Why do we drink coffee? Maybe it's your genes, or your friends

If we are surrounded by colleagues and friends who drink coffee, we are more likely to drink it too. — AFP

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, 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 of 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% and 58% 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 child’s coffee consumption percentile.

“When we started to decode the human genome, we thought we’d be able to read the DNA and understand how genes translate into behaviour, medical conditions and such. But that’s not the way it’s worked out.

"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,” he says.

“It appears that environmental factors sort of set the groundwork in which your genes start to have an effect.

“So, if your surroundings predispose you to drinking more coffee – like your co-workers 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,” he explains.

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 the United States, with a cup of joe coming in above bottled water, soft drinks, tea and beer. – AFP Relaxnews