Tea or Coffee? Make a choice will help genes
Why do many people like the bitter taste, for example, black coffee? This may seem rather strange, because the bitterness of, say, plants, has always served as a signal warning ancient people about the presence of potentially harmful, and sometimes even toxic substances. According to evolutionary logic, a person should spit out such food or drink and never return to it.
The international team of scientists decided to find out why many people regularly and with pleasure use coffee (and without additives softening its taste like milk, sugar or lemon), while others, on the contrary, cannot stand this drink and prefer tea.
As a result, the researchers came to a curious conclusion. It turned out that the more sensitive a person is to the bitter taste of caffeine, the more invigorating drink he uses. In addition, sensitivity, in turn, is caused by special genes.
"One would expect that people who are particularly sensitive to the bitter taste of caffeine will drink less coffee. On the contrary, our research suggests that coffee lovers become addicted to caffeine because of the positive reinforcement, that is, the stimulation ", says lead author Marilyn Cornelis from Northwestern University in the United States.
The “counter-intuitive” conclusion of her team was made based on a large-scale experiment in which specialists studied the genetic data of more than 438 thousand people - men and women living in the UK. Experts used the information stored in the UK Biobank.
They analyzed data from surveys of people who noted how many cups of tea and coffee they drink daily. In addition, the researchers took into account data on the use of alcohol, because it also has a bitter taste.
The authors used the Mendelian randomization method, which is usually used by epidemiologists to identify causal relationships between variants of genes, their functions and the development of diseases.
In this case, with the help of Mendelian randomization, scientists were looking for causal relationships between bitter taste and consumption of beverages. In particular, the presence of specific genes of the so-called bitter taste receptors was analyzed.
Earlier, Australian researchers identified three genetic variants related to the perception of caffeine, quinine (often found in tonic drinks) and propylthiouracil (PROP), a synthetic compound resembling bitter substances found, for example, in Brussels sprouts. Natural bitter ingredients in coffee and tea can cause the same taste responses as the last two compounds.
The authors of the new work looked for already known genetic variants in humans and compared them with data on taste preferences.
As a result, it turned out that people with caffeine genes drink much more coffee than others (four or more cups a day), and rarely make a choice in favor of tea. At the same time, each additional copy of the gene that increases the sensitivity of caffeine receptors to taste, by 20% increases the likelihood that a person will consume more coffee, the authors noted.
According to them, caffeine gives an invigorating drink not only bitterness, but also other qualities like a characteristic texture and rich taste. Therefore, coffee lovers more subtly feel its taste, strength and aroma.
Meanwhile, people who are sensitive to quinine and PROP avoid coffee and more often prefer tea. Each copy of the quinine gene and the propylthiouracil gene increases the likelihood that a person will love tea by 9% and 4%, respectively (on average, tea lovers with such genes drink five or more cups a day).
It also turned out that hypersensitivity to the bitterness of propylthiouracil causes people to avoid alcohol, especially red wine.
In the future, the researchers intend to find out whether the presence of specific variants of the so-called taste genes influence a kind of dependence on a particular drink. In particular, we are talking about excessive consumption of coffee or tea, which can adversely affect health (although in moderation both drinks are beneficial).
At the same time, people's taste preferences may change with age. In addition, while it is not known what role the "genes of taste" play in these processes.
It is also possible that the new data on the perception of the taste of alcoholic beverages, will help specialists in the study of the nature of alcohol dependence.
"The sense of taste has been studied for a long time, but we do not know its complete mechanics. We want to understand it from a biological point of view," concludes Cornelis.
More details about this work are described in an article published in the journal Scientific Reports.