Unless you’ve been hiding in a Colombian cave for the last few weeks you’ll have heard the reports that alcohol causes cancer. This isn’t really that shocking. Scientists have been investigating this link for decades. I’m sorry to say it but: yes. Alcohol increases your risk of developing cancer. But don’t be alarmed just yet; the risk varies depending on how much you drink. So what’s your risk? I’ll answer that, but first things first….
‘Everything’ causes cancer, how do we know alcohol does?
Years of research have pointed to a link between alcohol and cancer1, though obviously this alone is not proof. Cheese consumption and people dying whilst tangled in their bedsheets correlate2, but that doesn’t mean ‘cheese nightmares’ are deadly. Or real3. Many other things may explain the alcohol and cancer correlation, so how do we untangle this mess?
This is done by carrying out ‘observational’ studies, whereby a large number of people are asked about their lifestyle habits, and these are compared with an outcome, such as developing cancer. This, however, relies on both the memory and honesty of the people taking part. It won’t be so surprising that people tend to frame themselves in a more favourable light, and this must be taken into account when interpreting the data. We also have to be sure that the results can’t be explained by something else, such as your BMI, diet, whether you’re a smoker, and your level of exercise etc. This is called ‘correcting’ the data. We cannot control what people do in their lives (thankfully), therefore, it can be difficult to be absolutely certain of what the results mean. Fortunately, there are things we can do that help us to trust our results.
So, what evidence do we need to be more sure that alcohol causes cancer? Well firstly, we need cancer cases to correlate with alcohol consumption, after correcting for other explanations4. Next, we need meta-analyses of multiple studies to find the same correlations5-7. We also need evidence that the risk of cancer reduces when alcohol consumption ceases.8-10 So far: check, check, and check. Finally, we need a biological explanation for how alcohol actually causes cancer, and so far there are many suggestions for this.6,11 It seems that the only thing that is likely to change now is the size of the risk, not the fact that there is a risk4. So what is the risk?
The risk depends on how much you drink…
This is not an all or nothing scenario; if the amount you drink is low, your risk is also low. In terms of the research, ‘one drink’ contains 1.5 UK units, which is roughly equivalent to a bottle of average strength beer, a small glass of wine, or a large spirit measure. If you are a light drinker (up to 7 drinks/week) you have a 5% greater overall risk than a non-drinker.12,13 The risk increases if you drink more than this, and it seems to be greater for women than men, though this seems to be mostly caused by breast cancer.13 The risk is greater still for smokers, due to the dangerous effect of combining these two vices.11,14
It also depends on which cancers we are talking about
The risks are higher still when you consider individual cancers, and this is where the amount you drink really starts to become more important. At the moment, seven cancers are thought to be caused by alcohol, however this list may grow.4 These include those of the larynx (voice box), oropharynx (mid throat), oesophagus, liver, colon, rectum, and female breast. The increased risk for light drinkers is fairly low again, they are 1.05-1.25 times more at risk than a non-drinker, depending on the cancer5. For moderate drinkers (up to 28 drinks per week), the risk can be over two times greater than non-drinkers, meaning you are twice as likely to develop one of these cancers. Head and neck cancers show the highest risk here5. Heavy drinkers (over 28 drinks per week) start to reap the risks; they are up to five times more likely to develop head and neck cancers, and twice as likely to develop liver cancer, than someone who does not drink5.
So what’s the take home message?
There isn’t really a lower limit where there is zero risk13. Also, don’t assume a small amount of daily alcohol will protect you against heart disease; doubt has been cast over that as well4. Alcohol has been linked to multiple diseases15, but we don’t drink alcohol to keep us healthy, we know it is bad for us (the hangovers alone show us that). There is also a lot we don’t know yet, for instance, are all drinks equally risky? What about binge drinking? Although there is some data on this, it is too early to know for sure4. Although the risks start with your first drink13 nothing is guaranteed in cancer; individual genetic differences between people, as well as other lifestyle features, are also important in determining your individual danger. The take home message is simple. Heavy drinker? Cut back. Light drinker? Know the risks involved.