Drinking Your Way to Cancer

Here’s a piece of research that will make the Food and Drink Nazis happy. A recent British study using a cohort of a million women found that even a small amount of alcohol can increase your chances of getting cancer. Apparently the wierdos at the World Health Organisation have classified alcohol as a class 1 carcinogen along with asbestos, formaldehyde, mustard gas and plutonium-239. Somehow I don’t think a pint of mustard gas and some asbestos crackers would be as popular as a Guinness and beer nuts, but they are supposedly equally as deadly. Yeah, right.

WHO silliness aside, it is, of course, a concern if small amounts of alcohol do indeed cause an increase in cancer. The article quotes a Doug Sellman, a professor of psychiatry and addiction medicine at the Christchurch School of Medicine. This rings alarm bells for me, as I would have thought the best expert opinion would have been from an oncologist, rather than a psychiatrist whose last contact with physical medicine would have been when he specialised. My concerns about the expertise of Prof Sellman, on this topic, are not allayed by his closing remarks:

“Sellman criticised past research that endorsed a glass of wine a day for health, saying it had been funded by alcohol companies. He said the rate of regular heavy drinking could be reduced by raising the drinking age back to 20, banning supermarket sales, raising the price and increasing the amount of drink-driving surveillance.”

I have yet to see any evidence to support the assertion that the health benefits of alcohol have been faked. In fact all the evidence for cardiovascular benefits is quite compelling and of considerably better quality than the current study in question. It is also much better evidence than the evidence for his proposals for reducing heavy drinking. Supermarket sales have made no difference at all to our drinking rate and increased drink-drive surveillance, while an excellent idea for stopping drink-drivers will make no difference to drinking per se. Making alcohol more expensive would indeed work to reduce drinking, just not heavy drinking (the evidence is that these people move to cheaper brands and, finally to home brew). Reducing the drinking age to 18 did indeed increase teenage drunkenness (as every ED doc in the country warned) but has made little difference to overall drinking stats. Besides, I suspect that that particular genie is not going to go back in it’s bottle very willingly.

So much for the “expert” opinion. What about the research itself? My opinion is that it is interesting, but hardly definitive. There are a number of problems with a study like this which prevents it from being anything more than an indication that more study in this area is a good idea.

1. This is an epidemiological observational study – a study where the researchers just observe things. As such, correlation is not causation and a link between alcohol and cancer may be purely circumstantial. For instance, alcohol intake may be a surrogate marker for a more sedentary lifestyle or a diet with more junk food.
2. The amount of alcohol consumed is estimated by the subject themselves, rather than the researchers. People notoriously underestimate their alcohol consumption (ask any ED doc). This means that the conclusion that a small amount of alcohol may cause cancer may be spurious – the actual amount may be considerably higher.
3. Most of the rise in cancer rates are inconsequential (<10%). At these levels the rise may simply be an artifact, again from extraneous causes other than alcohol.
4. The most significant rise (29% for mouth and throat cancers) is not seen in non-smokers who drink, only in drinking smokers. This would indicate that the lining of the mouth and throat would have to be already damaged by smoking before alcohol has any effect. This would be a good reason to stop smoking , rather than stop drinking.

Some further disinformation in the (short) article (not the research).

“Sellman said alcohol killed about 1000 people a year half from accidents but half from chronic disease such as cancer.”

True but misleading. The statement “half from chronic disease such as cancer.” implies that most of these 500 deaths are from cancer. Actually, very few are from cancer, the vast majority of alcoholics die from heart disease with a bit of liver and kidney failure thrown in.

“The statistics showed that for every 1000 women who drank one glass a day, there would be 11 extra cases of breast cancer, one extra case of mouth and rectal cancer and 0.7 each for cancers of the gullet, throat and liver.”

Beware journalists bearing statistics. The actual fact is:

“For every additional drink regularly consumed per day, the increase in incidence up to age 75 years per 1000 for women in developed countries is estimated to be about 11 for breast cancer, 1 for cancers of the oral cavity and pharynx, 1 for cancer of the rectum, and 0.7 each for cancers of the esophagus, larynx and liver, giving a total excess of about 15 cancers per 1000 women up to age 75. [Emphasis mine]”

What this is actually saying is that the marginal increase in your lifetime risk for breast cancer is 1.1% for each extra drink you take regularly. This means the opposite to the gist of the article. It means that at a low intake of alcohol (1-2 standard drinks a day) your increased risk of cancer is trivial. So trivial that it is certainly outweighed by the cardiovascular benefits, if only because your chances of dying from heart disease are much higher than your chances of dying from cancer.

Sigh. Medicine and the media – a mine of misinformation.

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