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.