Summary: Individual differences in coffee consumption appear to be partly genetic. New analysis estimates that 36% to 58% of how much coffee people drink is heritable and suggests a positive feedback loop between genes and environment—what researchers call quantile-specific heritability.
Source: DOE/Lawrence Berkeley National Laboratory
Why do some people need three cups of coffee to get through the day while others are satisfied with one or none at all? Recent research argues that both genes and environment interact in a way that amplifies differences in coffee consumption. That interaction helps explain why coffee drinking varies so much between individuals and why family patterns are so consistent for heavy drinkers.
Researchers describe this pattern using the concept of quantile-specific heritability. In plain terms, genetic effects on a trait like coffee intake are not uniform across the population; instead, genetic influence becomes stronger among heavier drinkers. The same statistical pattern has been observed for other traits such as cholesterol levels and body weight, suggesting broader implications for how we understand gene–environment interplay in human behavior and physiology.
“It appears that environmental factors set the stage for genetic influences to emerge,” said Paul Williams, a statistician at Lawrence Berkeley National Laboratory. “If your social circle, workplace, or neighborhood encourages more coffee drinking, the genes that predispose you to enjoy or tolerate more caffeine will have a larger effect. Those environmental and genetic influences act together.”
Williams’ analysis, published in the journal Behavioral Genetics, used detailed family data from the Framingham Study — a long-running cardiovascular cohort started in 1948. He analyzed 4,788 child–parent pairs and 2,380 sibling pairs, taking advantage of the study’s repeated, detailed measures of diet, lifestyle, medications, and medical history collected every three to five years. Because the Framingham dataset follows multiple generations from the same families, it is well suited to separate inherited influences from environmental ones.
Using quantile regression, Williams measured how parent-offspring and sibling concordance in coffee intake varies across the distribution of consumption. Traditional heritability estimates assume that inherited effects are constant for everyone, but quantile regression lets researchers see whether that influence changes among light, moderate, or heavy drinkers.
The results showed that estimated heritability of coffee intake ranged from about 36% to 58%, but the key finding was that parent–offspring and sibling similarity increased across higher consumption quantiles. In other words, the relationship between a parent’s and an offspring’s coffee intake was weakest among light drinkers and strongest among heavy drinkers. The study reported progressively larger offspring intake associated with each additional cup/day in parents as offspring moved from low to high consumption quantiles, consistent with quantile-specific heritability.
Previous research has identified major environmental contributors to coffee consumption, including cultural and geographic factors, age, sex, and tobacco smoking. The new findings help clarify why heritability estimates differ across subgroups: if males, smokers, or people in certain regions tend to drink more, then the estimated genetic contribution will be larger in those higher-consuming groups. That interaction can produce the appearance of gene–environment interaction even when genes and environment act synergistically.
“When the human genome was first decoded many expected a straightforward mapping from genes to behavior,” Williams noted. “But for many complex traits we see that genes explain only a fraction of variation when considered alone. Quantile-specific analyses show how environmental context shapes when and where genetic influences become important.”
Paul Adams, director of the Laboratory’s Molecular Biophysics & Integrated Bioimaging (MBIB) Division, observed that these statistical insights complement laboratory genomics research, helping to clarify how genes and environment combine to shape behaviors like coffee drinking.
Williams plans to extend this quantile-specific approach to other traits, including alcohol consumption and measures of pulmonary function. He and his colleagues believe this line of work opens a new avenue for understanding when genetic effects are most influential and how environmental exposures amplify or dampen those effects. Ultimately, quantile-specific heritability may change how researchers interpret genetic contributions to complex human traits.
Funding: This research received support from a grant by the National Institute of Environmental Health Sciences and a gift from HOKA ONE ONE. Framingham Study data were provided through the Biologic Specimen and Data Repository Information Coordinating Center of the National Heart, Lung, and Blood Institute.
Source:
DOE/Lawrence Berkeley National Laboratory
Media Contacts:
Aliyah Kovner – DOE/Lawrence Berkeley National Laboratory
Image Source:
The image is in the public domain.
Original Research: Closed access — “Quantile-Specific Heritability may Account for Gene–Environment Interactions Involving Coffee Consumption,” Paul T. Williams. Behavioral Genetics. DOI: 10.1007/s10519-019-09989-0.
Abstract (summary)
Heritability estimates for coffee intake vary from roughly 0.36 to 0.58. Those point estimates assume inherited effects are equal across the intake distribution. Quantile regression of 4,788 child–parent pairs and 2,380 siblings found that parent–offspring and sibling concordance increased with higher quantiles of coffee intake. Small or non-significant offspring responses to parental intake were observed at low consumption quantiles, while progressively larger associations appeared at median and upper quantiles. This pattern suggests that factors distinguishing heavier from lighter drinkers (for example, smoking or male sex) influence measured heritability, producing quantile-specific effects.