Your preference for tea or coffee could be down to a genetic predisposition to perceiving bitterness, a new study has found.
Researchers from Australia, the USA and England found that people with a specific genetic variant that increases sensitivity to the bitter flavour of caffeine are more likely to be coffee drinkers. Conversely, tea drinkers more commonly have genetic variants that increase their sensitivity to the bitterness of other chemicals.
Dr Marilyn Cornelis of Northwestern University in llinois, who led the analysis, said: 'The study adds to our understanding of factors determining beverage preferences – taste, in particular – and why, holding all other factors constant, we still see marked between-person differences in beverage preference as well as the amount we consume.'
The study, published in Scientific Reports, analysed data from two sources. The first was a large twin study of people with European ancestry, which found certain genetic variant that are linked to the perception of different bitter tastes.
Of these variants, one in particular was associated with higher ratings of bitterness for caffeine, while two others were linked to perceiving the bitterness of quinine – most commonly found in tonic water – and a synthetic drug called propylthioracil (PROP), which is not normally found in food or drink.
The second data source was genetic data from the UK Biobank, of adults surveyed between 2006-2010. In addition, the database also includes participants' responses to health and lifestyle questions – including how many cups of different drinks they consume each day.
The team calculated a total score from their genetic variants predicting how strongly each participant tastes each of the three bitter chemicals, and compared this value to their reported beverage choices.
They found that people with a greater genetic predisposition to perceiving the bitterness of caffeine were 20 percent more likely to be heavy coffee drinkers. Those who drank less coffee were more likely to have the genetic variants associated with quinine or PROP perception.
Although the study has limitations – particularly as the participants self-reported their beverage preferences – the findings could shed light on the genetic and social factors that influence our food and drink choices.
Researchers had previously thought that those who are genetically predisposed to taste bitterness more intensely might avoid bitter drinks, but the findings of the study suggest this may not be the case. However, it may also be that those with a preference for coffee have learned to enjoy the bitter taste as a sign of the chemical buzz that caffeine gives.
However, the findings do challenge the view that bitterness is perceived as an indicator of poison. The conventional wisdom that 'bitter is always bad, let's avoid it' is an 'over simplistic' interpretation, Dr John Hayes, a taste researcher at Pennsylvania State University, who was not involved in the study, told Science News.