Genes may be a clue to your preferred brew

If you choose a strong, hot coffee over a nice cup of tea and a little lie down, science says you can blame your parents.

Great divide: the study indicated the more cups of coffee you have, the fewer cups of tea.

Would you like a cup of tea or coffee? As if your answer to this question did not already convey enough cues about class, age and social status, a new study has found that it also tells your host something else: your genetics.

Research has shown that your choice of hot drink is partly influenced by the genes that affect how we perceive bitterness. The same study also confirmed that the British population can broadly be divided according to the two beverages — the more cups of coffee you have, the fewer cups of tea.

A study by Jue-Sheng Ong, from the University of Queensland in Australia, published in the journal Scientific Reports, attributed this drinking divide in part to the same genes that control how strong bitter foods taste, although he conceded there was also another factor: “It’s very hard to drink a lot of both at the same time.”

The ability to taste bitterness is odd because it is controlled by very few genes. While some scientists believe that bitterness perception has evolved as a way to spot whether something is poisonous, the fact that a mutation in just a couple of genes can have a profound effect on it suggests it is probably not that useful for our survival.

This quirk also means that there are large differences in how the population taste bitter foods. For Mr Ong’s research, he looked at three specific bitter tastes: quinine, which is found in tonic water; propylthiouracil (prop), which is similar to molecules found in Brussels sprouts; and caffeine itself.

The ability to taste prop is known to be highly variable. About a quarter of the population perceive it as extremely bitter and are termed “supertasters”. Half of the population can taste it to some degree and are medium tasters. The final group, non-tasters, do not taste it at all.

Mr Ong and his colleagues looked at a group of 2000 people to work out which genes were associated with each of the tastes, including prop. Then they used the UK Biobank, which contains the genomes of 400,000 people, to see how these related to coffee and tea consumption.

“People that taste prop or quinine strongly in general have less coffee consumption,” said Mr Ong, a PhD student.

“This is consistent with the fact that biologically they have more bitter taste receptors on their tongue. Because of that elevated sensation of bitterness they turn away from coffee and maybe think it is way too bitter to handle. They opt for tea because that is less bitter compared to coffee.”

The effect was not big. The researchers said that on an individual level other effects such as social class or even whether you suffer from insomnia were likely to dwarf the influence of genes. Nevertheless, looking at such a large sample they showed the influence of genetics was consistent and significant.

However, prop and quinine were not the whole story. For caffeine, oddly, there was the reverse link compared with the other bitter tastes.

“What we see is if you have a higher ability to taste bitterness in caffeine, you end up drinking more coffee,” said Mr Ong.

He could not say why this was the case, but suspected it was a learned feedback mechanism based on the pleasure that people get from coffee. “If a person has the ability to taste the caffeine in coffee it reinforces this habitual consumption,” he said. “It may be that indirectly the taste becomes some kind of reinforcement.”

— The Times