New US research has found that how much coffee we drink is partly due to genetics, and partly influenced by how much coffee our family, friends, and colleagues are drinking. Carried out by Paul Williams, a statistician at Lawrence Berkeley National Laboratory (Berkeley Lab), the new study looked at 4,788 child-parent pairs and 2,380 siblings who were asked to report on their diet, exercise, medication use, and medical history every three to five years as part in the Framingham Study, which investigates how lifestyle and genetics can affect the risk of cardiovascular disease.
Williams used a statistical approach called quantile regression to calculate how much of the participants' coffee drinking could be explained by genetics, and how much is influenced by the external environment. The findings, published in the journal Behavioral Genetics, showed that between 36 percent and 58 percent of the participants' coffee intake was genetically determined.
However, a phenomenon known as ‘quantile-specific heritability’, also appeared to be at work, which is when genetics and the environment influence each other. Williams found that each cup per day increase in the parents' coffee consumption was associated with an increase in coffee intake for each offspring's coffee consumption percentile, for example, per zero cups per day, per one to two cups per day, per two to four cups, and five or more cups.
“When we started to decode the human genome, we thought we'd be able to read the DNA and understand how genes translate into behavior, medical conditions, and such. But that's not the way it's worked out,” said Williams. He added, “For many traits, like coffee drinking, we know that they have a strong genetic component -- we've known coffee drinking runs in families since the 1960s. But, when we actually start looking at the DNA itself, we usually find a very small percentage of the traits' variation can be attributed to genes alone.”
“It appears that environmental factors sort of set the groundwork in which your genes start to have an effect," explains Williams, "So, if your surroundings predispose you to drinking more coffee—like your coworkers or spouse drink a lot, or you live in an area with a lot of cafes—then the genes you possess that predispose you to like coffee will have a bigger impact. These two effects are synergistic.”
Past research has also shown that certain environmental factors can influence how much coffee we drink, notably, culture, geographic location, age, sex, and smoking status, with older male smokers of European ancestry drinking the most coffee, overall. Coffee is the most popular drink in America, with a cup of Joe coming in above bottled water, sodas, tea and beer.