How alcohol causes cancer

Alcohol consumption is estimated to be responsible for approximately 3% of cancers (i.e. nearly 3,500 cases) newly diagnosed in Australia each year.

Alcohol is a known carcinogen. This means that alcohol causes cancer.

There is strong evidence that drinking alcohol increases the risk of at least seven types of cancer including female breast, liver, mouth, throat (pharynx and larynx), oesophagus and bowel. Drinking alcohol may also increase the risk of stomach cancer.

Other factors including smoking, being above a healthy weight, poor oral hygiene and poor diet may also increase the risk of cancers, particularly when combined with regular drinking.

For example, if you smoke and drink, the risk of a cancer developing is significantly greater than each of these risk factors on their own.

Ways alcohol cause cancer

Alcohol can cause cancer by:

  • ethanol (pure alcohol) being broken down by the body becomes a toxic chemical called acetaldehyde, which can damage cells if it bonds with DNA, causing cells to be replicated incorrectly
  • influencing hormone levels, which can modify how cells grow and divide
  • direct tissue damage, increasing the absorption of other carcinogens.

Acetaldehyde

Acetaldehyde is toxic and can lead to irreversible DNA damage, which can lead to cancer. 

  1. When alcohol is consumed, the mouth and stomach convert a small amount of ethanol (pure alcohol) to acetaldehyde.
  2. The liver converts most of the remaining ethanol to acetaldehyde.
  3. The liver then converts acetaldehyde to acetate, an energy the body can use.
  4. If too much alcohol is consumed (more than 1.8 standard drinks), the body can't process the acetaldehyde fast enough.
  5. Acetaldehyde then builds up in the body. 

Hormones

Consuming a large amount of alcohol can cause circulating oestrogen levels to rise, leading to three things:

  1. Altered structural development of mammary glands.
  2. Increased mammary DNA damage.
  3. Stimulated proliferation and migration of cells.

These hormone changes can cause breast cancer in women.

The changes may also affect some trans and gender diverse people in terms of their cancer risk. Please talk with your GP or gender specialist for personalised advice.

Absorption

Consuming a large amount of alcohol alters the cells in the mouth and throat (pharynx, larynx).

Alcohol can act as a solvent, making it easier for other carcinogens such as tobacco to be absorbed into cells.

This alteration allows other carcinogens to be more easily absorbed and can lead to cancers of the mouth and throat.