- Black coffee and a desire for bitter foods, such as dark chocolate, may be driven by genetic factors.
- According to a study, caffeine's natural bitterness is associated with psycho-stimulation.
- This is a learned effect – but more research is needed to support the finding.
If you like black coffee, scientists have news for you. It has little to do with the taste and a lot to do with your DNA.
This is according to a new study by researchers who wanted to gain insight into the role of taste in coffee-drinking behaviour.
Reporting on their findings in the journal Nature Scientific Reports, they explained that it’s not actually the taste you love, but the fact that your genes enable you to metabolise caffeine faster – and that you associate the bitterness with mental alertness.
A learned effect
In a news release, study co-author, professor Marilyn Cornelis, said the findings were “interesting”. Cornelis is an associate professor of preventive medicine and nutrition at the Northwestern University Feinberg School of Medicine in Chicago.
She added: "Our interpretation is that these people equate caffeine's natural bitterness with a psycho-stimulation effect. They learn to associate bitterness with caffeine and the boost they feel. We are seeing a learned effect. When they think of caffeine, they think of a bitter taste, so they enjoy dark coffee and, likewise, dark chocolate."
Dark chocolate, which also contains caffeine, is high in theobromine – an all-natural compound that's also a psycho-stimulant.
Types of coffee drinkers
Earlier research by Cornelis and her colleagues found that a genetic variant may be the reason why some people drink more cups of coffee a day than others.
Since dark coffee lovers metabolise caffeine faster, its stimulating effects wear off more quickly as well, which means they need to drink more, she explained.
But in the latest study, the team assessed different types of coffee drinkers. In their experiment, they separated black coffee drinkers from those who take cream and sugar.
For this study, they used genetic, dietary, and food preference data from the UK Biobank (a biomedical database) and two US cohorts.
"We found coffee drinkers with the genetic variant that reflects a faster metabolism of caffeine prefer bitter, black coffee," Cornelis said.
She added: "We also found the same genetic variant in people who prefer plain tea over sweetened, and bitter, dark chocolate over the more mellow milk chocolate."
Different health consequences
Cornelis explained that drinking black coffee versus coffee with cream and sugar has very different health consequences.
"The person who wants black coffee is different from a person who wants coffee with cream and sugar. Based on our findings, the person who drinks black coffee also prefers other bitter foods like dark chocolate. So, we are drilling down into a more precise way to measure the actual health benefits of this beverage and other food,” she said.
While the scientists have identified underlying biological mechanisms, they stressed that more research is needed to establish the causal role of coffee consumption in human health. Understanding determinants of beverage choice and consumption level is important to public health strategies, they wrote, considering that coffee is a highly consumed beverage worldwide.
Genetics behind preferences
Last year, a separate, first-of-its-kind study found that there was causal genetic evidence that cardio (heart) health influences one's coffee consumption, Health24 reported.
"... People subconsciously self-regulate safe levels of caffeine based on how high their blood pressure is, and this is likely a result of a protective genetic mechanism,” said the lead researcher Professor Elina Hyppönen at the University of South Australia.
A non-coffee drinker, or someone who drinks decaffeinated coffee, on the other hand, is more likely prone to the adverse effects of caffeine. As a result, they're more susceptible to high blood pressure, she said.
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