Coffee habits: Study reveals genetic and environmental factors shaping consumption and health risks

US and Canada-based researchers have found statistical evidence that coffee drinking is a heritable trait, with particular gene variants inherited from parents influencing how much coffee one is likely to consume. Previous studies have hinted at genes impacting people’s coffee drinking habits. Scientists at the Schulich School of Medicine & Dentistry at Western University and the University of California San Diego (UCSD) used genetic data from a 23andMe database to compare coffee consumption characteristics. The study, published in Nature, used self-reported coffee consumption statistics to understand the links between the genes that are known to be associated with coffee consumption and the traits or conditions related to health. “We used this data to identify regions on the genome associated with whether somebody is more or less likely to consume coffee, and then identify the genes and biology that could underlie coffee intake,” says Hayley Thorpe, lead author and postdoctoral researcher at Western’s Schulich Medicine & Dentistry. Abraham Palmer, the study’s lead researcher and a professor at the UCSD School of Medicine Department of Psychiatry, notes that most people are surprised to learn that habits and genetics are linked to coffee consumption. “We weren’t surprised to find that in both cohorts we examined, there was statistical evidence that this is a heritable trait. In other words, the particular gene variants that you inherit from your parents influence how much coffee you’re likely to consume.” Is coffee good or bad for you? The second question the paper seeks to address is whether drinking coffee is good or bad for health. To probe this, the researchers compared the genetic data from 23andMe with a similar UK Biobank database of 334,649 individuals. They found that the answer is not definitive. The comparison revealed consistent positive genetic associations between coffee and risk-associated health outcomes such as obesity and drug usage. The researchers explain that a positive genetic association represents a link between a specific gene variant (the genotype) and a specific condition (the phenotype). On the other hand, a negative genetic association is a purported protection quality that discourages the development of a condition. This does not imply that a coffee drinker is likely to use other substances or become obese but suggests that the genetic predisposition for coffee intake is related to these characteristics. “Look at the genetics of anxiety, for instance, or bipolar and depression: In the 23andMe data set, they tend to be positively genetically correlated with coffee intake genetics,” Thorpe points out. “But then, in the UK Biobank, you see the opposite pattern, where they’re negatively genetically correlated. This is not what we expected.” Differences in results There are other instances where the data from 23andMe didn’t align with the UK Biobank, but the differences were most notable in psychiatric conditions, Thorpe further explains. The surveys did not account for how people consume coffee beyond the decaffeinated version.“It’s common to combine similar datasets in this field to increase study power. This information paints a fairly clear picture that combining these two datasets was really not a wise idea, and we didn’t end up doing that.” She notes that combining the databases might conceal effects, leading the research to false conclusions — or results that cancel each other out. Sandra Sanchez-Roige, an associate professor in the UCSD School of Medicine Department of Psychiatry, says the researchers know how the results differed. In some instances, the questions posed in both surveys differed in some instances, making the comparison vague. For example, the 23andMe survey asked: “How many cup-sized servings of caffeinated coffee do you consume each day?” On the other hand, the UK Biobank’s question on coffee consumption was: “How many cups of coffee do you drink each day, including decaf?” The surveys did not account for how people consume coffee in both locations beyond the decaffeinated version. For example, Thorpe explains that while the UK has an appetite for instant coffee, coffee drinkers in the US prefer ground beans. “Then there are the frappuccinos,” Sanchez-Roige adds, invoking the popular American way of having coffee loaded with added sugar and other sugar-laden flavored additives. But what is interesting about the survey, the researchers say, is that it reflects how different consumers drink coffee across cultures. Future research Palmer states that genetics shape a lot of things, like height. “And those kinds of things probably would play out very similarly whether you lived in the US or the UK. But coffee is a decision that people make.” This implies that a person in the US with a given genotype might have a different phenotype than someone living in the UK. “And that’s really what the data tell us,” says Sanchez-Roige. “Because unlike height, where your behavior doesn’t really have much to do with it, your behavior and the choices you’re making in your environment play out in various ways. So the interaction between genotype and environment complicates the picture.” The scientists urge more investigation to decode the relationships between genetics and the environment, highlighting that further research can include substance-use issues.