The most commonly used addictive drug in the world is coffee. A few decades ago, coffee was maligned as a substance that should be taken in low doses, if at all, because of the potential for deleterious effects, especially on the heart. But, over the past decade there is increasing evidence for a variety of health benefits when the ingestion of coffee is studied in populations.

But, with the advent of nutrigenetics, which looks at the science of the variety of genetic variations on dietary responses and nutrigenomics, which is the role of nutrients in gene expression, the position on coffee has clearly changed and is very much in the one size does not fit all category.

The human genome contains around 25,000 genes that code for around 150,000 proteins in the body. Logically, you would think that one gene codes for one protein but because of subtle movements in the DNA machinery, different proteins can be created depending on the position of DNA at the time. There are around 60 genes that dictate cardiac risk and in regard to the interaction between coffee and the cardiovascular system, there are four major genes that determine an individual’s response to coffee.

These genes include

1) CYP1A2

2) ADRA2B

3) ADORA2A

4) COMT

The actual designation of the genes is not really important unless you are a geneticist but it is important to realise firstly with CYP1A2 that there are two possibilities. One variation of this gene indicates that you are a fast metaboliser of caffeine and this is associated with reduced cardiovascular risk. The second variation of the gene indicates you are a slow metaboliser of caffeine, which is associated with a higher cardiovascular risk.

The second and third, AD genes, if the rather common mutations are present, then having a double espresso coffee will markedly increase your blood pressure. If however, you do not have these gene mutations, then coffee will have minimal effect on your BP.

Finally, COMT, which affects circulating and locally released adrenaline like hormones, if you have the genetic variation that gives you low activity in this enzyme system, then you will metabolise caffeine slowly and thus there is an increase in acute coronary events.

The bottom line with this discussion is that when genetic testing becomes more widespread, it is important that you have an understanding of your own personal mutations and if you are a coffee drinker with one of the riskier gene mutations, I would strongly suggest you switch to decaffeinated coffee. A standard cup of coffee purchased in a café as around 100 mg of caffeine. Decaffeinated coffee has only 8 mg and therefore the risk of any interactions with these abnormal genes is markedly reduced by drinking decaffeinated coffee.

With our increasing understanding of genetics, in the not too distant future (and, in fact there many good high quality genetic services already offering these tests), we will be able to gain a much better understanding of which nutrients are suited to a particular genetic make up and also which nutrients may affect your own particular gene expression. The same will be true for pharmaceutical drugs where there are already some basic tests available to gauge response to commonly used medications.

Until recently, the only way to determine your response to a particular food or medication is to trial the pill, test the benefits and assess the potential side effects. Fortunately, with these increasing advances in genetic screening, we are much closer to the vitally important field of personalised medicine.

Dr Walker is on the board of Imagene, a company that provides genetic screening services.