Dietary copper and selenium are associated with insulin resistance in overweight and obese Malaysian adults

Imbalance in or inadequate intake of micronutrients may impair insulin synthesis, secretion, and it's signaling pathways. This study aimed to investigate the associations between dietary copper (Cu) and selenium (Se) with insulin resistance (IR), in overweight/obese adults. We hypothesized that dietary Cu and Se are associated with IR in a non-linear trend. A cross-sectional study was conducted on 128 non-diabetic overweight and obese Malaysian adults aged ≥18 years with a body mass index ≥23 kg/m2. Dietary intake was assessed using food frequency questionnaire. IR was defined as homeostatic model assessment-insulin resistance (HOMA-IR) ≥1.7. Locally weighted scatterplot smoothing regression was performed to detect non-linearity and piecewise regression models were computed to examine the trend of the associations at different cut off points. In this study, 45% (n = 57) of the study participants were found to be insulin resistant. A U-shaped non-linear relation between Se and HOMA-IR was observed. Three-piecewise regression models revealed positive association between Se and HOMA-IR in individuals with relatively low (<0.3 µg/kg/d) and high (≥1.01 µg/kg/d) intake of Se (β coefficient = 3.835, CI = -12.216 to 19.886, P= 0.614; and β coefficient = 0.785, CI = 0.386-1.185, P = 0.014, respectively). Significant positive association was only found between dietary Cu and HOMA-IR with intake of Cu ≥ 13.4 µg/kg/d, 0.276 (CI = 0.025-0.526; P = 0.033). In conclusion, our findings reveal that a critical balance in the dietary intake of copper and Se is crucial for health, more so in insulin resistant and diabetic individuals. In the latter treatment should include measured intake of both copper and Se, personalized according to individual habitual food preferences and intakes.