17/11/2016 07:30 GMT | Updated 17/11/2017 05:12 GMT

Alcohol - How Does It Give Us Cancer?

From sipping merlot in Bordeaux to clinking steins of beer in Munich to warming up with vodka in Russia, drinking alcohol is an ingrained part of many cultures worldwide. England is no exception, with more than 10 million people drinking more then the recommended daily alcohol limit. A worrying 43% of Brits aren't aware that these drinking habits are increasing their cancer risk.

Research by World Cancer Research Fund shows that drinking alcohol is linked to an increased risk of several cancers: bowel, breast, mouth and throat, oesophageal, stomach and liver. In the UK, 21,000 cases of cancer could be prevented each year if nobody drank alcohol, but how does alcohol actually interact with us to cause such a drastic effect?


How alcohol increases cancer risk

Nobody is completely sure exactly how alcohol interacts with our bodies to increase the likelihood of cancer forming, but there are some strong theories about how this could work.

Alcohol is converted to a toxic substance that damages DNA

Alcohol that we drink contains ethanol, which has been found to be carcinogenic. When we drink ethanol, it is converted by an enzyme in our cells into a toxic substance, acetaldehyde. Usually acetaldehyde is converted by other enzymes (known as aldehyde dehydrogenase) into acetate, which is useful for the cells to make energy. However, when there is a large amount of alcohol entering the body, there is more acetaldehyde than the enzymes can process, causing a build up of acetaldehyde. This can be dangerous because acetaldehyde can directly damage DNA, affecting how the DNA functions and its ability to repair itself, which can lead to the cells becoming cancerous.

So the more we drink, the more toxic acetaldehyde builds up, the more DNA damage occurs and the more the cancer risk increases.

But it's not just heavy drinkers who are at risk. Bacteria found in the mouth are particularly good at converting ethanol into the toxic acetaldehyde, which can give you a build-up of acetaldehyde even if you've only been drinking smaller amounts.

Alcohol can reduce folate absorption

Folate is a vitamin found in a variety of different foods such as dark green vegetables and legumes. It helps to control how the 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. Absorbing less folate can remove this 'off' switch mechanism, which can result in big changes in cells, potentially in ways that can make a cell more likely to become cancerous.

Alcohol could allow more dangerous molecules entry into cells

Another theory is that alcohol could physically help carry other cancer-causing substances into cells. This means that alcohol can act as a solution that carcinogens can mix with to help them sneak into cells.

Ideas specific to cancer type

There are also some explanations of how drinking alcohol can lead to specific cancer types. For breast cancer, the most common cancer in women in the UK, there is an idea that alcohol can affect hormone levels in women, causing oestrogen levels to rise, which could help cancer cells to grow. This may help explain why 11,700 cases of breast cancer could be prevented in the UK each year if nobody drank alcohol. However many factors can affect oestrogen levels, so this explanation isn't that straightforward.

Another example of this is that drinking excess alcohol can cause liver cirrhosis, which can make liver cancer much more likely.

What next?

It is evident that there are many ways in which alcohol can do some real damage but more work needs to be done to pin down exactly how drinking alcohol can have a cancer-causing effect. To help fill the gaps in our knowledge about how alcohol and other lifestyle factors affect cancer risk, World Cancer Research Fund is developing and testing a groundbreaking new method to work this out.

So, it may be a difficult choice to leave the drinks on the shelf, but our bodies will thank us in the long term.