This study investigated whether serum zinc concentration is associated with glucose tolerance, insulin resistance and metabolic health status in Korean adults.

Subjects with available serum zinc levels were recruited from the fifth Korea National Health and Nutrition Examination Survey (KNHANESV) cohort. Those in the highest quartile on homoeostasis model assessment for insulin resistance (HOMA-IR) and with a body mass index (BMI) of 18.5–25kg/m² were classified as metabolically obese and normal weight (MONW).

A total of 1813 subjects with a mean age of 45.2±0.5 years and a mean BMI of 24.01±0.11kg/m² were enrolled. Those in the lower serum zinc quartiles exhibited higher levels of fasting blood glucose and insulin resistance indices compared with those in the higher quartiles. However, these associations were positive only in normal-weight subjects. Those categorized as MONW exhibited significantly lower serum zinc levels than the metabolically healthy and normal weight (MHNW) subjects (131.6±3.0μg/dL vs 141.7±2.8μg/dL, respectively; P=0.0026), whereas serum zinc levels did not differ according to metabolic health in obese subjects. The odds ratio for being categorized as MONW was 4.12 (95% CI: 1.75, 9.72) among those in the lowest serum zinc quartile compared with those in the highest quartile even after adjusting for possible confounding factors.

Lower serum zinc levels were associated with unhealthy metabolic status in normal-weight adults. Further prospective studies are required to define the role of zinc in metabolic health.