Intriguing new research has revealed that people with a preference for drinking coffee over tea tend to display a genetic variant that signals a higher sensitivity to tasting bitterness in caffeine. This counter-intuitive finding suggests coffee drinkers develop a positive association with the bitterness of caffeine that reinforces their attraction to the beverage.

The study examined the genetic data of over 400,000 people, homing in on the association between three genes for bitter taste perception and a correlating preference for certain bitter-tasting beverages. The three bitter taste receptor genes studied were responsible for generating the bitter profiles in caffeine, quinine and propylthiouracil (PROP), a synthetic bitter profile similar to that tasted in cruciferous vegetables such as brussel sprouts.

The results of the study somewhat surprised the researchers, with people most sensitive to the bitter profile of caffeine reporting the most significant levels of coffee consumption.

"You'd expect that people who are particularly sensitive to the bitter taste of caffeine would drink less coffee," says Marilyn Cornelis, senior author on the research. "The opposite results of our study suggest coffee consumers acquire a taste or an ability to detect caffeine due to the learned positive reinforcement (i.e. stimulation) elicited by caffeine."

However, the results were flipped when the researchers examined subjects carrying the bitter taste receptors for quinine and PROP. This suggests those subjects most sensitive to an overall sense of bitterness ultimately preferred tea over coffee.

"Taste has been studied for a long time, but we don't know the full mechanics of it," says Cornelis, explaining the motivations behind the study. "Taste is one of the senses. We want to understand it from a biological standpoint."

The study was published in the journal Scientific Reports.