We often hear in the media that a little bit of alcohol in our diet is good for heart health. That’s what the mediterranean diet is all about, right? But recent data suggests this is wrong, and that in actual fact any alcohol in our diet is bad for heart health. So what on earth is going on with alcohol research? More to the point, what – and how much – should we be drinking?
First off, it is important to highlight that the recommended alcohol intake in the UK at the moment is no more than 14 units per week. Any more than that and it’s believed you are causing harm to your body. The current 14 units per week recommendation is equivalent to seven pints of 3.5% beer (see the units of alcohol table below), obviously an amount that should be divided up across the week and not consumed in one go. This being the UK, of course, there are many people that will happily attempt to drink 14 units in a single evening. Is there a sensible measure for the ‘right amount’? If too much alcohol is bad for our health, then why are people saying that a little bit of alcohol is good for our health?
Over the past two decades research has been conducted that suggests that those people who have a small amount of alcohol in their diet, equivalent to one to one-and-a-half glasses of an alcohol drink have a reduced risk of heart disease when compared to those people who do not drink any alcohol. On the other hand, those people who drink more than five glasses of alcohol a day (more than 60 g per day of alcohol, or eight units) have a significantly increased risk of heart disease, as well as other diseases linked to alcohol including cancers, liver disease and issues with mental health. This relationship between alcohol intake and heart health has been referred to as the “J-shaped curve” – no alcohol intake has an increased risk of heart disease, moderate intake lowers this risk, and a high intake significantly increases the risk above that of no alcohol intake.
The alcohol and heart health J-shaped curve was introduced from a number of epidemiological studies over the past two decades, but recent data published in the new guidance from the Scottish Intercollegiate Guidelines Network for the first time questions the J-shaped curve relationship. Let’s have a look at this new research, then.
The current J-shaped research is based on epidemiological studies. These studies are done as it is very difficult to run studies where one group consumes no alcohol, or maybe a placebo control for 10 years, and another group drinks alcohol for 10 years. The controlled studies are known as randomised controlled trials. So a way of getting around this is to basically interview a very large group of people (more than 1000 people at a time) and then follow them for five to 10 years. Over this time, lots of measurements and questions are asked. This allows scientists to measure what impact alcohol has on someone’s health.
It is these studies that have been used to establish this J-shaped curve relationship for alcohol to date. However, as you can probably imagine, there could be lots of different factors that could alter the outcome of someone’s health over 10 years. These factors are known as cofounders. Now, there are a number of clever ways of controlling for these use in statistics, as well as controlling the type of people that are recruited into the study. But, fundamentally, it is impossible to remove all cofounders.
Now this is where the limitation lies with the J-shaped curve relationship with alcohol and heart health. Scientists believe that that the cited cardio-protective effect of alcohol may be due to methodological flaws in the evidence. Hence, those people who are recruited into the epidemiological studies who do not drink alcohol are at risk of being ‘sick quitters’ of alcohol. As such, they do not drink alcohol as they may already be ill or actually feel more ill when they drink. Therefore, the non-alcoholic group that has been recruited in these studies may be skewing the final conclusions of the study.
In order to account for this flaw in the evidence, a study published in the British Medical Journal randomised all of the previous data published on alcohol intake and heart health (using something called Mendelian randomisation), including 56 epidemiological studies with a total of 261,991 participants. But the difference here is that they used genetic screening to assess those people who were carriers of the rs1229984 variant in the enzyme gene that breaks down alcohol, known as alcohol dehydrogenase 1B gene (ADH1B). Expression of this gene variant has been associated with reduced consumption of alcohol due to unpleasant side effects. So those who expressed the variant of the ADH gene consumed 17.2% fewer units of alcohol per week and had a reduced rate of binge drinking and higher abstention of alcohol compared to non-carriers. The really interesting thing was that this group of people had lower blood pressure (systolic), reduced risk of hypertension, coronary heart disease and lower waist circumference and BMI.
Therefore, this data for the first time shows that alcohol consumption in any form, can increase the risk of heart disease. This data is highly valid as it reduces the risk of bias and confounders due to using a genetic marker instead. Currently though this data is not well known and is not being communicated to the medical community for application and role out to the UK population.
The general guidance off the back of this new data is drinking less is better for your health. You should aim to try and keep drinking each day to a minimum. Use non-alcoholic drinks to swap in and out of your drinking on a night or a meal out to keep alcohol consumption to a low.
More data will be emerging soon to further support this new research. But for now, dodge alcohol from time to time to have a big impact on your health.
|Volume equivalent to one unit||Normal serve size in a pub / bar|
|Beer / lager||3.5%||0.5 pint||1 pint|
|Beer / lager||5.0%||0.35 pint||1 pint|
|Wine||10%||100 ml||125 ml (small)
250 ml (large)
|Wine||13%||77 ml||125 ml (small)
250 ml (large)
|Spirit||40%||25 ml||35 ml (single)
50 ml (double)
[Note: Unit of alcohol = ABV% x volume of alcohol in litres]