Alcohol increases the risk of seven types of cancer
From riotous nights in the pub to a quiet glass with dinner, alcohol is an ever-present part of British life. But it has its dark side, leading to hangovers, embarrassment or worse.
After smoking, drinking alcohol is one of the most important and well established causes of cancer – a message that has been clearly backed up by a large new study.
The Million Women Study has just reported that drinking more than two units of alcohol per day can increase the overall risk of developing cancer, as well as boosting the risk of developing seven specific types.
To put things into perspective, two units is the amount in a 175ml glass of wine, or a pint of ordinary strength lager, cider or bitter.
We’ll look into the findings in much more detail in the rest of the post, but its message is clear: the less alcohol you drink, the lower your risk of cancer.
What did the study show?
The Million Women Study includes over 1,280,000 British women. They were recruited between 1996 and 2001 by Cancer Research UK scientists in Oxford, led by professor Valerie Beral.
The study’s latest report looked at how alcohol affects the risk of 21 different types of cancer. According to the results, regularly drinking small amounts of alcohol increases the risk of:
- Breast cancer
- Bowel cancer
- Mouth cancer
- Laryngeal (voicebox) cancer
- Oesophageal (gullet or foodpipe) cancer
- Liver cancer
- Pharyngeal (upper throat)cancer
Some of these effects are pretty substantial. Compared to women who drink two units a week, those who drink two per day double their risk of mouth and laryngeal cancer, and triple their risk of developing a certain type of oesophageal cancer.
Other studies have found the same thing, and the link between alcohol and cancer is now very well established.
What about light drinking?
We’re all aware that binge-drinking can have serious consequences for your health, from alcoholism to cirrhosis of the liver.
But studies like this tell us that as far as cancer goes, drinking much less can still be risky. Drinking just 1-2 units a day can increase your risk of the seven cancers linked to alcohol. And the more you drink, the higher that risk becomes.
And remember that a small glass of wine or a pint of regular-strength beer already contains that many units.
But does alcohol have any benefits?
The study also found that alcohol has a protective effect against certain types of cancer. Women who drink more tend to have lower risk of kidney and thyroid cancer, as well as non-Hodgkin lymphoma. It’s not clear why this happens, although other studies have found the same thing.
Even so, there’s no doubt that these potential benefits can’t compensate for the serious consequences of drinking too much. Indeed, the study showed that drinking two units a day, compared to two a week, increases the risk of cancer overall by 15%.
It’s a clear sign that the risks outweigh the benefits.
That’s especially ironic since some media reports suggest that alcohol could actually prevent some of the cancers we know that it causes. Often, these reports are based on very small studies, or look at cancer cells grown in a plastic dish, rather than real people. Either way, it’s clear that following this advice could be harmful and potentially fatal.
What about wine, or red wine in particular?
Although many people believe that wine, and red wine in particular, is generally good for their health, scientific studies say otherwise.
The vast majority have found that all types of alcohol – beer, wine and spirits – can increase the risk of cancer. The Million Women Study is no exception.
It showed that even women who only drank only wine (about a third of the sample) have a higher risk of cancer in a similar way to women who drink beer or spirits too. Both red and white wines had the same effect.
What about smoking?
The study found that alcohol only really increases the risk of mouth, oesophageal and laryngeal cancers in people who also smoke. Among people who had quit smoking or had never started in the first place, the extra risk was minimal.
However, note that smoking doesn’t cause breast cancer, so drinking one or two units a day will increase the risk of this cancer even in women who don’t smoke.
How many cancers are we actually talking about?
If you look at every woman in the UK under the age of 75, the Million Women Study estimates that every extra alcoholic drink per day is responsible for 15 cancers in every 1000 women. Out of those, the majority (11 out of 15) are breast cancers.
All in all, the researchers estimate that every year in the UK, alcohol causes:
- 5,000 breast cancers (just over one in ten cases)
- 1,200 mouth, oesophageal or laryngeal cancers (about one in twelve cases)
- 500 bowel cancers
- 250 liver cancers
How does alcohol cause cancer?
Alcohol could lead to cancer in several different ways:
- In your body, alcohol is converted into a toxic chemical called acetaldehyde, which is one the main reasons why we get hangovers. But besides giving you a headache in the morning, acetaldehyde can also cause cancer by damaging DNA and stopping our cells from repairing this damage.
- Alcohol can increase the levels of some hormones, such as oestrogen, testosterone and insulin. Unusually high levels of oestrogen increase the risk of breast cancer.
- Alcohol makes it easier for the tissues of the mouth and throat to absorb the cancer-causing chemicals in tobacco. This is one reason why people who smoke and drink multiply the damage they receive and have especially high risks of cancer.
- Drinking lots of alcohol can damage the cells of the liver, causing cirrhosis, a disease that makes people more vulnerable to liver cancer.
The bottom line
For many of us, alcohol is a regular and enjoyable part of our lives. But it’s important that we at least realise how our drinking habits can affect our health.
Many people associate alcohol with social problems and when health comes into it, it’s usually associated with heavy binge-drinking.
Unfortunately, it’s clear from studies like this that what most of us would consider as “light” or even “moderate” drinking can affect the risk of several cancers. You don’t need to be drunk to increase your risk.
Cancer Research UK’s recommendation, which is echoed by other charities, is to limit how much you drink to small amounts – one small drink a day for women or two for men. At these levels, any risk would be fairly limited.
And, of course, every bit you can cut down will help to cut your cancer risk.
Ed
Updated with Reference: N. E. Allen, V. Beral, D. Casabonne, S. W. Kan, G. K. Reeves, A. Brown, J. Green (2009). Moderate Alcohol Intake and Cancer Incidence in Women JNCI Journal of the National Cancer Institute DOI: 10.1093/jnci/djn514
Comments
Ed Yong March 23, 2009
Andrea, you can read more about stress and cancer on our Healthy Living site, but essentially there’s no good evidence to link the two. It is, however, possible that stress could be indirectly linked to cancer because stressful situations can make some people more likely to smoke, drink heavily, overeat and so on.
Jopsychology March 14, 2009
This was an informative piece of reasearch. I welcome updates on all reserach conducted by Cancer Research UK. I would like to believe that I am intelligent enough to process such information and then make an informed decision about it. Good work CRUK – keep it up!
Ed Yong March 17, 2009
Thanks! We appreciate and agree with your sentiments!
Chris Brown March 13, 2009
It is disappointing to see risk numbers being quoted only in relativistic terms and not in absolute terms as well. This is important because the risk of a particular disease may increase ten fold under certain circumstances but if this is from 1 in 1,000,000 to 1 in 100,000 I am not worried. But a ten fold increase from 1 in 100 to 1 in 10 is much more of a concern.
Ed Yong March 17, 2009
Chris – the post above does actually have some absolute numbers in the “How many cancers are we actually talking about” bit. We’re also in the process of updating our figures for lifetime risk estimates of different cancers, which are currently based on 1997 data.
Margaret M March 13, 2009
I despair of the ever changing guidelines for healthy living presented to us laymen by enthusiastic researchers.
My grandfather lived by the maxim ‘moderation in all things’. Why is this common sense attitude forgotten whilst we become ever more anxious about what we perceive to be conflicting advice?
A little alcohol may give the heart protection we read about and certainly takes the edge off a bad week – but it stands to reason that too much alcohol would be harmful to us and society in many ways.
So, provided there are no existing health or medication issues, my answer to Laura would be ‘say goodbye to the confusion Laura; so long as you’re not the kind of person where one drink leads inevitably to a basinful, in which case abstinence is the only answer, then my view is to just enjoy a couple of glasses of wine or beer at the weekend and relax’.
Is that reasonable Ed?
Ed Yong March 17, 2009
Margaret – that certainly sounds reasonable. The guidelines that have been presented by health organisations have actually been remarkably consistent for a while now. Our own recommendation, which is echoed by other charities, is to limit how much you drink to small amounts – one small drink a day for women or two for men. At these levels, any risk would be fairly limited.
Sue Pitts March 13, 2009
So was my breast cancer caused by 1 drink a day or by HRT, dual hormone, for over 10 yrs?
I’m sure my GP would rather blame my drinking!
Ed Yong March 17, 2009
Sue – it’s usually impossible to pin down a single cause for most cancers. Cancer is a complicated disease. Many steps need to happen before a normal cell becomes a cancerous one, and there are many different things that can affect the risk of any given type of cancer. Breast cancer, for example, has been linked to alcohol and HRT, as you say, as well as body weight, inactivity, how many children you have and many other things.
Samantha March 13, 2009
I like a drink as much as the next woman. I can see from the comments above that we just “don’t want this to be true” about drinking as we all like doing it! As someone else asked; have all other factors including increases in chemicals in deoderant and our households been taken into account in the data?
Ed Yong March 17, 2009
Samantha – the authors accounted for smoking, body weight, physical activity, use of hormone replacement therapy and use of oral contraceptives (the Pill). They didn’t look at household “chemicals” or deodorants because these things have not been convincingly linked to breast cancer. See this previous post for more.
Ed Yong March 1, 2009
Laura, the confusion is understandable. Unfortuntely, it’s not just a case of alcohol either being bad or good.
Studies have consistently found that drinking too much alcohol can increase the risk of cancer, and that even drinking small amounts could have an effect.
Small amounts of alcohol could protect against heart disease. However drinking too much alcohol actually increases the risk of heart disease.
This is why organisations like ourselves, the World Cancer Research Fund and the American Cancer Society suggest that people limit their drinking – to one small drink a day for women or two for men.
laura February 28, 2009
im confused.either alcohol is not gud or it is.it says it can protect against cancer aswell as cause.also it may protect against heart conditions.help im so confused.
Pieter February 26, 2009
While everyone can question the analysis based on statistical sampling and regression and whatever technical terms you want to throw out there, I would rather have the results and consider the potential of alcohol being the possible cause of certain illnesses rather than not have it. The results would surely not stop people from drinking just as results of smoking studies do not stop people from smoking but it is nice to have the option and consider a possibility.
Ed Yong February 26, 2009
The authors have indeed accounted for potential “counfounding factors”. For the technically-minded, the following comes from the paper:
Cox-regression models were applied to estimate relative risks (RR) of each cancer site of interest associated with various measures of alcohol intake, using attained age as the underlying time variable. There was no evidence that the proportional hazard assumption was violated. Data were stratified by region of residence (ten areas covered by ten cancer registries), and adjustments were made for quintiles of socioeconomic status (using Townsend’s deprivation index, which includes measures of unemployment, overcrowding, owner-occupier status and car ownership for the postcode area of each participant, based on the 1991 National Census); smoking (never, past, current smokers <10, 10-19, ≥20 cigarettes/day); body-mass index (<25, 25-29, >30 kg/m2); physical activity (strenuous exercise <1 or ≥1 times per week ); ever use of oral contraceptives (yes, no); and use of hormone-replacement therapy (current, past, never).
And this is what the paper says on the topic of underreporting:
Reported alcohol intake was found to be highly reproducible in this study (17) and we addressed potential regression dilution bias by using repeat measures of alcohol intake taken approximately 3 years after recruitment (9, 10). This cannot address the potential problem of systematic under-reporting of alcohol intake that is known to occur in heavy drinkers (18), but this is thought to be less of a problem for low to moderate intake (19). Hence, although some uncertainty remains about the true quantitative effect of alcohol on cancer incidence, the effect of systematic underreporting is unlikely to be a major problem here.
And once again, you can see the paper itself here.
john nagle February 26, 2009
As a practising GP I am aware that most people under-report their levels of alcohol consumption especially when talking to health professionals. It is not clear that the authors considered this possibility when reporting their conclusions.Clearly such under-reporting would have the effect of increasing the apparent effect of ‘low levels of alocohol’.I would like to know if any attempt was made to validate the self reports of alcohol use by ,for example, in depth interviews with a random cohort. Without such data validation the conclusions must remain suspect.
datacharmer February 25, 2009
Unfortunately I can’t access the article – the link to the athens login page seems to be broken – so I’m not sure to what extent the researchers address my concerns.
The elephant in the room here is ethnicity. Incidence of breast (and some other types of) cancer amongst white women is much higher than for women of a different ethnic origin (see for example here: http://www.zoladex.net/80778?itemId=4841753), which presumably is partly due to genetic factors. At the same time white women tend to drink a lot more than average due to cultural reasons, while minorities (e.g. Pakistanis and Bangladeshis) don’t drink at all in many cases. Furthermore, even amongst white women, whether and how much to drink is a choice; health-conscious women will not only drink less but they will also generally lead healthier lifestyles and avoid other harmful, ‘cancer-generating’ activities.
There are plenty of other potential issues (e.g. the word ‘age-standardised’ is conspicuously absent from the abstract), but I can only speculate. I’d be grateful if you could email me a copy of the original article and then I can offer more specific commentary.
JaneR February 25, 2009
Fair enough to mention other studies here in your blog, but this report is meant to be about this study. It should say “the study has found a link between drinking 1-2 units of alcohol per day and breast cancer in all women, and links between 1-2 units with other cancers in women who also smoke.” Later you could say that other studies have founnd links independent of smoking. I’m just not sure it’s been reported accurately, possibly making it needlessly scary. A study about people who drink 6 units a day is a bit of a red herring, that’s a different group of people.
Ed Yong February 25, 2009
Jane, we take your point, but it’s not to say that non-smoking drinkers do not face any risks to their health. They will still have higher risks of breast cancer, and potentially other types too.
It’s also worth clarifying that some other studies have found that alcohol can increase the risk of mouth, oesophageal and laryngeal cancers independently of the effects of tobacco.
One recent analysis of 15 studies found that alcohol consumption doubles the risk of head and neck cancers (which include mouth, oesophageal and laryngeal) even in non-smokers. However, this only applied to people who drank six or more units a day. It may be that the Million Women Study didn’t find the same effect, because very few women in the study group drank at these levels.
JaneR February 25, 2009
The fact that “alcohol only really increases the risk of mouth, oesophageal and laryngeal cancers in people who also smoke” (which comes as an aside more than half way down) should be more prominent: the write-up makes it sound like alcohol affects everyone equally. There are a lot of non-smoking drinkers out there who may be unduly worried.
Dr Roger February 25, 2009
Thank you for that swift response. I can see where you are coming from, but I’ve now looked at the conclusions of this paper and they absolutely claim that their results sustain a _causal_ relationship between alcohol consumption and cancer.
Too right, “correlation does not imply causation “, and correlation is all this paper has. Nothing in the paper, not the data or the analysis, could sustain the conclusion of causality. I am sure that all the other studies to which you refer are unlikely to have overstated the weight which can be placed on their individual conclusions of causality, but this one does.
Would it hurt too much to represent the actual significance of this study by writing in the conclusions something like ‘..is associated with..’ instead of ‘..caused by..’?
It’s just basic scientific honesty and clear thinking. I’m not disputing the results, I’m just depressed by the slack wording, which so often betrays slack thinking and thus can throw doubt on the whole enterprise.
Ed Yong February 25, 2009
We appreciate that correlation does not imply causation.
However, in the case of alcohol and cancer, a causal association has already been inferred by a significant body of previous evidence. As far back as 1998, the International Agency for Research into Cancer concluded that alcohol was “causally related” to several cancers based on the available evidence and studies have only provided support for that conclusions ever since. Recently, the World Cancer Research Fund concluded that:
The evidence that alcoholic drinks are a cause of cancers of the mouth, pharynx, larynx, oesophagus, colorectum (men) and breast is convincing. They are probably a cause of liver cancer, and of colorectal cancer in women.
The evidence is very consistent. There are dose-response effects (the more you drink, the higher the risk). There are several plausible mechanisms through which alcohol could lead to cancer, which have been backed up by basic biological research. Given this large body of research, it is no longer “speculative” to talk of causal connections as it would for other less well-established risk factors.
Dr Roger February 25, 2009
The reporting of this research is all saying the cancer is ’caused by’ drinking, rather than ‘statistically associated with’, which I suspect is the actual conclusion of the study.
In that case, it would be statistically just as valid to conclude that cancer causes drinking, or that both are associated with some third common factor. Medically, there may be reasons to conclude that these alternatives are less likely, but unless the chain of events has been pinned down exactly it is speculative to infer or imply a causal connection, much less assume one.
Journalists are frequently guilty of sloppy thinking and consequent loose talk of this sort. Charities associated with research are rightly expected to be a little more cautious and reliable.
Can you _prove_ the causal link that your text assumes? I doubt it. If you can’t, you should be ashamed.
Ed Yong February 25, 2009
amt – This research has just been published in the Journal of the National Cancer Institute. This blog post was published as soon as the embargo on the article lifted last night, and the journal typically makes the article available shortly after. We have now added a citation for the research so you can check out the methods for yourself.
For anyone wondering about the whereabouts of the first three comments, we have deleted them. We have strong reason to believe that all three were posted by the same individual using different names. This practice is known as “sockpuppetry“, which means to create fake online identities to create the false illusion of mutual support. We are not averse to criticism (as shown by the comments above), but sockpuppetry is unacceptable online behaviour.
Dr Michael Coleman February 25, 2009
Amt is so right. Evidence? What evidence? What we have here is a wholly unsubstantiated statement. Show me why these million women developed their cancers because of their low alcohol intake rather than the million other things that ‘pollute’ their bodies or their environment. What nonsense….
Cheers!
As a biomedical graduate student I find the research and method of disseminating your findings shaky and potentially unethical. where is the actual data? where is this being research being published? I don’t see any real data published here just reviewing your own research before actual publication which is typically the sign of poor research (i.e. report about your study before being published and peer-reviewed so that you can drum up interest.) Without seeing the specific type of study performed and what statistical analysis were performed no one can discuss the validity of your research. What about possible confounders? Your commentary is full of false statements based on existing reputable biomedical research that you pass off as “scientific fact”. This alone raises serious questions about how trust worthy your research and methods are. Without a careful review of your study methods, statistical analysis, sponsorship, etc there can be no valid review of your research and thus your comment and claims are not valid.
Andrea March 23, 2009
This research has really put the frighteners on me. As someone at 43 with no apparent risk factors, I have continually wondered why I contracted oestrogen sensitive breast cancer. I could only think of alcohol or stress as causes. I have never been a heavy drinker but do use my 14 units a week ‘allowance’, thinking I was safe. No-one on this posting has mentioned stress. Is this a serious contender for causing cancer and if so, are its damaging effects countered slightly by the occasional ‘de-stressing’ glass of wine?