Expresso or Americano? Your genome has the answer

Since we were kids (unless under the spell of a creationist education), we have been told that genetics is the reason for the colour of our eyes, our hair, our height and whether we look more like mum or dad. In the last few years, it might seem to many that gene association studies have gone a tad far and that everything is due to genetics, one way or the other. Well, that is actually the truth. Even your ability to drink coffee is written in your genes. Want to see how?

According to recently published research ¹on nearly 3000 people in two very different countries in Europe (40% Italians; 60% Dutch), the activity of the gene PDSS2 determines the ability of people to endure caffeine, and therefore the amount of coffee they are able to drink. Specifically, the more active the gen the less coffee people can drink since activity of this gene lowers the levels of caffeine-degrading enzymes in the liver.

This study made use of the most advanced technology to sequence the genome, and after full genotyping of all individuals taking part in the experiment a genome-wide association study to the coffee drank/day was performed. On average, from the questionnaires the researches found that italians drink about a couple expressos per day while the dutch go up to more than 5 cups of american (filtered) coffee a day. In passing I’d like to say that given that what they drink in Holland is more dirty water than coffee, I am not surprised that they need to drink liters of it to feel something…and yet according to this and that study, I would be wrong: due to the bigger sizing of their coffees Dutch people would be consuming three times more caffeine per cup than italians.

Now, let’s focus on the results of the study, which differed depending on the population studied. While in the Italians up to 21 gene variants in regions close to the PDSS2 gene were found, and one of them had such a strong influence over coffee consumption that it altered the ratios by more than one cup of expresso a day (to put the result into perspective, remember that the average stood in 2 expressos/day). Conversely, among the Dutch only 5 of the variants found in the italians seemed to have an effect, and not a big one.

Since the Dutch’s caffeine intake is much higher than that of italians, the authors consider that other caffeine-processing genes like CYP1A2 might act at higher caffeine doses, while PDSS2 would be more restricted to control caffeine intake in those used to a low caffeine intake.

I find the results of the work really interesting, not just because it shows that even something as menial as coffee consumption is more or less written in our genes, but it also shows regional genetic variance that is, from my point of view, associated to different cultural/societal habits and stands as an example of cultural evolution.

Further reading:

Grigg, D. The worlds of tea and coffee: Patterns of consumption. GeoJournal 57, 283–294 (2002).

Goldstein, A., Warren, R. & Kaizer, S. Psychotropic effects of caffeine in man. i. individual differences in sensitivity to caffeine-induced wakefulness. J. Pharmacol. Exp. Ther. 149, 156–159 (1965).

Conterio, F. & Chiarelli, B. Study of the inheritance of some daily life habits. Heredity (Edinb). 17, 347–359 (1962).