Does coffee make you feel sleepy?

Does coffee make you think of Pret, Starbucks or sleep? If caffeine makes you feel tired it might be because of a mutation in your caffeine receptors.

There’s a divide in the coffee world, and it’s not Pret vs Starbucks. It’s between people who break down caffeine quickly and those that break it down slowly.

The caffeine in coffee keeps you alert by blocking receptors in the liver that usually take up the sleep molecule adenosine, because they both share a similar shape.

Depending on your metabolism, i.e. if you have a 'rapid' or 'slow' liver enzyme CYP1A2, it could then take anywhere from 2 to 8 hours to remove half the caffeine in your blood.

This CYP1A2 enzyme influences your body’s sensitivity to caffeine. So that people with a fast metabolising mutation break down caffeine more quickly - those adenosine receptors become free again more often - allowing the sleep inducing chemical adenosine to bind and make you feel more tired than a slow metaboliser.

Why should I care?

Well, drinking coffee has also been linked with the reduction of several chronic diseases, particularly relating to the liver and kidneys, where it is processed by the body.

So, for example, if you're a fast metaboliser it's good to know that studies which observed coffee drinking habits in the population strongly indicate that drinking around 2-3 cups of coffee will reduce the risk or severity of liver damage. For the slow metabolisers, it's best to limit your intake to 1 coffee a day to keep the doctor away.

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Sources:

Rasmussen, B., Brix, T.; Kyvik, K., and Brøsen,K (2002). The interindividual differences in the 3-demthylation of caffeine alias CYP1A2 is determined by both genetic and environmental factors. Pharmacogenetics 12(6):p 473-478.

Rodenburg, E.M., Eijgelsheim, M., Geleijnse, J.M., Amin, N., van Duijn, C.M., Hofman, A., Uitterlinden, A.G., Stricker, B.H. and Visser, L.E. (2012). CYP1A2 and coffee intake and the modifying effect of sex, age, and smoking. The American Journal of Clinical Nutrition, 96(1), pp.182–187. doi:https://doi.org/10.3945/ajcn.111.027102.