Why do some people love coffee, like they need it to be fully functional, but others can barely handle a sip let alone finish a full cup of it? New research suggests that it has something to do with their genes and the environment.
Gene-environment interactions involving coffee consumption
Paul T. Williams, a statistician from the Molecular Biophysics & Integrated Bioimaging Division of the Lawrence Berkeley National Laboratory, explained in a study that the gene-environment interactions involving consumption are a phenomenon called “quantile-specific heritability.” It is the same phenomenon that is also linked with body weight and cholesterol and is believed to be involved in other behavioral and physiological traits of humans. The quantile-specific heritability suggests that factors that distinguish lighter vs. heavier coffee drinkers will likely manifest in an estimated heritability.
For instance, a person’s surroundings predispose them to drink more coffee, then the genes they possess likewise influence them to like coffee. Williams refers to these effects as “synergistic.” He added that this can happen to people whose spouse or coworkers drink a lot of coffee or they live in areas with many coffee shops. The “environmental factors sort of set the groundwork in which your genes start to affect,” he continued.
William’s findings, which appeared in the journal Behavioral Genetics, used the popular and ongoing Framingham study launched by the National Institutes of Health in 1948. The study involved 2,380 siblings and 4,788 child-parent pairs, conducted to investigate how genetics and lifestyle affect the rate of people affected by cardiovascular disease. Thousands of investigations have used the data from the Framingham study to know different facets of health. For William’s research, the participants involved were also related to the original Framingham group and they submitted detailed information about their medical history, current medication use, exercise, and diet every three to five years.
The use of the statistical approach
According to Williams, he used the quantile regression, which is a statistical approach, to calculate the proportion of people’s coffee-drinking that could be connected to genetics since the analysis also follows families and the proportion influenced by environmental factors. Previous studies have shown some of the most significant external factors that influence coffee drinking and these include sex, age, geographic location, whether or not a person is also a tobacco smoker, and culture.
Coffee drinking, a quantile-specific trait
The result of William’s statistical study approach showed that about 36 to 58% of coffee intake is determined by genetics. It remains unknown, though, what these exact causative genes are. Based on William’s hypothesis, people’s coffee drinking is considered a quantile-specific trait. This means that the connection between a parent’s coffee consumption and their offspring’s coffee consumption grows stronger for every offspring’s coffee consumption bracket or quantile. Each coffee cup per day increase in the parents’ coffee drinking was correlated with the offspring's coffee intake increase of 0.020 to 0.013 cup per day.
Williams, who is also a staff scientist at the Berkeley Lab, also shared via medical platform Medical Xpress that when they started decoding the human genome in the lab, they thought that they could read the DNA and then understand how genes will translate into medical conditions, behavior, and such. However, that is not the way it worked out. For instance, they’ve known that coffee consumption has a genetic component, such that it runs in the families. Yet, when they started looking at people’s DNA itself, they only found a small percentage of the trait variation that can be connected solely to genes.
When it comes to genetic research, the traditional hypothesis is that a person’s lifestyle and surroundings alter the level of gene expression in measurable and consistent ways, thus creating the phenotype (outward manifestation) of the trait. The statistics provided by William, though, show that the situation can be more complex, explaining traits’ diversity that is manifesting in the real world. Williams said that he is planning to assess whether the quantile-specific heritability also plays a role in pulmonary function and alcohol consumption. He believes that this “new area of exploration” will help change how we think genetics influence a person’s traits.
Caffeine perception and bitter receptor genes
A team of researchers from Osaka University and Riken Center for Integrative Medical Sciences (IMS) have also recently found that it could be in people’s genes why some prefer tea over coffee. They studied the food preferences and genetic data of over 160,000 people in Japan to come up with such findings. The team found nine genetic locations linked with consuming tea, coffee, cheese, yogurt, alcohol, natto (fermented soybeans), meat, vegetables, fish, and tofu. The team also observed the variants responsible for participants’ ability to taste bitter flavors. This is about the 2014 study that was published in the PLOS ONE journal. It shared that people with stronger bitterness perception like coffee more and people with lower bitterness perception liked coffee less.
Countries that drink the most coffee
According to statistics provided by the International Coffee Organization, Finland is most fond of the coffee bean. It consumes about 12 kg per capita or person per year. Whether it be casual coffee in the morning or a regular coffee break, coffee is a highlight of Finnish culture. Coffee drinking has also become a social activity in Finland and coffee is almost always served during a visit to homes, even if people visit unannounced. The trend is also likely because of extremely cold temperatures in the country, dipping minus 40 degrees in Northern Finland.
Top two in the list of countries that drink the most coffee is Norway (9.9 kg per person per year), followed by Iceland (9kg), Denmark (8.7 kg), Netherlands (8.4kg), Sweden (8.2 kg), Switzerland (7.9 kg), Belgium (6.8 kg), Luxembourg (6.5 kg), Canada (6.2 kg), Bosnia and Herzegovina (6.1 kg), Austria (5.9 kg), Italy (5.8 kg), Slovenia (5.8 kg), and Brazil (5.5 kg).
Coffee bean production
Our World in Data, a scientific online publication that focuses on large global problems, also shared the countries that produced the most coffee beans in 2018. This includes Brazil (3.56 million tonnes), Vietnam (1.62 million tonnes), Indonesia (722,461 tonnes), Columbia (720,634 tonnes), and China (100,332 tonnes), Peru (369,622 tonnes), Honduras (481,053 tonnes), Ethiopia (470,221 tonnes), and India (326,982 tonnes), among others.
Coffee research, such as the connection of genetic predisposition, environmental factors, and coffee drinking, is necessary as more and more people are introduced to the addictive drink.