Whether it’s taken black, with milk and sugar, or served over ice, the United States spends about $40 billion every year on coffee. About 54% of all American adults drink coffee every day, averaging 3 cups daily. This caffeine-guzzling has led to the discovery of six new genetic variants that help explain the effect of coffee on the human body, and could explain why caffeine affects people differently. The research was led by Marilyn Cornelis of Harvard University and the results were published in the journal Molecular Psychiatry.
The study performed a genome-wide analysis of over 120,000 individuals with European or African American ancestry who regularly drink coffee. They found eight genes with variants that are connected to coffee consumption, six of which are new. Four of the genes influence the metabolism of caffeine, though Cornelis had already identified two of them in previous research. Two of the newly discovered genes are related to the psychoactive aspects of coffee and the final two are involved with fat and sugar metabolism, though it has not been made entirely clear how it is connected to the coffee.
"Coffee and caffeine have been linked to beneficial and adverse health effects. Our findings may allow us to identify subgroups of people most likely to benefit from increasing or decreasing coffee consumption for optimal health," said Marilyn Cornelis said in a press release.
Genetic variants that impact how coffee affects the body could help explain why some people feel great and alert after just one cup of coffee, while others need several cups to get going. Additionally, it might explain why some people feel more of a diuretic or laxative effect. The fact that six new variants were discovered at once presents an amazing opportunity to continue along the same vein of research.
"The new candidate genes are not the ones we have focused on in the past, so this is an important step forward in coffee research," said Cornelis.
These genetic variant predispositions account for roughly 1.3% of coffee drinking behavior, which is on par with how much genetics affect other habits like alcohol and tobacco use.
"Like previous genetic analyses of smoking and alcohol consumption, this research serves as an example of how genetics can influence some types of habitual behavior," added Daniel Chasman, one of the paper’s senior authors.
Going forward, the team would like to find any other genes that help influence how caffeine is metabolized. They would also like to identify genetic links to other compounds within coffee, such as the antioxidant chlorogenic acids, which are chiefly responsible for its trademark bitter taste. Identifying as many genes associated with coffee as possible will allow consumption habits to be customized to the individual, in order to get the most of the benefits while avoiding the drawbacks.
“The next question is who is benefitting most from coffee,” Cornelis told Harvard Gazette. “If, for example, caffeine is protective, individuals might have very similar physiological exposure to caffeine, once you balance the metabolism. But if coffee has other potentially protective constituents, those levels are going to be higher if you consume more cups, so they might actually be benefitting from non-caffeine components of coffee. So it’s a little bit complex.”