Association of Type 2 Diabetes Mellitus With Dietary Vitamin B12 Intake in Individuals With Different Fat Mass and Obesity‐Associated ( FTO ) Genotypes

Type 2 diabetes mellitus (T2DM) is a multifactorial disease influenced by genetic and environmental factors. The fat mass and obesity‐associated (FTO) gene has been implicated in obesity and metabolic disorders, while vitamin B12 plays a role in glucose metabolism and insulin sensitivity. This study aimed to assess the interaction between dietary vitamin B12 intake and FTO genotypes in relation to T2DM risk. A case–control study was conducted on 400 participants (179 with T2DM and 174 controls) aged 35–70 years. Dietary intake was assessed using a validated food frequency questionnaire, and genotyping of the FTO rs9939609 polymorphism was performed using the tetra‐primer amplification refractory mutation system polymerase chain reaction (Tetra‐ARMS PCR). Logistic regression models were applied to evaluate the association between dietary vitamin B12 intake and T2DM risk, stratified by FTO genotype (TT versus AA/AT). Vitamin B12 intake was significantly higher in participants with the TT genotype of the FTO gene in the control group compared to participants with the TT genotype in the case group (5.44 ± 2.37 vs. 4.03 ± 2.13 μg/day, p = 0.004). Vitamin B12 showed a significant inverse association with T2DM (OR = 0.778, 95% CI 0.636–0.952) in the TT group, whereas no significant associations were observed for the AA/AT group. Higher dietary vitamin B12 intake associated with lower odds of T2DM in individuals with the TT genotype of the FTO rs9939609 polymorphism, suggesting a gene–nutrient interaction that may inform precision nutrition strategies for diabetes prevention.