Coffee and our love/hate relationship with bitterness
- Humans’ reaction to bitter taste is a protective mechanism to avoid eating poisonous food
- Sensitivity to caffeine can override the aversion to bitterness and make coffee lovers seek out bitter tastes
Marilyn Cornelis has been thinking about coffee for most of her life. As a child, the preventive medicine professor at Northwestern University Feinberg School of Medicine in Chicago watched her father down cup after cup – “a couple of pots a day” and made a game of daring her siblings to lick the spoon he used to stir it. “It was so bitter to us,” she says, her voice still registering a little of the face-twisting shock.
That reaction to bitter tastes is universal, and it’s coded into our DNA – when human beings needed to constantly seek food to sustain life, an aversion to bitter tastes kept people from jamming poisonous things into their mouths.
Humans who hated bitter tastes lived to forage another day, which gave them the opportunity to spawn descendants, who are currently standing in line at coffee shops.
Cornelis, whose academic research has centred on genetics and caffeine for her entire career, is sometimes among them, she admits, though it takes some milk and sugar to get her to down the bitter brew. “I still can’t drink it black,” she says.
Yet, in research published by Cornelis earlier this month, she and colleagues at the QIMR Berghofer Medical Research Institute in Australia found that people who are genetically predisposed to be sensitive to the bitter taste of caffeine drink more coffee than those who are less sensitive or those who are sensitive to other bitter tastes such as quinine.
