But First, Coffee—Unless You Are Genetically Disposed to Prefer Tea

Genetic variants that affect our sensitivity to certain bitter substances could play a part in determining our brew of choice, according to a new study

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‘Tis the season for cozy, warm drinks—and whether you reach for a steaming mug of tea or a hot cuppa joe could be determined by your genes, according to a new study.

More specifically, as Alice Klein explains in New Scientist, our beverage preferences seem to be influenced by our sensitivity to certain bitter substances: caffeine, quinine (a compound found in tonic water) and propylthiouracil, or PROP (a synthetic flavour related to the compounds in cruciferous vegetables, like kale). Interestingly, a heightened ability to taste these bitter substances did not always result in an aversion to them. People who have a greater genetic disposition to tasting the bitterness of caffeine, for instance, appear to be heavier coffee drinkers.

The new research, published in Scientific Reports, is based on two datasets: an Australian study of 1757 twins and their siblings, which isolated the taste receptor genes that influence our perception of bitter tastes, and data from 438,870 participants in the UK Biobank, a research initiative that collected genetic information from more than 500,000 people in England, Scotland and Wales. Participants in the survey were also asked questions about how much coffee, tea and alcohol they drink.

When they analyzed the data, the researchers found that people with gene variants that make them taste caffeine strongly are 20 percent more likely to become “heavy” coffee drinkers—which, according to the study, means drinking more than four cups per day—than people with an average sensitivity to caffeine. And that’s somewhat surprising, because our ability to taste bitterness evolved as a defense mechanism, warning us to spit out substances that could be toxic.

“You’d expect that people who are particularly sensitive to the bitter taste of caffeine would drink less coffee,” says Marilyn Cornelis, senior author and assistant professor of preventive medicine at Northwestern University. But also at work is our learned ability to associate coffee’s bitterness with “good things,” like stimulation, Cornelis explains.

The researchers also discovered that people with genetic variants that heighten their sensitivity to quinine are four percent more likely to drink more than five cups of tea in a day. Those who are sensitive to the taste of PROP were nine percent more likely to be heavy tea drinkers.

These groups also drank less coffee than the caffeine-sensitive group, while the coffee-chuggers drank low amounts of tea. The forces at play here are not entirely clear; it is possible, for instance, that heavy coffee drinkers don’t consume much tea because they are so busy pursuing their caffeine fix. But study co-author Daniel Hwang tells Klein that the quinine and PROP-sensitive group might be more sensitive to bitter tastes, making them inclined to prefer drinks like tea, which has a subtler bitter flavor than coffee. The prop-sensitive group, in fact, was also less likely to drink alcohol, particularly red wine.

There are a number of drawbacks to the study. For one, it is based largely on self-reported data, which is not necessarily reliable. The analysis focused on individuals of white British ancestry, so it may not reflect drink preferences among other demographics.

Also, as study co-author Jue Sheng Ong tells Laura Geggel of Live Science, the research didn’t account for the flavorings—like cream and sugar—that people use to reduce coffee’s bitter taste. And beyond genetics, Ong acknowledges, “there are a lot of factors that determine a person’s coffee intake: socioeconomic status, ability to metabolize caffeine and smoking.”

Still, the study offers further evidence to suggest that while opting to have coffee or tea with your toast may not seem like a major decision, complex biological factors may play a part in shaping human taste. And that’s pretty sweet.

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