BMI as a Mediator in the Relationship Between Dietary Trace Elements and Type 2 Diabetes Mellitus: Findings from a Rural Cohort

Objectives: This study aims to examine the relationship between dietary trace elements and Type 2 diabetes mellitus (T2DM), as well as to assess the influence of body mass index (BMI) on this relationship. Methods: A total of 38,384 participants participated in this study. Dietary intakes of iron, copper, zinc, heme iron, and non-heme iron were assessed using validated food frequency questionnaires. The odds ratio (OR) and 95% confidence interval (CI) were calculated using the logistic regression model to evaluate the association of dietary intake of iron, copper, zinc, heme iron, and non-heme iron with T2DM. Restrictive cubic splines (RCS) were used to explore the dose–response relationship. In addition, causal mediation analysis was used to explore the role of BMI. Results: After adjusting for the relevant covariates, the highest quartile (Q4) compared with the lowest quartile (Q1) the odds ratios and 95% confidence intervals of iron, heme iron, non-heme iron, copper, and zinc between T2DM were 0.81 (0.70–0.92), 0.81 (0.70–0.92), 0.79 (0.70–0.90), 0.64 (0.77–0.72), and 0.65 (0.55–0.78), respectively. The RCS results showed that the hazards of copper and heme iron in T2DM decreased with the increase in dose (p-non < 0.05). The results of the mediation analysis showed that BMI mediated the association between dietary trace elements and T2DM. Furthermore, subgroup analysis showed the same results. Conclusions: This study indicates that moderate intake of dietary trace elements may help reduce the incidence of T2DM in rural areas. BMI can mediate the association between the two.