Coffee Tastes Bitter, So Why Do People Drink It?

Coffee barista
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It may sound counterintuitive, but people who are supersensitive to coffee's bitter taste actually drink more of it, a new study finds.

This sensitivity isn't simply a matter of taste, either, but rather is influenced by a person's genetic makeup, the researchers said in the study, which was published online today (Nov. 15) in the journal Scientific Reports.

"You'd expect that people who are particularly sensitive to the bitter taste of caffeine would drink less coffee," study senior researcher Marilyn Cornelis, an assistant professor of preventive medicine at the Northwestern University Feinberg School of Medicine in Chicago, said in a statement. "The opposite results of our study suggest coffee consumers acquire a taste [for] or an ability to detect [the bitterness of] caffeine due to the learned positive reinforcement elicited by caffeine." [10 Things You Need to Know About Coffee]

Put another way, people who have a heightened ability to taste the bitterness of coffee, and especially the distinct bitter flavor of caffeine, learn to associate "good things with it," Cornelis said. This finding is surprising, given that bitterness often serves as a warning mechanism to convince people to spit out harmful substances, the scientists said.

Researchers conducted the study to understand how genetics influences people's consumption of tea, coffee and alcohol, which tend to taste bitter, said lead study researcher Jue Sheng Ong, a doctoral student in the Department of Genetics and Computational Biology at the QIMR Berghofer Medical Research Institute in Brisbane, Australia.

"While all bitter flavors might seem the same, we perceive the bitterness of Brussels sprouts, tonic water (quinine) and caffeine separately," Ong told Live Science. "The degree to which we find these flavors bitter is, in part, determined by your genes."

To investigate, the researchers looked at the genetic makeup and daily bitter-beverage consumption of more than 400,000 people from the United Kingdom. "Using the genes related to our ability to taste bitterness, we were able to assess whether those that have a higher genetic predisposition to tasting bitterness are more likely to prefer tea over coffee," Ong said.

The results showed that people with the genes to taste the bitterness of green vegetables (such as Brussels sprouts) or tonic water are more likely to prefer tea over coffee, the researchers found. In addition, people who were more sensitive to quinine's bitter flavors and those found in green vegetables tended to avoid coffee.

Meanwhile, people with the genes to taste the bitterness in Brussel sprouts were less likely to drink alcohol, especially red wine, than people without those gene variants, the researchers found. This insight may help scientists studying addiction, Ong said.

Ong noted that the researchers didn't look at flavorings, such as cream or sugar, that people sometimes pour into coffee to temper its bitterness. "One can imagine that, at a personal level, there are a lot of factors that determine a person’s coffee intake — socioeconomic status, ability to metabolize caffeine and smoking," he said. "On top of that, people drink all sorts of coffee — black coffee, flat white [and] cappuccino." So, the researchers chose to look for big trends in how genes relate to bitter-beverage consumption, he said.

"[The results] suggest that perhaps most types of coffee still share very similar bitter-taste profiles," Ong said.

Originally published on Live Science.

Laura Geggel

Laura is the archaeology and Life's Little Mysteries editor at Live Science. She also reports on general science, including paleontology. Her work has appeared in The New York Times, Scholastic, Popular Science and Spectrum, a site on autism research. She has won multiple awards from the Society of Professional Journalists and the Washington Newspaper Publishers Association for her reporting at a weekly newspaper near Seattle. Laura holds a bachelor's degree in English literature and psychology from Washington University in St. Louis and a master's degree in science writing from NYU.