How does alcohol increase cancer risk?

A tray of alcoholic drinks

Lucy EcclesLucy Eccles has a background in biomedical science and is currently International Communications Officer at World Cancer Research Fund.

For some people, our recommendation on limiting how much alcohol to drink can be the hardest one to swallow. 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.

Globally the amount of alcohol consumed in 2010, was equal to 620 measures of whiskey, or 310 glasses of red wine per person over the age of 15, and Eastern Europeans drank more alcohol than any other part of the world. These habits could be putting huge numbers of us at risk.

World Cancer Research Fund International’s global analysis of research shows that drinking alcohol is linked to an increased risk of several cancers: bowelbreast, mouth and throatoesophageal, and liver. But how does alcohol actually interact with us to cause such a drastic effect?

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

Alcohol 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 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 affects the way DNA works, in most cases acting as an ‘off’ switch for 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 the cell, potentially in ways that can make a cell more likely to become cancerous.

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. One example of this is that drinking excess alcohol can cause liver cirrhosis, which can make liver cancer much more likely. For breast cancer there is an idea that alcohol can affect hormone levels in women, causing oestrogen levels to rise, which could help cancer cells to grow. However, many factors can affect oestrogen levels, so this explanation isn’t that straightforward.

It is clear more work needs to be done to pin down the exact mechanisms, but what is evident is there are many ways by which alcohol can really do some damage. To help fill the gaps in our knowledge about how alcohol and other lifestyle factors affect cancer risk, we are developing and testing a groundbreaking new method to work this out.  This method will allow us to systematically review mechanistic studies related to diet, nutrition, physical activity and cancers in a robust, standardised way.

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

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