A study from researchers at McGill University in Montreal suggests that a person's preference for black coffee may be determined by their genetics, but not in the way one might expect. Published in The Journal of Nutrition, the research links the enjoyment of coffee's bitterness to genes that regulate caffeine metabolism, rather than those that control taste perception on the tongue.
By analyzing the DNA of over 125,000 individuals, the scientific team identified 46 genetic variants associated with preferences for 11 different bitter foods. When it came to unsweetened coffee, the data pointed to two specific variants located near the CYP1A1 and CYP1A2 genes. These genes are well-known for their role in instructing liver enzymes to break down caffeine. The findings were validated by cross-referencing them with the self-reported daily coffee consumption of a separate group of more than 9,000 adults, confirming a direct link between the genetic markers and real-world habits.
This discovery distinguishes coffee from other bitter items, such as grapefruit, where preference is more directly tied to genes that manage taste receptors. For coffee, the preference appears to be driven by the post-ingestive reinforcing effects of caffeine. In other words, individuals who metabolize caffeine in a certain way may learn to associate the bitter flavor with the positive physiological effects that follow. While genetics provide a biological nudge, the researchers emphasize that the effect of any single gene is small and that cultural norms and personal habits remain the primary drivers of dietary choices.