Drinking less coffee may be down to a genetic variant, researchers suggest.
Study co-author Dr. Nicola Pirastu, from the Usher Institute at the University of Edinburgh in the United Kingdom, and colleagues publish their findings in the journal Scientific Reports.
But while some people are happy with a never-ending supply of the hot stuff, others are content with a single cup of coffee to wake them up in the morning.
Previous research has suggested these disparities in coffee consumption may be down to differences in the way a person's body responds to caffeine - the main stimulant in coffee - but precisely what is behind these differences has been unclear.
Some studies have suggested certain genes may play a role; a 2014 study published in the journal Molecular Psychiatry, for example, identified a number of genetic variants associated with caffeine metabolism.
Now, Dr. Pirastu and colleagues say they have identified another genetic variant that may explain why some people drink less coffee than others.
One less cup of coffee daily with PDSS2 DNA variation
To reach their findings, the team analyzed the genetic data of 1,213 people from Italy. Of these, 843 were from six villages across north-east Italy, while 370 were from a small village in south Italy.
All participants completed a survey that disclosed how many cups of coffee they drank each day.
The team found that coffee consumption was lower for subjects who had a DNA variation in the PDSS2 gene; they drank an average of one less cup of coffee daily, compared with those who did not have the PDSS2 DNA variation.
In a further study of 1,731 individuals from the Netherlands, the researchers were able to replicate their findings, though they note that the effect of this gene variant on reduction of coffee consumption was not as strong.
The team speculates that this might be due to differences in coffee drinking styles between the two populations; people from Italy tend to consume smaller cups of coffee, such as espresso, while individuals from the Netherlands are more likely to drink larger cups of coffee that contain more caffeine.
Explaining the possible mechanisms behind their findings, the researchers suggest that the DNA variation in the PDSS2 gene lowers cells' ability to break down caffeine following coffee consumption, prolonging the amount of time the stimulant remains in the body.
As a result, individuals with this genetic variant do not need to drink as much coffee in order to get the same caffeine hit as those without the variant.
"The results of our study add to existing research suggesting that our drive to drink coffee may be embedded in our genes. We need to do larger studies to confirm the discovery and also to clarify the biological link between PDSS2 and coffee consumption."
Dr. Nicola Pirastu
The authors note that Italian coffee company Illy took part in the study, but they did not provide any funding.