Coffee is one of the most widely consumed beverages. In the fresh study, researchers from the University of California, San Diego, and elsewhere conducted a genome-wide association study (GWAS) of coffee consumption in 23andMe participants from the U.S. They examined genetic correlations and conducted a phenome-wide association study of hundreds of biomarkers, health, and lifestyle traits, then compared their results with the largest available GWAS study of coffee consumption from the UK Biobank.
“We collected genetic data as well as self-reported numbers of coffee consumption to assemble the GWAS,” said lead author Dr. Hayley Thorpe, a researcher at Western University and the University of Guelph.
“The idea was to make connections between genes known to be associated with coffee consumption and health-related traits or conditions.”
“We used this data to identify areas in the genome that were associated with whether someone was more or less likely to consume coffee.”
“Then identify genes and biological factors that may underlie coffee consumption.”
“Most people are surprised to learn that coffee consumption is influenced by genetic factors,” said co-author Dr. Abraham Palmer, a researcher at the University of California, San Diego.
“Based on previous publications, we had good reason to suspect that there are genes that influence the amount of coffee we drink.”
“So we weren’t surprised to find that in both cohorts we studied, there was statistical evidence that this was a heritable trait.”
“In other words, the specific gene variants you inherit from your parents affect how much coffee you’re likely to consume.”
“The genetic influence on coffee consumption was the first of two questions we wanted to address,” said senior author Dr. Sandra Sanchez-Roige, a researcher at the University of California, San Diego.
“The second thing is something that coffee lovers are really eager to learn. Is drinking coffee good or bad? Is it associated with positive health effects or not?”
The group’s genome-wide association study of 130,153 US 23andMe participants was compared with a similar UK Biobank database of 334,649 British people, revealing consistent positive genetic associations between coffee and harmful health outcomes such as obesity and substance employ.
A positive genetic association is an association between a specific gene variant (genotype) and a specific condition (phenotype).
Conversely, a negative genetic link is a apparent protective feature that discourages the development of the disease.
The results become more complicated when mental disorders are involved.
“For example, look at the genetics of anxiety, bipolar disorder, and depression: in the 23andMe data set, they appear to be genetically positively correlated with the genetics of coffee consumption,” Dr. Thorpe says.
“But in the UK Biobank you see the opposite pattern where they are negatively genetically correlated. This is not what we expected.”
“There were other cases where the 23andMe kit was not compatible with the UK Biobank, but the biggest discrepancies were for mental health conditions.”
“In this field, it is common to combine similar data sets to escalate research power. This information paints a pretty clear picture that combining these two data sets wasn’t really a shrewd idea. And ultimately we didn’t do it.”
“Combining databases can mask effects, leading researchers to erroneous conclusions — or even canceling each other out.”
“We have some ideas about how the differences in results came about. “For starters, the surveys were sort of comparing apples and pears,” Dr. Sanchez-Roige said.
“For example, the 23andMe survey asked, ‘How many 5-ounce (cup-sized) servings of caffeinated coffee do you consume each day?’ Compare that to the UK Biobank survey: ‘How many cups of coffee do you drink each day? (Including decaf coffee)?’”
“Aside from serving size and division into caffeinated and decaffeinated drinks, the studies did not take into account different ways of serving coffee.”
“We know that in the UK there is generally a greater preference for instant coffee, whereas in the US there is a greater preference for ground coffee,” Dr Thorpe said.
“And then there’s the frappuccino — the American trend of drinking coffee with lots of sweet additions,” Dr. Sanchez-Roige added.
“There are other caffeinated drinks, and particularly in the context of the UK Biobank, tea, none of which were included in the GWAS, which looked only at coffee,” Dr Palmer said.
“The GWAS study shows that the relationship between genotype and phenotype is more different than the relationship between coffee and tea.”
“Genetics influences many things. For example, it influences how high you can be.”
“And that kind of thing would probably play out very similarly whether you live in the U.S. or the U.K. But coffee is a decision that people make.”
“Coffee comes in a variety of forms, from instant to Frappuccino, and is consumed within cultural norms that vary from place to place,” Dr. Sanchez-Roige said.
“A person with a given genotype may have a completely different phenotype living in the UK than in the US.”
“And that’s what the data tells us. Because unlike height, where your behavior has little to do with it, your behavior and the choices you make in your environment depend on various factors. So the interaction between genotype and environment complicates the picture.”
Teams paper was published in the magazine Neuropsychopharmacology.
_____
