One or two units of alcohol a day can increase the risk of cancer

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?

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!

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.

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?

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!

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?

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.