Alcohol and the cardiovascular system
Drinking a little bit of alcohol regularly is cited by medical websites and common knowledge alike to be good for the heart. Sources talk about a light to moderate consumption of liquor being associated with a lower risk of ischemic strokes – in other words, strokes causes by a blockage of blood vessels in the brain.[1] As well as this, they explain how the so-called “good” cholesterol (high density lipoproteins) may be raised by a substantial consumption of alcohol.[2] This good cholesterol is linked with lower rates of heart disease, and better cardiovascular health all round. With all of this in mind, could we consider alcohol as being cardioprotective when drunk in small amounts? Should health professionals include a small amount of alcohol as part of their advice for building a healthy lifestyle? Mounting evidence over the last two decades is showing the contrary, with the validity of medical websites and common knowledge increasingly being called into question.
Amongst the research considering whether a moderate alcohol consumption is good for our hearts, one seminal review in 2001 ascertained that alcohol could slightly reduce the risk of coronary heart disease (CHD) in men.[3] This is due to ethanol, the primary component of alcohol, altering the properties of lipids (specifically those high density lipoproteins) and haemostatic factors (factors that help your body to clot bleeding). When combined, these alterations helped reduce the risk of CHD, as well as being moderated by favourable genetics. In other words, different people experienced a better or worse effectiveness of alcohol at reducing the risk of CHD, due to their genes. At this point in research two decades ago, there was still much about the specific mechanisms involved which was not understood. However, the review emphasizes that “evidence to support the cardioprotective effects of alcohol consumption among humans is abundant and strikingly consistent.” Despite this heartening praise of alcohol and cardiovascular health, even at this time, they did not recommend that alcohol consumption should be included within health guidance, but that it is perfectly fine when incorporated into a balanced lifestyle.
More recently, an in-depth review found slightly similar effects, but came to a different conclusion about how alcohol affects the cardiovascular system.[4] They were able to dissect the various influences of people’s behaviour, their genetics, and the natural biological variations between people affecting how cardioprotective alcohol is for them. Whilst these researchers acknowledged that light-moderate drinking of alcohol has some benefits for people’s cardiovascular health – such as mitigating some mechanisms involved in the development of atherosclerosis, which later leads to cardiovascular disease – they highlight some major faults with this understanding commonly accepted at the time. The first being the term ‘light to moderate drinking’, given that “ascertaining the exact alcohol consumption threshold for determining both the benefit and risk has been challenging, and threshold levels continue to differ across studies.” In other words, there is no clear consensus on what ‘light to moderate’ drinking actually means – is that one drink a night? Less or more? And is it different for different genders? As well as this, any cardioprotective benefits alcohol may have are massively outweighed by the risks to people’s health. Just a few of the cardiovascular impacts of heavier and chronic alcohol consumption include: mitochondrial dysfunction, circulatory changes, inflammatory response, and in the worst cases, programmed (apoptic) cell death. Equally, many of the studies which show the positive impact alcohol can have on the heart are epidemiological studies. This is a research method which records the widespread distribution and determinants of cardiovascular ill health across specific populations. However, the gold standard for scientifically valid and reliable evidence is randomised control trials (RCTs), where people are randomly assigned to one of two trials (the experimental trial and the control trial) and the results between the trials are compared. Because none of this research uses RCTs and thus lacks validity, this study explicitly states that health professionals should not include alcohol in their advice for healthy lifestyle interventions. Therefore, we can see how understanding has begun to shift away from considering alcohol a cardioprotective factor in light-moderate doses, to seeing it as a substance which is still detrimental to cardiovascular health.
Furthering the conclusions of this study, a study conducted last year cemented that even light-moderate drinking is actually not cardioprotective at all – but is actually harmful.[5] They looked at this through the lens of atrial fibrillation, an irregular, fast heart rate which can lead to strokes and heart failure in the general population. Over 100,000 participants were followed by these researchers over a period of 28 years, to try and better understand the relationship between alcohol intake and atrial fibrillation. Participants recorded how much they drank – though this is a potential weakness, given people’s habit of intentionally underestimating their alcohol consumption to appear more socially acceptable. A better method, as suggested by the previous study, would be to use biomarkers to measure people’s exact blood alcohol concentration, therefore mitigating any tactical under-reporting.[6] Alongside this, participants were subjected to biomarker measurement – specifically N-terminal pro-B-type natriuretic peptide and high sensitivity troponin I – both of which are highly predictive of atrial fibrillation. Having accumulated this data about participants for almost three decades, this study found that even a light, habitual habit of drinking 1.2 drinks a day was associated with an increased risk of atrial fibrillation. Given the understandings about how atrial fibrillation can lead to more serious cardiovascular issues, such as strokes and heart failure, even the most light-moderate consumption of alcohol has the potential to be harmful. Thus, the understanding of alcohol as being cardioprotective is firmly refuted – and because of the longevity and large sample size of this study, this has resulted in a very strong analysis. It therefore goes without saying that alcohol should not be recommended by health professionals as part of a healthy lifestyle, as it is not conducive to good cardiovascular health.
Alongside this, another recent study really dissected the claim that light-moderate drinking can be cardioprotective.[7] Using a cohort study of 371,463 individuals, these researchers analysed genetic data in relation to those people’s consumption of alcohol and their rates of cardiovascular disease (CVD). Having compiled all of this data, they found an interesting effect. What effectively caused prior researchers to claim that light-moderate drinking was actually beneficial to cardiovascular health was finding the famous J-shaped curve in their research. In other words, consumption of alcohol shows a very small risk to cardiovascular health at low doses, to a sky-rocketing increase in risk with not much higher alcohol consumption, forming a ‘J’ shape on a graph. However, these researchers showed how light-moderate drinkers tend to have a healthier lifestyle than all other intensities of drinkers, even abstainers. As well as this, light-moderate drinkers also tend to have a higher socioeconomic status and education level, as well as other factors – all of which contribute to better cardiovascular and overall health. Therefore, when light-moderate drinkers are considered within their wider social context, any claims about light-moderate drinking showing positive effects on our cardiovascular health is essentially confounded. Not considering these kinds of contextual factors has been a common issue of medical and biological research into cardiovascular health. It is certainly moving to a more integrated understanding of people – not only biological, but social and psychological, and how these factors interact – but it has meant that invalid conclusions can be drawn when only biological mechanisms are considered with such a narrow focus. With all of this in mind, this study ultimately concludes that their findings “substantiate prior claims that no amount of alcohol is protective against cardiovascular disease.” They also open up avenues for future research, as the results point towards the relationship between alcohol consumption and cardiovascular disease as being due to some shared genetic component. Rather like the possible genetic influence affecting how much alcohol affects the risk of coronary heart disease in men[8], this study suggests that some are more vulnerable or protected against how impactful alcohol is on their cardiovascular health. This is certainly something which health professionals should tailor into their advice, once there is enough research and understanding to do so.
Ultimately, though alcohol was once considered – and is still referred to on medical sites – as slightly protective for our cardiovascular health in light-moderate consumptions, this has been largely disproved in recent years. Now understood to be linked to atrial fibrillation at very low alcohol doses, as well as other adverse cardiovascular effects, the validity of prior research has also been called into question due to the confounding effects of light-moderate drinkers’ lifestyles and social contexts. It is certainly the consensus that alcohol should not be recommended as slightly cardioprotective by health professionals, and yet it continues to endure on online medical sites and common knowledge. Future work can both aim to replace this with more up-to-date information, as well as investigating more closely the mechanisms at work between drinking alcohol and cardiovascular health.
References
[1] Mayo Clinic Staff. (2021) Alcohol use: Weighing risks and benefits. Mayo Clinic. Available at: https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/alcohol/art-20044551
[2] John Hopkins Medicine. (n.d.) Alcohol and Heart Health: Separating Fact from Fiction. John Hopkins Medicine. Available at: https://www.hopkinsmedicine.org/health/wellness-and-prevention/alcohol-and-heart-health-separating-fact-from-fiction
[3] Hines, L.M., Rimm, E.B. (2001) Moderate alcohol consumption and coronary heart disease: a review. Postgraduate Medical Journal. 77. 747-752. Available at: https://pmj.bmj.com/content/77/914/747
[4] Piano, M.R. (2017) Alcohol's Effects on the Cardiovascular System. Alcohol Res. 38(2). 219-241. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5513687/
[5] Csengeri, D., Sprünker, N.A., Di Castelnuovo, A., et al. (2021) Alcohol consumption, cardiac biomarkers, and risk of atrial fibrillation and adverse outcomes. Eur Heart J. 42(12). 1170-1177. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7982286/
[6] Piano, M.R. (2017) Alcohol's Effects on the Cardiovascular System. Alcohol Res. 38(2). 219-241. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5513687/
[7] Biddinger, K.J., Emdin, C.A., Haas, M.E., et al. (2022) Association of Habitual Alcohol Intake With Risk of Cardiovascular Disease. JAMA Network Open. 5(3). e223849. Available at: https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2790520
[8] Hines, L.M., Rimm, E.B. (2001) Moderate alcohol consumption and coronary heart disease: a review. Postgraduate Medical Journal. 77. 747-752. Available at: https://pmj.bmj.com/content/77/914/747