What is alcohol 

The alcohol found in all alcoholic drinks is called ethanol, which is made when grain, fruits and vegetables undergo a process called fermentation​. It is this compound that gives the feeling of being ‘’drunk’. 

This feeling happens when the ethanol molecules pass through the gaps between brain cells and interfere with the brain’s activities. 

Alcohol and alcoholic drinks are classified as a group 1 carcinogen by the International Agency for Research on Cancer (IARC) since 1988​. This means they are known to cause cancer in humans. 

Alcohol guidelines and units 

Different alcoholic drinks contain different amounts of alcohol. This depends on the amount of time it ferments​.  

The amount of alcohol in a drink is measured in units, with 1 unit equalling 10ml or 8g of pure alcohol (ethanol) found within that drink​.  

Alcoholic drinks are often also labelled with a percentage, followed by the abbreviation ‘ABV’. This stands for Alcohol By Volume. This number is the amount of alcohol in that drink​.  

Examples of percentage ABV, units and calories for some alcoholic drinks can be seen in the table below: 

The UK Guidelines on drinking alcohol recommend no more than 14 units of alcohol per week, spread across at least 3 days, with some alcohol-free days in between​. 

Alcohol and cancer 

Drinking alcohol is strongly linked to seven different types of cancer: mouth, throat, larynx, oesophagus, bowel, liver and is a significant risk factor for breast cancer​. 

All types of alcohol increase the risk of cancer as it is the alcohol itself that causes the damage​. 

In 2020, an estimated 4.1% of all new cancer cases worldwide were attributed to drinking alcohol​. 

In the UK, an estimated 3.3% of cancer cases in 2015 were related to drinking alcohol​. 

 Alcohol consumption and breast cancer risk 

Drinking alcohol increases the risk of pre- and post-menopausal breast cancer in women. 

Scientific studies have shown that as the amount of alcohol you drink increases, so does your risk of breast cancer. Importantly, there is no lower threshold or safe limit for drinking alcohol when it comes to breast cancer risk​. Even very light drinking (≤1 standard drink/week) increases risk.  

In the UK, it is estimated that 8% (around 4,400) of female breast cancer cases are linked to alcohol consumption (based on data from 2015)​. 

Compared to non-drinkers, breast cancer risk has been found to be 9% higher in women who drink up to 2 units of alcohol per day, and 60% higher for women who drink 6 or more units per day. 

Several studies have found that alcohol consumption is mostly linked to the development of hormone receptor-positive breast cancer​. 

Some evidence suggests that binge drinking (more than 6 units or 4 drinks in a short period) may result in a higher breast cancer risk, particularly for pre-menopausal women.  

For men, the link between alcohol isn’t clear. Some evidence suggests heavy drinking (>7.5 units/day) may increase a man’s breast cancer risk. However, scientists do not fully understand why this might be the case​. 

How does alcohol increase the risk of developing female breast cancer?  

The exact way alcohol increases a woman’s risk of breast cancer isn’t fully known, but scientists believe it’s due to some or all of the following reasons: 

• Alcohol raises the levels of circulating hormones such as oestrogen, which can increase the number of times a cell divides. High levels of oestrogen are known to increase breast cancer risk. 

• In the liver and breast tissue, alcohol is broken down to acetaldehyde, a chemical compound that can cause cancer by damaging cells and preventing their repair. 

• Alcohol can damage the DNA inside the cell’s energy centres (mitochondria) and cause stress to the cells. Over time, this damages healthy cells and raises the risk of breast cancer. 

• Alcohol may negatively affect the levels of certain vitamins and nutrients in the body, which are important in producing DNA in cells.  

• Alcohol can promote weight gain, increasing the breast cancer risk for post-menopausal women and men. 

• Alcohol may also influence or interact with other known breast cancer risk factors, such as breast density ​and benign (non-cancerous) breast disease which may increase overall risk.  

Can lowering alcohol intake reduce breast cancer risk 

There is no safe level for drinking alcohol when it comes to your breast cancer risk. This means that any amount of alcohol consumed can increase your breast cancer risk. 

If you do drink, it is important to keep to the current UK guidelines of no more than 14 units a week. This should be spread over at least three days and have several alcohol-free days in between. 

Further reading  

For more details, please see our alcohol and breast cancer review 

For further tips, read our blog on how to cut down on alcohol and why it matters 

You can also download our FREE Ditch the Drink recipe eBook here  

If you need further support regarding alcohol, contact your GP, who will be able to provide confidential advice and support.