Effect of iodine nutrition on blood glucose and blood lipid levels in different regions: Based on quantile regression

Abstract

Objective Iodine is essential for the synthesis of thyroid hormones in the human body, and both excessive and insufficient iodine intake can significantly impact metabolic processes and contribute to various diseases. This study aims to investigate the effects of serum iodine levels and other associated factors on blood glucose and blood lipid levels. Methods A total of 1344 participants were recruited from three distinct regions in Shandong province, each characterized by varying levels of environmental iodine content. Blood and urine samples were collected from each participant and analyzed for iodine nutrition status, blood glucose (BG), blood lipids, and other relevant biochemical indicators. Quantile regression analysis was employed to examine the continuous effects of serum iodine concentration (SIC) and other related factors on BG, total cholesterol (TC), triglycerides (TG), high-density lipoprotein (HDL), and low-density lipoprotein (LDL). Results In men ≥ 45 years, higher SIC was significantly associated with reduced TG at the 75th (β = −0.015, 95%CI: −0.030, 0.000) and 90th (β = −0.035, 95%CI: −0.064, −0.006) percentiles ( P  < 0.05). In men < 45 years, SIC affected TC at the 25th percentile (β = 0.008, 95%CI: 0.001, 0.015; P  < 0.05). In women ≥45 years, SIC increased BG at the 90th percentile (β = 0.006, 95%CI: 0.001, 0.011), TC at the 50th (β = 0.005, 95%CI: 0.002, 0.009) and 75th (β = 0.005, 95%CI: 0.001, 0.009) percentiles, TG at the 50th percentile (β = 0.004, 95%CI: 0.001, 0.007), and HDL-C at the 25th percentile (β = 0.001, 95%CI: 0.000, 0.001) (all P  < 0.05), but had no significant effect on LDL-C. In women <45 years, SIC only increased HDL-C at the 75th (β = 0.005, 95%CI: 0.001, 0.009) and 90th (β = 0.005, 95%CI: 0.001, 0.009) percentiles ( P  < 0.05). Conclusion SIC exerts gender- and age-specific effects on BG and lipids, particularly at upper percentiles of metabolic indicators in adults ≥45 years. These findings highlight the need for targeted iodine nutrition interventions to mitigate metabolic risks.