Marilyn Cornelis has been thinking about coffee for most of her life. As a child, Professor of Preventive Medicine at Northwestern University's Feinberg School of Medicine watched her father drop cup after cup – "a couple of pots a day" and made a game of daring his brothers to lick the spoon he used to stir. "It was so bitter for us," she says, her voice still registering some of the shock of twisting her face.
This reaction to bitter taste is universal, and encoded in our DNA – at a time when humans were constantly in need of food to sustain life, an aversion to bitter tastes kept people from stuffing poison into their mouths as they tried to avoid bitter taste. hunger. The humans who hated bitter tastes lived to get another day, which gave them the opportunity to generate offspring, who are currently in line at Starbucks.
Cornelis, whose academic research has focused on genetics and caffeine throughout her career, is sometimes among them, she admits, though it takes milk and sugar to get her to drink the bitter drink. "I still can not drink in black," she says. However, in a study published by Cornelis on Thursday, she and her colleagues at the QIRO Berghofer Medical Research Institute in Australia found that people genetically predisposed to being sensitive to the bitter taste of caffeine drink more coffee than those who are less sensitive or those that are sensitive to other bitter flavors, such as quinine.
Cornelis says the discovery was surprising. "Normally, humans avoid bitter tastes, and caffeine is one of those compounds, but people who were genetically sensitive to the taste of caffeine actually drank more coffee, so it may be that when you try caffeine, to the stimulating effects of caffeine. "
In other words, the urge for the stimulating effects of caffeine is so strong that we are willing to seek a bitter taste to get it.
This stimulant-seeking behavior is controlled by different genetic variants – those that control the body's ability to metabolize caffeine. If your genes are programmed to metabolize caffeine efficiently, you will burn your stimulant effect more quickly, which is why you will spend more time in the office coffee machine than colleagues. "We're all constantly titling our own levels of caffeine," says Cornelis.
She and other researchers have identified about eight genetic variants that act on caffeine metabolism and, as a result, predict levels of consumption. But a genetic test for coffee addicts is not what researchers are looking for. Instead, the study of caffeine and genetics may one day reveal some of the mysteries of the protective effects of caffeine on general health and diseases such as diabetes and heart disease.
Large-scale studies have shown a link between life expectancy and coffee consumption – people who drink about four cups a day live longer and, as scientists work to understand these effects, may be able to take advantage of this knowledge to fight disease.
The genetic link to bitter flavors has also been studied carefully. Scientists have shown that super-tempters, who have more taste buds and actually taste everything more vividly than the rest of us, tend to avoid strong seasoning and have a strong aversion to bitter. On the other hand, there are some outliers who express a true taste for bitter tastes (versus a learned tolerance). Correlations have been shown between this affinity for bitter tastes and "malevolent traits associated with a psychopathic personality, particularly the characteristic known as" everyday sadism ", writes Brown University neuroscientist Rachel Herz.
Herz's book, "Why You Eat What You Eat" explores the intersection of science and eating habits, and also points out that the enjoyment of bitter tastes has implications for drinking and vulnerability to alcoholism. A study from Indiana University showed that beer drinkers experienced the release of dopamine that mimics the feeling of being intoxicated simply by tasting bitter taste like beer. It's a classic Pavlovian response: transferring the response to beer for a simple taste. Study participants with a family history of alcoholism experienced an even greater release of dopamine from the bitter taste, signaling a genetic predisposition to expect reward for bitter tastes.
Most of us who are queuing for coffee, however, have no affinity for bitter tastes. Part of the cafeteria draw can be explained by cultural and even weather considerations – people in cold climates tend to drink more coffee.
Chicago, a cold winters 'advertising town, has always been a major consumer of coffee (we were Starbucks' first expansion store in 1987), and this is nothing compared to places like Finland where coffee consumption per capita is twice greater than the US
But Cornelis (who never drank coffee until moving to Chicago) says his research simply shows that those who are sensitive to the taste of caffeine are naturally tuned in to find it in an effort to get an extra burst of energy. They may still enjoy the taste of something sugary – which brings us back to the cafe.
The genius of Starbucks, says Cornelis, is not that it is perfectly positioned to take advantage of human genetics or eras of acquired experience. "Where Starbucks is really inserted," she says, "is that the bitterness of coffee can be easily masked. So they're always coming out with a new drink, a new flavor." Caffeine is what we all seek, but for most of us, there is only one question that matters, it says, "It's all about – what else do you want in your drink?"