Exploratory Genome-Wide Association Study of Grapefruit Intake and Its Potential Link to Obesity Risk in US Cohorts

Background/Objectives: Understanding the genetic basis of food consumption is a key step toward precision nutrition, viewed as a long-term future perspective. This study aimed to investigate genetic variants associated with grapefruit (Citrus paradisi) intake and to evaluate their potential relationship with obesity risk. Methods: A genome-wide association study (GWAS) was conducted on 19,653 European-ancestry participants from two prospective cohorts, the Nurses' Health Study (NHS) and the Health Professionals Follow-Up Study (HPFS). We employed a functional annotation strategy to select a suggestive locus for follow-up analysis, and computationally derived molecular docking simulations explored a plausible functional link between grapefruit's bioactive compounds and the candidate gene product. Results: Although falling short of the conventional threshold for genome-wide significance, a suggestive locus was prioritized on chromosome 14, with the lead single nucleotide polymorphism (SNP), rs2124 (p < 5 × 10^-6), located within the metabolic gene ADCK1 (aarF domain containing kinase 1). Molecular docking simulations supported a plausible mechanistic hypothesis, indicating that key bioactive compounds in grapefruit could bind with high affinity to the ADCK1 protein. Consistent with the GWAS finding, individuals with the CC genotype reported lower mean grapefruit intake. This genotype was also associated with other lifestyle factors, notably, lower physical activity in women. In age- and multivariate-adjusted models, the CC genotype was associated with a modestly increased risk of incident obesity in females, but not in males. Conclusions: Our exploratory findings suggest a prioritized candidate locus associated with grapefruit intake, and its link to obesity risk may be mediated by the metabolic gene ADCK1. However, given the lack of genome-wide significance and independent replication, these findings should be considered preliminary and exploratory. These hypothesis-generating results support the integration of genetics and dietary habits, warranting further mechanistic validation.