If it takes more than one cup of coffee to get you started in the morning, it may not be just tiredness that’s to blame.
Scientists say the need for caffeine is in our DNA, with a particular gene found among those who drink less coffee.
It is thought the gene, known as PDSS2, makes it harder for cells to break down caffeine, meaning it stays in the body for longer.
As a result, someone with the gene would need to drink less coffee to get the same buzz as someone without it.
The theory comes from a study by Edinburgh University scientists, who questioned more than 1,200 Italians on their coffee-drinking habits. The men and women also had their DNA read – and those who had the PDSS2 gene were found to drink around a cup of coffee less a day than the others.
A second analysis of 1,700 people from the Netherlands confirmed the result, although the effect of the gene on the number of cups consumed was slightly lower.
The scientists, who worked with researchers from the Italian coffee company Illy, said the difference could be down to the styles of coffee drunk in the two countries. In Italy, people tend to drink smaller cups such as espresso whereas in the Netherlands the preference is towards larger cups, which contain more caffeine overall.
Researcher Dr Nicola Pirastu said: ‘The results of our study add to existing research suggesting that our drive to drink coffee may be embedded in our genes.’
Caffeine is the world’s favourite stimulant, with nearly 90 per cent of adults regularly eating or drinking it in some form.
Britons alone get through some 70 million cups of coffee a day and 165 million cups of tea. It is thought the number of Britons with and without the gene is split fairly evenly, with half having a coffee habit and half easily turning down a second cup.
Dr Pirastu suspects he has the cup-after-cup version. ‘I am one of the few geneticists who hasn’t had my DNA read – but I do drink lots of coffee,’ he said.
‘I can drink it before I go to bed and it has no effect on me.’
The researcher previously found another gene that is carried by people who say they like coffee more. However, these people don’t drink more coffee than others and Dr Pirastu believes that our coffee habit, or lack of it, has got more to do with the effect of caffeine than the way it tastes.
He added: ‘This study reinforces the idea that genetics play a very important role in our everyday habits and lifestyles and understanding this is helping us not only know how people behave but also why, which will allow us to understand how to act on them.’
The research, detailed in the journal Scientific Reports, could shed new light on how coffee seems to ward off certain diseases, including Parkinson’s and some cancers.
Plus, some of the chemistry involved in the breakdown of caffeine is involved in the metabolism of medicines. So understanding the process could help doctors understand why some patients respond better to drugs than others. – Daily Mail