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

## TL;DR

This study shows how iodine levels in the blood affect blood sugar and cholesterol differently in men and women, especially in older adults.

## Contribution

The study reveals gender- and age-specific effects of serum iodine on metabolic indicators using quantile regression.

## Key findings

- Higher serum iodine levels in older men significantly reduced triglycerides at upper percentiles.
- In older women, higher iodine levels increased blood glucose and cholesterol at specific percentiles.
- Iodine's effects on metabolic markers vary by gender and age, particularly in adults over 45.

## Abstract

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.

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).

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).

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.