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The Sobering Truth: Alcohol as a Carcinogen

Updated: Feb 22


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 strong evidence that alcohol consumption contributes to many types of cancer, including breast, colorectal, liver, and esophageal cancers. Despite its widespread consumption, alcohol poses a significant, often modifiable risk for cancer development. In this article, we explore how alcohol acts as a carcinogen and why reducing its intake could play a crucial role in cancer prevention.


Figure 1. IARC Classifications of Carcinogens. (Taken from https://www.compoundchem.com/2023/07/14/carcinogens/)
Figure 1. IARC Classifications of Carcinogens. (Taken from https://www.compoundchem.com/2023/07/14/carcinogens/)

The Alcohol-Cancer Link at a Glance


According to the World Health Organization (WHO), alcohol is responsible for approximately 4% of all cancer cases in the European Region and other sources say similar numbers are reported 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 amount of alcohol you drink directly affects your cancer risk.


This risk is further amplified when alcohol consumption is combined with tobacco use, as illustrated in Figure 2.

Figure 2. How Alcohol Facilitates Carcinogen Absorption
Figure 2. How Alcohol Facilitates Carcinogen Absorption

Below are findings from recent research on alcohol’s effects on specific cancer risks:

  1. Breast Cancer

    • Breast cancer is the most common cancer linked to alcohol in women. In 2020, it was the largest contributor of alcohol-related 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.

    • Even light drinking appears to increase colorectal cancer risk, though the effect is smaller compared to heavier drinking.

    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% increased 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 certain populations (e.g., Eastern Asia) 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 metabolized, it is converted into a compound called acetaldehyde, a toxic substance that damages DNA and interferes with the body's ability to repair DNA. This process increases the likelihood of genetic mutations that lead to cancer.


Figure 3. Ethanol, Acetaldehyde, and DNA Damage
Figure 3. Ethanol, Acetaldehyde, and DNA Damage

Estrogen levels: Alcohol consumption increases estrogen and estradiol levels in the blood, stimulating the growth of estrogen-sensitive breast cancer cells and increasing the risk of breast cancer.


Figure 4. Long-term Increased Estrogen levels can lead to DNA Damage
Figure 4. Long-term Increased Estrogen levels can lead to DNA Damage

Oxidative Stress and Inflammation: Long-term alcohol use leads to oxidative stress, an imbalance between free radicals and antioxidants. This creates an environment conducive to cancer cell growth and development..

Figure 5. How Reactive Oxygen Species leads to DNA, Protein and Lipid (Fat) Damage
Figure 5. How Reactive Oxygen Species leads to DNA, Protein and Lipid (Fat) Damage

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 (may be suitable for advanced readers only)!

 


References



Alcohol and Cancer: Epidemiology and Biological mechanisms https://pubmed.ncbi.nlm.nih.gov/34579050/




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/




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