are linked to how alcohol, as ethanol, is metabolised. Here are some of the ways alcohol contributes to cancer risk:
Acetaldehyde: when alcohol is metabolised, it is converted into a compound called acetaldehyde. Acetaldehyde is a toxic substance that damages DNA and interferes with the body’s ability to make new DNA and repair DNA damage. This process increases the likelihood of genetic mutations that lead to cancer.
Estrogen levels: Alcohol consumption causes an increase in estrogen and estradiol levels in the blood. An excess of these hormones can stimulate the growth of estrogen-sensitive breast cancer cells, increasing the risk of breast cancer.
Oxidative Stress and Inflammation: long-term alcohol use can lead to oxidative stress, an imbalance between unstable molecules (called free radicals) and antioxidants (neutralize the free radicals). Oxidative stress can lead to inflammation, creating an ideal environment for cancer cells to grow and develop.
Nutritional and Immune Deficiencies: excessive drinking depletes vital nutrients like folate. Folate is a vitamin that is important for DNA damage repair. Additionally, increased alcohol consumption weakens the immune system, reducing its ability to identify and eliminate potentially cancerous cells and defend against diseases and infection.
Moderation Matters
For many, alcohol is an integral part of social life – a glass of wine with dinner or a couple of cold beers on a sunny day feels harmless. However, even "a couple shots on the weekend" can significantly impact your health. Alcohol consumption, even within recommended limits, can increase the risk of cancer and other health issues such as liver disease and cardiovascular disease. For optimal health, individuals who choose to drink should do so in moderation, keeping their intake within dietary guidelines while being mindful of associated risks.
For more information on carcinogens and preventative measures, check out the IARC’s comprehensive infographic, Human Cancer: Known Causes and Prevention by Organ Site!
References
American Cancer Society. Known and probably human carcinogens: https://www.cancer.org/cancer/risk-prevention/understanding-cancer-risk/known-and-probable-human-carcinogens.html
Canadian Cancer Society. Some sobering facts about alcohol and cancer risk: https://cancer.ca/en/cancer-information/reduce-your-risk/limit-alcohol/some-sobering-facts-about-alcohol-and-cancer-risk
Figures 2 though 5 were adapted from https://www.hhs.gov/surgeongeneral/priorities/alcohol-cancer/index.html. Created using Biorender.com.
Halsted, C., Villanueva, J., Devlin, A., Chandler, C. Metabolic interactions of alcohol and folate. https://pubmed.ncbi.nlm.nih.gov/12163694/
Rumgay, H., Murphy, N., Ferrari, P., Soerjomataram, I. Alcohol and Cancer: Epidemiology and Biological Mechanism. https://pmc.ncbi.nlm.nih.gov/articles/pmid/34579050/
World Health Organization. 5 Facts About Alcohol & Cancer. https://www.who.int/docs/librariesprovider2/default-document-library/alcohol-and-cancer-factsheet-eng.pdf
Assessed and Endorsed by the MedReport Medical Review Board