Nutrigenomics of Type 2 Diabetes Risk: Investigating Gene-Diet Interactions in Adult Populations Across Diverse Nigerian Ethnic Groups

Nutrigenomics investigates the interaction between individual genetic variants and dietary exposures in determining metabolic phenotypes and disease risk. Type 2 diabetes mellitus is among the most rapidly increasing non-communicable diseases in Nigeria, yet gene-diet interaction research in Nigerian populations is critically limited, constraining the development of precision nutrition strategies appropriate for this genetic and dietary context. This thesis investigates gene-diet interactions relevant to type 2 diabetes risk across ethnically diverse adult populations from three major Nigerian ethnic groups (Yoruba, Igbo, and Hausa-Fulani) in a cross-sectional candidate gene study supplemented by polygenic risk score analysis. A study sample of 720 adults comprising 240 individuals from each ethnic group (120 with type 2 diabetes, 120 controls) was recruited across Ibadan, Enugu, and Kano. Dietary assessment used a validated ethnic-specific food frequency questionnaire developed in prior research. Genetic analysis targeted 48 single nucleotide polymorphisms in genes regulating carbohydrate metabolism, lipid metabolism, adipokine signalling, and inflammation previously associated with type 2 diabetes risk, supplemented by polygenic risk score computation. Gene-diet interaction analyses used multivariable logistic regression with interaction terms and were corrected for multiple testing. Results identified significant interactions between traditional high-fibre food consumption patterns and the TCF7L2 rs7903146 variant, with the protective effect of high dietary fibre being significantly greater in T-allele carriers. Ethnic group moderated several gene-diet interaction effects, highlighting the importance of population-specific analyses. Keywords: nutrigenomics, gene-diet interaction, type 2 diabetes, ethnic groups, Nigeria.