The link between alcohol and cancer

by Jennifer Bowden / 27 October, 2012
Fact: alcohol is a well-known carcinogen. It’s too bad more people don’t believe it.
The link between alcohol and cancer


Alcohol is one of the most well-established causes of cancer and is classified as a carcinogen by the International Agency for Research on Cancer. Yet one in 10 Europeans don’t know that alcohol is a carcinogen, according to a 2010 European Commission report. More worryingly, one in five EU citizens simply don’t believe alcohol increases cancer risk, and just 13% of New Zealand respondents, in a Cancer Society survey, mentioned reducing alcohol intake as a way to lower cancer risk. Is it ignorance? Or is the scientific evidence not compelling enough for some people? Certainly, recent research presented startling new evidence on how alcohol causes DNA damage in humans and therefore our cancer risk. But let’s start at the beginning …

About 30 years ago, scientists discovered an association between alcohol and cancer. Still, that observation alone didn’t prove alcohol caused cancer; more investigation was needed. For starters, did alcohol exposure precede cancer development? Numerous long-term studies, in various populations, have since confirmed healthy people who drink alcohol are more likely to develop cancer. If the disease risk associated with an exposure is sizeable, this suggests the relationship is causal and not a chance association. The cancer risk associated with alcohol consumption is significant. For example, drinking six units of alcohol a day (equivalent to two pints of beer or three glasses of wine) triples the risk of mouth cancer and doubles the risk of oesophageal cancer; greater alcohol levels increase the risk further to up to five or 10 times that of non-drinkers. This dose-response relationship further suggests that alcohol causes the increased cancer risk. Still, a plausible biological explanation for the relationship is needed.

The strongest theory is our body breaks alcohol down into acetaldehyde, and the acetaldehyde attaches itself to our DNA, forming so-called DNA adducts that interfere with DNA activity in a manner that’s linked to cancer-cell formation. People who smoke and drink heavily have high levels of acetaldehyde in their saliva. At an August meeting of the American Chemical Society, researchers presented the first evidence in humans to support this theory. Ten human volunteers were given increasing doses of vodka once a week for three weeks. Levels of DNA adducts in the volunteers’ oral cells increased 100-fold within hours of drinking the alcohol, before declining after about 24 hours. “These findings tell us that alcohol, a lifestyle carcinogen, is metabolised into acetaldehyde in the mouth, and acetaldehyde is forming DNA adducts, which are known major players in carcinogenesis,” said Silvia Balbo, the
lead researcher.

Alcohol may also increase cancer risk by boosting hormone levels, such as oestrogen, that’s linked to breast cancer, for example; by repeated damage to liver cells, resulting in cirrhosis and liver cancer; by acting as a solvent and allowing damaging chemicals to be absorbed in our mouth and throat; and by increasing body fat levels that in turn increase cancer risk. Still, some people hold to the theory that moderate drinking reduces cardiovascular disease risk and therefore on balance may be health-promoting; this theory is far from proven, and balanced against a well-established increased cancer risk seems foolhardy. What’s more, a recent study published in Circulation Research revealed some startling truths about red wine and heart health.

A group of 67 men consumed gin, red wine or non-alcoholic red wine for four weeks. Those drinking non-alcoholic red wine had increased circulating levels of nitric oxide, a molecule that relaxes blood vessels, and their blood pressure decreased by about 6mmHg in systolic and 2mmHg in diastolic blood pressure, potentially reducing their heart disease risk by 14% and stroke by 20%. In contrast, alcoholic red-wine drinkers’ blood pressure changed very little, and gin drinkers’ not at all. This suggests the polyphenols in wine may be the beneficial health component, whereas the alcohol in red wine may actually weaken its ability to reduce blood pressure. Deny it or ignore it, but the fact is alcohol is a proven carcinogen. Still, one hopes initiatives like alcoholandcancer.eu will educate people about the risks associated with alcohol and maybe encourage healthier drinking patterns.

Email: nutrition@listener.co.nz, or write to “Nutrition”, c/o Listener, PO Box 90783, Victoria St West, Auckland 1142.
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