Moderate drinking: risk Vs reward?

A study recently published in the BMJ found that alcohol consumption, even at moderate levels, is associated with adverse brain outcomes. The research also found no support for a protective effect of light consumption on brain structure. The authors, from Oxford University and University College London, concluded:

These results support the recent reduction in alcohol guidance in the UK and question the current limits recommended in the US.

The research may be seen in the context of the much debated J-shaped curve suggesting potential health benefits of alcohol consumption at lower risk levels. Indeed another recent BMJ study found evidence to support the potential protective effects of moderate consumption on cardiovascular disease (CVD), addressing some of the previous question marks over the CVD protective effects research. However expert reactions highlighted several reasons why drinking should not be taken up by abstainers for any potential CVD benefits.

In producing the new UK 'Low risk drinking guidelines' last year, the Chief Medical Officer's (CMO) group considered the evidence that moderate drinking may reduce risks of death alongside 'a large body of evidence' demonstrating that these potential benefits are likely to be overestimated due to the limitations found in most studies of the long-term health consequences of alcohol consumption.

The group also factored in modelling by the University of Sheffield which included protective effects for some health conditions weighed against the alcohol-related risks of mortality from others. The conclusions were:

1. Any benefit to cardiovascular health for moderate drinkers in the UK is largely cancelled out by their increased risk to health from other diseases, and
2. Any remaining benefits to health from moderate drinking are small and uncertain. (See here for more details)

The Oxford/UCL study, which scanned for structural brain changes such as hippocampal atrophy, grey matter density, and white matter microstructure in the Whitehall II study cohort, has its limitations too of course, summarised in an NHS Choices explainer as:

• The participants are all people who were civil servants in the 1980s and were mostly male and more middle class and higher IQ than the general population, meaning results might not be applicable to the UK as a whole.
• The effect of hippocampal atrophy was found in men and not women which may be down to the lower sample size of women and that few of them drank heavily.
• The information on alcohol intake was self-reported and therefore might be inaccurately reported by participants.
• It is difficult to link brain structure with alcohol intake when it might have been down to other confounding factors such as intelligence, cognitive stimulation and other lifestyle factors.
• The MRI scan only took place once, at the end of the study, so it is difficult to tell if and when any changes in brain structure took place and rule out other influencing factors.

No safe level?

Of course such studies do not intend to suggest that alcohol does not have potential social benefits, rather than the seek to answer the question of the possible health implications of moderate consumption - an issue that seems to generate substantial public and media interest. Back in January 2016 when the revised guidelines were announced, an article in the Telegraph covered a range of responses to the 'Low risk drinking guidelines', from health professionals discussing risks to critics of the guidelines calling nanny statism. We also published our own expert reactions on the revised guidelines and media reaction, also followed by an analysis of Twitter reactions.

This latest studies nudge the argument further along the current direction of travel regarding potential health risks and benefits: light drinking probably won't make you healthier; potential CVD benefits need to be considered against other risks. A somewhat tricky message, but as Matt Field, Professor of Addiction at the University of Liverpool, put it in the Telegraph: 

Any amount of alcohol consumption carries some risk. However, it is important to bear in mind that most activities that people undertake on a daily basis - e.g. driving to work - carry some risk, and people need to make informed choices about the level of risk that they are prepared to accept.

In his APE: Alcohol and Epidemiology blog, John Holmes discusses the difficulties of turning research findings - which posit different levels of risk for different diseases - into simple health promotion messages that are 'scientifically robust, sufficiently compelling and easily understood'.

He highlights a recent meta-analysis of cancer and alcohol research supports the judgement that 'alcohol causes cancer of the oropharynx, larynx, oesophagus, liver, colon, rectum and breast', although the risks are pretty small at low levels of drinking. However, as mentioned above, the CMO's evidence review considers many other conditions, including ischaemic stroke, ischaemic heart disease and type II diabetes, which show U- and J-shaped relationships, indicating a beneficial effect of alcohol at some levels of consumption and a detrimental effect at others.

While addiction professors and epidemiologists may feel confident in making informed choices from the complex information available, the degree to which the wider public choose whether or not to take notice of the CMO's headline messages on lower risk drinking will remain a hot topic.