Alcohol – how does it increase breast cancer risk?

16 November 2016 | Science and research

Lucy is the former Press and Communications Officer at World Cancer Research Fund.

However, research by World Cancer Research Fund shows that drinking alcohol is linked to an increased risk of several cancers, including breast cancer. In the UK, around 11,700 cases of breast cancer could be prevented each year if nobody drank alcohol.

So how might alcohol interact with our bodies to increase the likelihood of breast cancer forming?


Alcohol that we drink contains ethanol, which is converted in our bodies into a toxic substance called acetaldehyde. Usually acetaldehyde is converted into acetate, which can be used by the cells for energy. However, when there is more acetaldehyde than can be processed, a potentially dangerous build-up occurs. 

Too much acetaldehyde can directly damage DNA, which, in turn, can lead to cancerous cells. The more we drink, the more toxic acetaldehyde builds up, the more DNA damage occurs and the more our cancer risk increases.

And it’s not just heavy drinkers who are at risk – bacteria found in the mouth are particularly good at making acetaldehyde, which can lead to a build-up even if you’ve only been drinking small amounts.

Lack of folate

Folate is a vitamin found in a variety of different foods such as green vegetables. It helps to control how our DNA works, in most cases acting as a control mechanism by ‘switching off’ particular genes.

Drinking too much alcohol can reduce how much folate we absorb in the liver, potentially removing this ‘off switch’ mechanism. This can result in big changes in cells, potentially in ways that can make a cell more likely to become cancerous.

Alcohol and breast cancer infographic

Alcohol as a carrier

It’s also possible that alcohol helps carry cancer-causing substances called carcinogens around the body. Some scientists believe that, by mixing with alcohol, carcinogens are more able to sneak into cells – like the Trojan Horse, and just as dangerous.

Excess oestrogen

Another theory is that alcohol causes oestrogen levels to rise in women, which can help breast cancer cells to grow. However, many factors can affect oestrogen levels, so this explanation isn’t straightforward.

So while we’re still not sure exactly how alcohol increases cancer risk, we do know for sure that alcohol does increase cancer risk.

It may be a difficult choice to leave the drinks on the shelf, but we can be certain that our bodies will thank us for it in the long term.

It’s Alcohol Awareness Week – what better time to check out our tips on how to drink less?

Lucy Eccles | 16 November 2016