Statistics used to find how genetics influence coffee intake

Some people feel the need to drink three cups of coffee in a day while others feel content with just one cup, and others give up coffee entirely. Why is this?

Image Credit: Marina Keremkhanova/Shutterstock

A new study indicates that the consumption of coffee—the most consumed beverage in the United States, apart from tea, bottled water, beer, and sodas—is influenced by a positive feedback loop between genetics and the environment.

Termed “quantile-specific heritability,” the phenomenon is related to cholesterol levels and body weight and considered to govern human physiological and behavioral attributes that defy basic explanation.

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 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.”

Paul Williams, Statistician, Lawrence Berkeley National Laboratory

The outcomes of the study by Williams, reported in the Behavioral Genetics journal, were derived from an analysis of 4,788 child–parent pairs and 2,380 siblings from the Framingham study—a well-known, ongoing study implemented by the National Institutes of Health in 1948 to analyze how lifestyle and genetics influence the rates of cardiovascular disease.

Participants, all related to an original group from Framingham, Massachusetts, presented detailed information about diet, medication use, exercise, and medical history for every three to five years. The study data have been utilized in thousands of analyses into several aspects of human health.

A dose of statistics

A statistical method known as quantile regression was used by Williams to predict what proportion of participants’ coffee drinking could be influenced by genetics—as the investigation follows families—and what must be affected by external factors.

Paul T. Williams. Image Credit: Roy Kaldschmidt/Berkeley Lab.

Previous studies reveal that the most important environmental factors that influence coffee drinking are culture, age, sex, geographical location, and whether one smokes tobacco. In general, older male smokers of European origin were found to drink the most.

The study reported that 36% to 58% of coffee consumption is genetically influenced (although the exact genes responsible are still unknown).

However, Williams’ postulate that coffee consumption is a quantile-specific trait was confirmed by the increasingly stronger correlation between coffee consumption of a parent and that of an offspring for each offspring’s coffee-drinking quantile, or bracket (for instance, zero cups per day, one to two cups, 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.”

Paul Williams, Statistician, Lawrence Berkeley National Laboratory

Williams, who is also a staff scientist in Berkeley Lab’s Molecular Biophysics & Integrated Bioimaging (MBIB) Division, 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.”

The conventional hypothesis in genetic studies has been that a person’s lifestyle and surroundings modify gene expression levels in quantifiable and consistent ways, eventually developing the outward manifestation—known as a phenotype—of a trait. The statistical study by Williams demonstrates that the situation is highly complex, which helps elucidate the diversity of attributes observed in the real world.

Paul’s statistical studies complement the genomics research that Berkeley Lab bioscientists conduct to learn more about the relationship between genes and the environment.”

Paul Adams, Director, Molecular Biophysics & Integrated Bioimaging Division, Lawrence Berkeley National Laboratory

As a next step, Williams intends to evaluate whether quantile-specific heritability influences pulmonary function and alcohol consumption. “This is a whole new area of exploration that is just now opening up,” he said. “I think it will change, in a very fundamental way, how we think genes influence a person’s traits.”

This study was financially supported by a grant from the National Institute of Environmental Health Sciences and a bestowal from HOKA ONE ONE. The Framingham Study Data were obtained through the Biologic Specimen and Data Repository Information Coordinating Center of the National Heart, Lung, and Blood Institute.