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Two genetic variants reduce cancer-causing effects of alcohol

by Ed Yong | Analysis

27 May 2008

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Alcohol causes cancerThe ways that our genes and our lifestyle choices interact to affect our risk of cancer is one of the most fascinating areas of research in cancer prevention. But it’s all still a bit of a grey area. So most health messages tend to be very broad and general – simply because the evidence they are based on comes from studies of large groups of genetically diverse people.

But this is starting to change, as studies get more sophisticated. For example, a new piece of research published this week in Nature Genetics identifies two rare versions of the genes ADH1B and ADH7 that can lessen the harmful effects of alcohol in causing cancer in people who carry them.

Both ADH1B and ADH7 belong to a group of seven genes that help us to break down alcohol. Some people seem to carry rare versions of these genes that are exceptionally good at their jobs.

For example, about 1-2 per cent of the British population have a version of ADH1B that allows them to metabolise alcohol up to a hundred times faster than people who carry the gene’s more common versions.

We’ve known for a long time that alcohol causes seven types of cancer. In addition to smoking, it is one of the most important causes of cancers of the mouth, larynx (voice box) and oesophagus (food pipe). But according to this new research, some people are less vulnerable to the cancer-causing effects of alcohol than others.

The research was led by Paul Brennan from the International Agency for Research into Cancer. Together with an international team of scientists, he compared the sequences of both genes in 3,800 people with cancer and 5,200 healthy people.

Brennan’s study showed that people with the rare variants were less likely to get cancers of the mouth, larynx (voice box) and oesophagus (food pipe) than people with the common versions.

The genes have no bearing on a tee-totaller’s risk of cancer. After all, given that they affect the way the body copes with alcohol, you would expect that they wouldn’t have any effect in people who don’t touch the stuff.

However, heavy drinkers were less likely to get mouth, laryngeal or oesophageal cancer if they had the rare version of the gene.

The key point here is that people with these rare versions cannot reduce their risk of certain cancers by drinking alcohol. Alcohol still increases their risk of cancer, but to a lesser degree than their peers who carry the common genetic variants.

We know through a large amount of research that drinking even small amounts of alcohol can increase the risk of several cancers. These include breast, bowel, mouth, oesophageal, laryngeal and liver cancers.

So if you’re concerned about alcohol, we have developed an online gadget (see below) that allows you to easily keep track of how much you drink. Just enter your drinks every day and the gadget will tell you how that works out in terms of units and calories, and it’ll then plot the numbers on a simple graph. You can also test your knowledge about alcohol and cancer with our online quiz.