People’s preference for either tea or coffee is rooted in their genes, according to a recent study.
If you serve brussels sprouts as a vegetable side dish at dinner, you’re likely to get a quick sense of which of your guests are coffee drinkers and which are tea lovers. The ones who find sprouts bitter are more likely to drink coffee. Ones who do not detect the same bitterness will more likely be tea lovers.
It is all in their genes.
This finding was recently announced by Dr. Liang-Dar Hwang, co-author of an Australian study that analyzed the genetic information of 400,000 people in the massive UK Biobank database. They used results from a previous study of 2,000 Australians that identified “taste receptor” genes that detect bitterness. Each extra copy of the bitterness receptor increased the likelihood of a person’s being a heavy coffee drinker (four or more cups a day) by 20 percent and reduced the probability of his or her drinking tea.
The receptors respond to three dominant bitter components of coffee: caffeine, quinine, and the medicinal compound propylthiouracil. They evolved as defense mechanisms whose role is indicated in the title of a detailed survey of the genetics of taste and smell: “Poisons and Pleasures.” Any food or drink that we ingest may be either of these. Poisons are largely marked by bitterness. Spoiled or rotting foods tend to be sour in taste and disturbing in their smell.
Over many millennia our inherited genes have evolved taste receptors as alerts. While researchers do not have a clear picture of inheritability, impacts of culture and other factors, there is clearly a significant association between genes and coffee avoidance. It is a complex relationship. People in the sample who were most sensitized to the bitterness of quinine and PROP were 4 to 9 percent more likely to be heavy tea drinkers than the average person. While the overall genetic message seems to be “bitterness is bad,” a little is attractive, and more pleasure than poison. Dr. Kwang conjectures that people who are better at detecting caffeine levels are more receptive to its noted stimulant effects and prefer it over tea, which is far lower in caffeine.
The finding is valuable for being based on a large and reliable sample; earlier studies with small cases and limited metrics had produced inconsistent results. The growing body of solid research suggests that around 40 percent of the coffee-tea preference gap is explained by genetic factors. Of course, that leaves 60 percent unaccounted for.
Much of the variance is cultural, psychological and lifestyle-related. But, factor in the genetic factors and caffeine may or may not be biologically comfortable and suitable for you for no other reason than you are your genes. The taste of coffee may also be not quite right for you – you are too sensitive, don’t discriminate well, and much prefer tea where you bring different sensitivities and discriminations.
“I love tea/coffee” or “I just can’t stand the taste” of one or the other because “it is too bitter” is not just an opinion – it may be the voice of your genes.