rs1031391 (TAS2R14): Caffeine and Quinine Bitterness

Key takeaways

• rs1031391 lies in the chromosome 12 bitter taste receptor cluster (the 10.88-11.24 Mb region containing TAS2R14, PRR4, and PRH1), one of two major genomic hubs of human bitter taste receptor genes.
• Genetic variants in this cluster explain roughly 8.9% of individual variation in how bitter caffeine tastes, based on a genome-wide association study in a Brazilian population.
• The same cluster explains about 23.2% of variation in quinine bitterness sensitivity, with the effect concentrated at low quinine concentrations and absent at high concentrations.
• The caffeine-associated and quinine-associated signals in this region are statistically independent of each other, suggesting multiple distinct functional variants at this locus.
• Evidence comes from a combined cohort of about 600 individuals from Sao Paulo, Brazil, which limits statistical power and generalizability to other populations.

What the research says A genome-wide association study (a large-scale genetic scan that identifies statistical links between DNA variants and traits) of bitter taste perception in a Brazilian population with mixed European, African, and Asian ancestry (504 discovery participants, 104 validation participants) identified the chromosome 12 bitter taste receptor cluster, a region containing TAS2R14 (a bitter taste receptor gene), PRR4, and PRH1, as significantly associated with both caffeine and quinine bitterness perception. The cluster's lead variant for caffeine bitterness (rs2708377) explained 8.9% of the variation between individuals in how bitter they rated caffeine (beta = -0.12, a standardized effect size), while a distinct variant (rs10772420) in the same region explained 23.2% of individual variation in quinine perception (beta = 0.25) at replication. The quinine effect was concentration-specific: strong at low quinine concentrations, undetectable at high concentrations, suggesting that variation at this locus shifts sensory threshold rather than maximum perceived intensity.

Reported associations

• Caffeine bitterness perception: Variation at this locus is associated with how intensely caffeine is perceived as bitter; the cluster's lead variant explained 8.9% of variation between individuals (beta = -0.12) in a discovery cohort of 504 people from Brazil.
• Quinine bitterness perception at low concentration: Variation at this locus is associated with quinine bitterness sensitivity specifically at low doses, explaining 23.2% of individual variation (beta = 0.25), replicated in a second cohort of 104 people.
• Quinine bitterness perception at high concentration: No statistically significant association was detected between this locus and quinine bitterness at high concentrations, indicating the genetic effect is threshold-specific rather than ceiling-specific.

Evidence quality The source study used a discovery panel of 504 and a validation panel of 104 individuals from the general population of Sao Paulo, Brazil, a population characterized by continuous European, African, and Asian genetic admixture. These sample sizes are modest by current genome-wide association standards, limiting statistical power for small effects and applicability to non-Brazilian populations. The caffeine association achieved genome-wide significance (P = 5.31 x 10^-13) and the quinine association was replicated with high statistical confidence (P = 4.97 x 10^-37). The study explicitly establishes two statistically distinct signals within this cluster, one for caffeine (rs2708377) and one for quinine (rs10772420), demonstrating complex genetic architecture at this locus. No conflicting findings are reported within the study. Phenotyping was notably detailed: both detection thresholds and above-threshold intensity ratings were measured across five concentration levels per compound, which adds confidence to the concentration-specific quinine finding but also means the small sample carried a heavy measurement burden that could affect statistical reliability.

Lifestyle considerations

• Caffeine (nutrition, mixed, low): Variants in the TAS2R14 locus region are linked to differences in how bitter caffeine is perceived, which may relate to individual variation in preferences for caffeinated beverages.
• Quinine (nutrition, mixed, low): Variation at this locus is linked to low-concentration quinine bitterness sensitivity, which may be relevant to individual tolerance of quinine-containing drinks such as tonic water.