An Aperol a Day: how even moderate drinking affects our brains
You may have wondered how your grey cells are affected by how much you drink. You may have wondered if some people are born to be alcoholics, or whether it is just an unfortunate series of life experiences and personal decisions. Scientists are undertaking hundreds of studies into the relationship between alcohol and our brain structure – a few examples of which will be reviewed here.
Generally speaking, the study of the neuroscience of alcohol tends to look at the pathology of drinking – in other words, excessive drinking of alcohol. This is broadly understood as regularly drinking more than 14 units every week.[1] To test how alcohol affects the brain, many studies use a sliding scale of how much alcohol people drink a week to observe what different effects are seen. People of course tend to underreport how much they’ve drunk – the famous influence of social desirability – so this is always something to bear in mind with this area of research.
This review will be split into three parts, each looking more closely at the genetics and brain differences involved in our behaviour around alcohol. Most studies look at the brains of people with alcoholism, but research is now starting to look at how the brains of moderate drinkers may also be affected by alcohol. This is Part I: ‘An Aperol a Day: how even moderate drinking affects our brains.’
It will come as no surprise that drinking too much doesn’t do wonders for your brain. Copious research has shown the resulting impacts – for example, studies show that drinking heavily can shrink our grey matter[2], degrade our white matter[3], and overall reduce the number of our brain cells[4]. These effects are seen all over the brain for those with what is classed as an alcohol use disorder (alcoholism). But what about those of us who drink moderately? Are those same alarming effects observed for those of us who enjoy a beer each evening? Research has previously been torn between whether it’s harmful or not to drink at moderate levels, with varying results across the board. However, one study set to prove a more definitive answer to this pressing question.
Several months ago, researchers across the US and Europe collaborated to investigate the effects of alcohol on the brain, testing an enormous sample of 36,678 people[5]. The brain scans and health information of these people were sourced from the UK Biobank, one of the largest biomedical databases which looks at the question of nature or nurture in disease. Most of these people were generally healthy middle to older age adults, who reported that they drunk a moderate amount every week – averaging at 1-2 units a day, or just one drink. The researchers analysed their brain scans in relation to how much they drunk. This showed that even moderate drinkers showed the same type, though lesser, negative impacts on the brain. These included a smaller brain volume, smaller grey matter volumes in very specific regions, and notable damage to the microstructure of white matter. In particular, the frontal areas of the brain were found to be affected – these areas are the ones involved in so-called “higher thinking” or executive function. This includes your ability to make decisions, solve problems, and other aspects of thinking like memory and motivation – all of which will be incrementally impacted by drinking such a low but consistent amount. These detrimental associations only worsened the more the individual drank, meaning that it very much appears to be the thin end of the wedge. These results chime in with recent research findings of smaller brain volumes in people who drink moderately.[6] It’s certainly not great news for those of us who enjoy a drink in the evening. However, it is unlikely that such a small but consistent alcohol intake would accumulate damage to a significant extent. This is also something to bear in mind: that whilst observable, these differences would rarely result in any impairments of daily functioning.
Despite these fascinating and rather uneasy results, it must be noted that this study is fully dependent on the data from the UK Biobank, which consists of mainly white European participants. As well as this, only one age group – middle to older aged adults – is considered. Thus there is a crucial need for further research to test this on a wider and more representative sample set. And, as mentioned previously, the people involved used self-report to indicate how much they drunk – this is the most efficient way of testing a study of this size, but it means quantities are liable to bias and distortion from those who want to seem less of a boozer than they actually are. And most importantly, though it is certainly an exciting new avenue for research into how alcohol affects the brain, this study was correlational. This means we can only be sure that as alcohol consumption goes up, so do the scale of the negative impacts on the brain. However we cannot be sure if this is the only thing responsible, or whether other factors are involved. Thus, we must be cautious when describing the causality of drinking alcohol and brain damage.
Overall, this fresh piece of research takes an interesting and controversial area and makes some headway into understanding how the brains of moderate drinkers are affected by what they drink. Moderate drinkers aren’t safe from the same effects that alcoholics experience, but the detriments are unlikely to spill into daily functioning. And, as always, wider and more representative research is needed to take these findings across the world.
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Follow through to Part II: ‘Alcoholism: is it in your genes?’ and Part III: ‘The Age of the Frontal Lobe’!
References
[1] NHS (n.d.) Alcohol Misuse. NHS. Available at: https://www.nhs.uk/conditions/alcohol-misuse/
[2] Yang, X. et al. (2016) Cortical and subcortical gray matter shrinkage in alcohol-use disorders: A voxel-based meta-analysis. Neurosci. Biobehav Rev. 66, 92–103.
[3] Monnig, M. A., Tonigan, J. S., Yeo, R. A., Thoma, R. J. & McCrady, B. S. (2013) White matter volume in alcohol use disorders: A meta-analysis. Addict. Biol. 18, 581–592.
[4] Zahr, N. M. (2014) Structural and microstructural imaging of the brain in alcohol use disorders. Handb. Clin. Neurol. 125, 275–290.
[5] Daviet, R., Aydogan, G., Jagannathan, K. et al. (2022) Associations between alcohol consumption and gray and white matter volumes in the UK Biobank. Nat Commun. 13, 1175.
[6] Immonen, S. et al. (2020) Moderate alcohol use is associated with decreased brain volume in early middle age in both sexes. Sci. Rep. 10, 13998.