Do you prefer drinking coffee or tea? Scientists have found the answer may in fact come down to your genes.
The reasoning is all about our genetic predisposition to bitterness - in short, whether we find some substances more bitter than others will put us in one particular hot drink camp.
Both drinks contain bitter caffeine components that contribute to their pleasant taste (and energy-inducing effects) but coffee has an additional molecule called quinine - also found in tonic water.
Previous studies have found that people taste bitter flavours like caffeine, quinine and an artificial substance called propylthiouracil differently according to the types of taste receptor genes they have.
The new study, from the University of Queensland in Australia, looked at whether this variation in taste receptor genes affected our preference for a cuppa or a cup of joe.
Studying the taste receptor genes of 430,000 men and women in the UK (aged between 37 and 73) Daniel Hwang and his team made the participants drink both types of beverage and judge the strength.
The participants with gene variants that made them taste the caffeine more strongly, known as caffeine “super-tasters”, were 20 per cent more likely than the average person to be heavy coffee drinkers.
Heavy coffee drinkers were those who drank more than four cups a day. And these people were also less likely to drink tea.
This may be because people who are better at detecting caffeine are more prone to becoming addicted to its effects, and coffee contains more caffeine than tea. But future studies need to establish that more clearly, says Hwang.
In contrast, participants with genes that made them more sensitive to the taste of quinine and propylthiouracil were 4-9 per cent more likely than the average person to be big tea fans, meaning they drank more than five cups per day.
And in the same ways as the coffee drinkers not drinking tea, the tea drinkers were also less likely to drink coffee.
It’s unclear why exactly this is the case, but it may be because super-tasters of quinine and propylthiouracil – which are both more bitter than caffeine – are more sensitive to bitter tastes overall.
So they may find the intense bitterness of coffee overwhelming and prefer the gentler bitterness of tea, Hwang says.
The NHS recommends an upper limit of 400mg (about four cups) of caffeine per day for adults (300mg, or three cups, for pregnant women).