People sensitive to caffeine's bitterness drink more coffee: Study

People who are more sensitive to coffee's bitter taste actually drink more of the brew, a study suggests.

The study, published in the journal Scientific Reports, found that the sensitivity is caused by a genetic variant.

"You'd expect that people who are particularly sensitive to the bitter taste of caffeine would drink less coffee," said Marilyn Cornelis, assistant professor at Northwestern University in the US.

"The opposite results of our study suggest coffee consumers acquire a taste or an ability to detect caffeine due to the learned positive reinforcement (ie stimulation) elicited by caffeine," Cornelis said.

"People who have a heightened ability to taste coffee's bitterness -- and particularly the distinct bitter flavour of caffeine -- learn to associate good things with it," she said.

In the study population, people who were more sensitive to caffeine and were drinking a lot of coffee consumed low amounts of tea.

The study also found people sensitive to the bitter flavours of quinine and of PROP, a synthetic taste related to the compounds in cruciferous vegetables, avoided coffee.

For alcohol, a higher sensitivity to the bitterness of PROP resulted in lower alcohol consumption, particularly of red wine.

"The findings suggest our perception of bitter tastes, informed by our genetics, contributes to the preference for coffee, tea and alcohol," Cornelis said.

Scientists applied Mendelian randomisation, a technique commonly used in disease epidemiology, to test the causal relationship between bitter taste and beverage consumption in more than 400,000 men and women in the UK.

The genetic variants linked to caffeine, quinine and PROP perception were previously identified through genome-wide analysis of solution taste-ratings collected from Australian twins.

These genetic variants were then tested for associations with self-reported consumption of coffee, tea and alcohol in the current study.

"Taste has been studied for a long time, but we don't know the full mechanics of it," Cornelis said.