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People Sensitive To Caffeine's Bitter Taste Drink More Coffee, Study Finds (npr.org)
An anonymous reader quotes a report from NPR: A team of researchers conducted their analysis using data stored in something called the UK Biobank. More than 500,000 people have contributed blood, urine and saliva samples to the biobank, which scientists can use to answer various research questions. The volunteers also filled out questionnaires asking a variety of health-related questions, including how much coffee they drink. Part of what determines our sensitivity to bitter substances is determined by the genes we inherit from our parents. So the researchers used genetic analysis of samples from the biobank to find people who were more or less sensitive to three bitter substances: caffeine, quinine (think tonic water) and a chemical called propylthiouracil that is frequently used in genetic tests of people's ability to taste bitter compounds.
Then they looked to see if people sensitive to one or more of these substances drank more or less coffee than people who were not sensitive. To the researchers' surprise, people who were more sensitive to caffeine reported increased coffee consumption compared with people who were less sensitive. The result was restricted to the bitterness of caffeine. People sensitive to quinine and propylthiouracil -- neither of which is in coffee -- tended to drink less coffee. The effect of increased caffeine sensitivity was small: it only amounted to about two tablespoons more coffee per day. But by analyzing so many samples, the researchers were able to detect even small differences like that. The reason may be that people "learn to associate that bitter taste with the stimulation that coffee can provide," says one of the study authors.
Then they looked to see if people sensitive to one or more of these substances drank more or less coffee than people who were not sensitive. To the researchers' surprise, people who were more sensitive to caffeine reported increased coffee consumption compared with people who were less sensitive. The result was restricted to the bitterness of caffeine. People sensitive to quinine and propylthiouracil -- neither of which is in coffee -- tended to drink less coffee. The effect of increased caffeine sensitivity was small: it only amounted to about two tablespoons more coffee per day. But by analyzing so many samples, the researchers were able to detect even small differences like that. The reason may be that people "learn to associate that bitter taste with the stimulation that coffee can provide," says one of the study authors.
I suspect we can conclude nothing about bitter flavor and coffee preference from this other than they're correlated.
Stuff like this gets correlated all the time. It could be like red hair's correlation with altered pain perception; both are diverse effects of a single underlying mutation. Genetic variations with bitter tasting are also associated with trans-cellular membrane transport of certain classes of proteins that have effects throughout the body.
Or it could be that people learn to like the bitter flavor of coffee in the way that dogs learn to enjoy the sound of the dog trainer's clicker device. This is how people tend to crave foods that they habitually eat, even if they don't initially like those foods. The same goes for listening to music, which is why record companies do their best to saturate your experience with a new song. As long as they aren't conscious of being forced to listen to the song, the more they've heard a song the more they'll seek to hear it again.
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