I'm completely ignoring the mental pollution - er, I mean the "article" - and focusing on the study, seen here (linked in the article):
http://onlinelibrary.wiley.com/doi/10.1111/add.13477/full
I know a lot of people will poke fun at the guardian for posting such dreck, and it's completely deserved... But I figure as long as it's posted here on the forums, I might as well deconstruct and lay bare some of the conclusions arrived at by the study within and possibly put to rest some of the worries that might be festering at the back of people's minds.
I've shortened some paragraphs and concepts by use of ellipses [...] for readibility, and I don't intend on hijacking, misconstruing, or misleading by their use. The article is open and available for all to read. All emphasis mine. Geez, what is this, a newspaper?! Enough with the disclaimers already!
The use of causal language...is patchy, with titles of papers and newspaper headlines often choosing to describe a causal association as a ‘link’ between alcohol and cancer. Expressions such as ‘alcohol-related cancer’, ‘alcohol-attributable cancer’ and the effect of alcohol on ‘the risk of cancer’ incorporate an implicit causal association, but are easily interpreted as something less than cancer being caused by drinking.
...there seems to be particular confusion about two aspects of ‘alcohol causes cancer’, the first being the meaning of ‘cause’ and the second being the quality of the evidence.
The meta-analyses have not been able to describe the influence of pattern of drinking on cancer risk...due to insufficient data in the component studies. However, recent analyses from two large cohort studies in the United States do not suggest a significant impact of drinking pattern on risk of total cancer in light to moderate drinkers
The strength of the association with alcohol varies by site of the cancer, being particularly strong for mouth...and less so for colorectal cancer, liver and breast cancer. For cancers of the mouth, pharynx, larynx and oesophagus there is a well-recognized interaction of alcohol with smoking [tobacco], resulting a multiplicative effect on risk. Biological evidence is supportive of the carcinogenic potential of drinking alcohol and the interaction with smoking [sic]...
...evidence that, for some cancers, the risk associated with alcohol attenuates when drinking ceases...the risk of oesophageal cancer and cancers of the head and neck increased for a period of years before declining, and was similar to never drinkers after 20 years. A recent systematic review of the risk of laryngeal and pharyngeal cancers after quitting also found that the risk was reversible, with a reduction of approximately 15% of the excess risk in 5 years, and equivalence with never drinkers after more than 30 years.
The effects of light to moderate drinking on cancer risk have had special attention recently...women who drank between 70 and 140 g of alcohol per week had a 5% increase in total cancer compared with those drinking less than 20 g per week...
In this study, alcohol-related risk of aerodigestive cancers was limited to women who smoked
Pure ethanol does not act as a carcinogen in animal studies...for cancers of the mouth, pharynx, larynx, oesophagus and liver there is strong evidence that DNA damage is due to
acetaldehyde. Most ethanol will be metabolized to acetaldehyde in the liver...as further metabolism to acetate is limited at the site. There is some evidence of another
causal pathway through alcohol facilitating access for other carcinogens, such as
tobacco constituents, by enabling the penetration of the mucosa in the
upper aerodigestive tract.
This would go some way towards explaining the interaction between alcohol and smoking for head and neck cancers.
Proof is impossible in epidemiology
In making judgements about causation...there is no checklist or statistical method for inferring causation. Judgement largely employs inductive reasoning, conjecture and refutation.
Firstly, this article gains a lot of its data from a breast cancer study called
The Million Women Study which was focused primarily on breast cancer of women 50 and over, but apparently did screen for many different types of cancer. The website itself actually has some interesting statistics and is worth a read.
As for the "7 sites", it's total hogwash. Colorectal, liver, and breast cancers are "less associated" with drinking. An association that I believe is weak to non-existant, but without hard numbers, it's impossible to tell. I'll admit that liver cancer is probably more highly likely with
heavy drinking. Mouth, pharynx, larynx and oesophagus cancers are more associated with drinking when paired with smoking tobacco, most likely cigarettes.
Something to note is the words "causal" and "causation" are heavily used to describe the relationship between drinking and cancer.
The conclusion goes on to rant for 2 paragraphs about the alcohol industry's "vitrually unlimited resources", dangers of not setting a "safe level" of drinking, and promoting alcohol for so-called health benefits. Soapboxing in a "scientific" study.
This is plainly and simply
NOT SCIENCE. Science relies on controlled and controllable variables and repeatability. There is no definitive data to be gleaned from this paper, nor is it a valid study. It's purely - as it says - inductive reasoning, conjecture, and refutation. It takes data from an unrelated 20 year study and massages it to fit a propagandistic message.
Carry on brewing, my brothers and sisters!