Summary: New research suggests a preference for black coffee and dark chocolate may stem from genetic differences in how people metabolize caffeine. People with genetic variants tied to faster caffeine metabolism tend to choose bitter, unsweetened coffee and are also more likely to favor dark chocolate.
Source: Northwestern University
People who prefer their coffee black are also more likely to prefer dark chocolate, according to a study from Northwestern Medicine. The researchers say the link can be traced to genes that influence caffeine metabolism.
The study found that individuals carrying genetic variants associated with faster caffeine metabolism tend to choose bitter, black coffee rather than coffee with milk and sugar. Those same genetic markers were more common among people who prefer dark chocolate to milk chocolate.
Rather than a pure taste-driven preference, the researchers propose that this pattern reflects a learned association: people who experience a stronger or more noticeable stimulant effect from caffeine may come to associate that psycho-stimulant effect with bitterness. Over time, that association leads them to favor bitter foods and beverages that signal the presence of caffeine.
“These gene variants affect how quickly the body clears caffeine, not the sense of taste itself,” said lead author Marilyn Cornelis, associate professor of preventive medicine in nutrition. “Because these individuals metabolize caffeine more rapidly, its stimulating effects dissipate sooner and they tend to consume more to maintain the effect. They appear to learn to link bitterness with that caffeine-driven alertness.”
Cornelis and colleagues interpret the findings as evidence of a conditioned preference: when people expect the cognitive boost of caffeine, they associate that effect with bitter flavors and therefore gravitate to black coffee and similarly bitter items such as dark chocolate.
The study was published Dec. 13 in Scientific Reports.
Dark chocolate’s connection to caffeine preference may reflect its content of caffeine-related stimulants. Though dark chocolate contains only a small amount of caffeine, it is richer in theobromine, a related compound with mild stimulant properties. This may reinforce the association between bitter flavor and stimulant effects for some consumers.
Why this matters
Both coffee and dark chocolate have been linked, in observational studies, with lower risks of certain diseases. Moderate coffee intake has been associated with reduced risk of Parkinson’s disease, some cardiovascular conditions, type 2 diabetes and several cancers, while dark chocolate has been associated with heart health benefits. Those findings come from epidemiological research, which establishes associations but cannot prove causation.
Cornelis’s work suggests genetic variants tied to caffeine metabolism can serve as more precise instruments when studying how coffee consumption affects health. Prior genetic studies often treated “coffee drinkers” as a single group without distinguishing how people prepare or flavor their coffee. These new results indicate that genetic markers linked to caffeine metabolism are stronger indicators of a preference for black coffee specifically, which may influence the interpretation of genetic studies that aim to assess coffee’s health effects.
“Choosing black coffee versus coffee with cream and sugar represents more than a taste preference—it reflects different consumption patterns and likely different overall exposures,” Cornelis said. “By distinguishing types of coffee drinkers, we can refine how genetic data are used to evaluate health outcomes related to coffee and other bitter foods.”
The study emphasizes moderate consumption—roughly two to three cups of coffee a day—as the context for potential benefits identified in observational research.
Researchers based their analysis on genetic information, dietary records and self-reported food preferences from the UK Biobank and two U.S. cohorts: the Nurses’ Health Study and the Health Professionals Follow-up Study.
The paper is titled “Genetic determinants of liking and intake of coffee and other bitter foods and beverages.”
About this genetics research news
Author: Marla Paul
Source: Northwestern University
Contact: Marla Paul – Northwestern University
Image: The image is in the public domain
Original Research: Open access.
“Genetic determinants of liking and intake of coffee and other bitter foods and beverages” by Marilyn C. Cornelis et al., Scientific Reports
Abstract
Genetic determinants of liking and intake of coffee and other bitter foods and beverages
Coffee is a widely consumed beverage that is naturally bitter and contains caffeine. Genome-wide association studies (GWAS) of coffee drinking have identified genetic variants involved in caffeine-related pathways but not in taste perception.
Because many people alter coffee’s taste by adding milk or sweeteners, previous GWAS that treated coffee drinking as a single behavior may have missed important distinctions. Using UK and U.S. cohorts, the authors tested whether genetic variants related to taste are more strongly associated with consumption of black coffee than with coffee consumed with milk or sweeteners, and whether variants tied to caffeine pathways differ according to coffee type independent of caffeine content.
Contrary to the initial hypotheses, the study found that genetically inferred caffeine sensitivity was more closely linked to coffee taste preferences than were genetic indicators of bitter taste perception. Similar patterns were observed for tea and dark chocolate.
Overall, the findings suggest that taste preferences and physiological responses to caffeine are intertwined in ways that can reflect conditioned preferences, making it challenging to separate sensory taste from learned associations with stimulant effects.