Alcohol and cancer: the evidence

International health organisations like the World Health Organisation agree that alcohol can cause a range of cancers. 1,2,3,4 This is based on the consistent results of many different studies all around the world. 4 This page will tell you about why we think alcohol is a risk factor for cancer.

The Oxford Textbook of Medicine estimates that 6% of cancer deaths in the UK are caused by alcohol. And all of these deaths could be avoided. 5

Aside from smoking, alcohol is the most important cause of mouth and foodpipe cancers.

One review of many studies found that people who drink 6 units a day have triple the risk of mouth cancer and double the risk of oesophageal cancer, compared to non-drinkers. 6 That’s the same as two pints of premium lager or three standard glasses of wine.

The International Agency for Cancer Research says that heavy drinking increases the risks of these cancers by 5 to 10 times. 4 But even light drinking (just three units a day) can increase the risk of mouth cancer. 6

Alcohol is one of the main risk factors for liver cancer. 7 Heavy drinking can lead to cirrhosis, a condition where the liver is repeatedly damaged and scar tissue builds up. Cirrhosis increases the risk of liver cancer.

And the risks of liver cancer are even greater if a person is infected with the hepatitis B or C viruses. One in five people with these viruses develop cirrhosis and liver cancer. People with these infections should avoid alcohol, as even small amounts could damage their livers. 8

Even small amounts of alcohol can increase your risk of breast cancer. Several studies have found that every alcohol unit drunk a day increases the risk of breast cancer risk by about 7-11%. 9,10,11,12

There is unlikely to be a safe level of alcohol which doesn’t increase the risk of breast cancer. Some studies have found that drinking just one unit a day can increase a woman’s chances of developing breast cancer. 13

Studies have recently shown that alcohol can increase the risk of bowel cancer and even small amounts can have an effect. The EPIC study found that for every 2 units a person drinks each day (less than a pint of premium lager) their risk of bowel cancer goes up by 8%. 14

Tobacco also causes mouth, oesophageal and liver cancers but scientists have found the effects of alcohol and tobacco together are much worse.

One study found that the risk of liver cancer was ten times greater in people who smoked tobacco and drank alcohol. 15 And a Spanish team found that people who smoke and drink heavily could increase their risk of oesophageal cancer by up to 100 times. 2,16 This problem is made even worse because heavy drinkers and smokers often have unhealthy diets. 17

An American study found that women who drank alcohol during pregnancy increased the risk of leukaemia in their children. 18 Two larger studies are now under way to confirm this result. Until their results are available, pregnant women are advised to stop drinking alcohol.

At the moment, we are not entirely sure how alcohol causes cancer but there are several ideas.

The strongest one is that in the body, alcohol is converted into a chemical called acetaldehyde. Acetaldehyde is the chemical that causes hangovers, but it can also cause cancer by damaging our DNA and preventing it from being repaired. People who smoke and drink heavily have very high levels of acetaldehyde in their saliva 19.

Here are some other theories:

• Alcohol can increase the level of hormones such as oestrogen in the body. Unusually high levels of oestrogen could cause breast cancer. 20
• Alcohol can cause cirrhosis of the liver by repeatedly damaging the liver’s cells. 6 This in turn can cause liver cancer.
• Alcohol makes it easier for dangerous chemicals to be absorbed in the mouth or throat. This includes the chemicals in tobacco that can cause cancer. 2
• Alcohol reduces the amount of folate in our blood. 21 Folate is a B vitamin that our cells need to create new DNA correctly. It prevents changes to our DNA that could lead to cancer.

The more alcohol that someone drinks, the more their cancer risk increases. But even very small amounts of alcohol, as little as one drink a day, can increase cancer risk 22,23. A team of Italian scientists analysed over 200 studies on alcohol and cancer. They were unable to find any lower daily limit of drinking alcohol where cancer risk was not increased. 24

But drinking small amounts of alcohol also reduces the risk of heart disease, although this mainly applies to men over 40 and post-menopausal women. 25

Because of this many sources including the World Health Organisation and the European Code Against Cancer have suggested that women should drink less than two units a day, and men should drink less than three a day. 26 While these levels may increase the risk of cancer, the actual effects are likely to be small.

The risk of alcohol-related cancers increases the more you drink. So by cutting down on what you drink, you can reduce your risk of several cancers.

If you are a heavy drinker, it is not too late to start cutting down. Scientists recently showed that the risk of mouth and oesophageal cancers drops dramatically in heavy drinkers who stop drinking. 27