‘Java genes’ explain why coffee doesn’t work for some people


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Many studies that investigated coffee behavior found the brew doesn’t affect everyone the same. While there’s indeed such a thing as a caffeine tolerance, some people simply can’t get wired with coffee. Conversely, other people stay awake the whole night if they have a single cup of joe before bed time. Now, a new study has identified a set of genes involved in metabolizing coffee which explains why not everyone reacts to the drink equally — and this might actually have clinical implications.

The study was led by Marilyn Cornelis, assistant professor in the Department of Preventive Medicine at Northwestern University Feinberg School of Medicine. Cornelis previously identified gene variants which were associated with enjoying coffee more. This time, Cornelis and colleagues sampled the blood of participants who had drunk coffee earlier and studied their metabolites — intermediate products of metabolic reactions catalyzed by various enzymes that naturally occur within cells. The fewer metabolites you have in your blood, the faster your caffeine metabolism is.

“Each of us could be potentially responding to caffeine differently, and it’s possible that those differences can extend beyond that of caffeine,” Cornelis said.

By cross-screening these caffeine metabolites with the genetic makeup of each participant, the researchers were able to identify a set of genes involved in metabolizing coffee. Among them were gene variants which were previously associated with coffee-related behavior, but also a few new ones.

One gene called CYP2A6 was previously linked to smoking behavior and nicotine metabolism — now it’s related to caffeine metabolism as well. Another gene called GCKR was previously repeatedly linked to glucose and lipid metabolism in independent studies.

New genes that metabolize caffeine also coded for proteins involved in metabolizing important drugs, like those used to treat insomnia, Parkinson’s disease, and more. It’s not clear how important this is, but this is not the first time the metabolization of caffeine, nicotine, and other drugs seem to overlap.

“This makes sense, conceptually, but the genetic research confirms it and further re-emphasizes the notion that not everyone responds to a single cup of coffee (or other caffeinated beverage) in the same way,” Cornelis said.

“It’s important to know, given coffee has been implicated in so many diseases.”

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