A beer a day to raise your risk of prostate cancer? Don’t believe it

    17 November 2016

    Having just a drink a day could raise men’s risk of prostate cancer by a fifth, a study published in BMC Cancer has claimed.

    However, the study’s conclusions have been cast into doubt (see our analysis below).

    Prostate cancer is the most common type of cancer among men in Britain. There are 47,000 new cases diagnosed every year, and 11,000 deaths.

    Research so far has not found a clear link between prostate cancer and any behaviour, whether smoking, alcohol or poor diet.

    Studies investigating prostate cancer and alcohol have been contradictory.

    The latest research claimed to find a ‘significant’ relationship between alcohol intake and risk of prostate cancer. The more you drank, it argued, the greater the risk.

    The study’s authors said: ‘Given the high prevalence of prostate cancer in the developed world, the public health implications of these findings are significant. Prostate cancer may need to be incorporated into future estimates of the burden of disease alongside other cancers (eg, breast, oesophagus, colon, liver) and be integrated into public health strategies for reducing alcohol-related disease.’

    Iain Frame, director of research at Prostate Cancer UK, told the Times: ‘It is already well known that alcohol plays a role in development of some cancers. However, the impact is unclear when it comes to prostate cancer specifically.

    ‘This systematic review comparing previous research looking at possible links between alcohol consumption and prostate cancer serves to highlight just how difficult it is to undertake studies which provide conclusive evidence as to the true impact of one item in the diet over any other.’

    Instant analysis
    The study begins with a fact: that the evidence for causality between drinking and prostate cancer is equivocal.

    The authors identified 340 studies on the subject, but then junked 313, performing a meta-analysis on the remaining 27. They discarded studies that did not express the data in terms of weight of alcohol consumed daily, and even studies that referred to specific types of alcohol. How this can be fair I struggle to understand.

    These 27 studies suggested either no effect, little effect or slightly more effect on cancer rates, with a significant number suggesting a null hypothesis.

    Then the study authors began work on ‘weighting’ different studies, adjusting for such things as recall bias – and found a dramatically different conclusion.

    To me this looks like the authors fit the data to reflect the opinion they had at the outset.

    The research was then spun in the media to sound more important and alarming than it really is. The study concluded that moderate alcohol consumption can increase risk of prostate cancer ‘by a fifth’. Actually, the odds ratio is around 1.09-1.10 (broadly translated as an increased risk of nine or 10 per cent).

    As one’s risk of prostate cancer is low, then this increase is much smaller than the headlines suggest.

    The elephant in the room here is the junking of 90 per cent of the studies found.

    I would greatly like to see how the study data would have looked had they tried to make an effort at converting the existing consumption data within the other 313 studies to give a much more powerful conclusion.
    Research score: 2/5