Differential Associations of Vitamin D Metabolites with Adiposity and Muscle-Related Phenotypes in Korean Adults: Results from KNHANES 2022-2023.

BACKGROUND

Body composition plays a crucial role in metabolic health, aging, and the development of various diseases. Vitamin D has been implicated in the regulation of muscle and adipose tissue function, but its relationship with body composition remains unclear.

OBJECTIVES

This study aimed to investigate the association between serum 25-hydroxyvitamin D (25[OH]D) concentration, its subspecies, and body composition parameters and related phenotypes in Korean adults aged ≥20 years.

METHODS

This cross-sectional study included 2612 eligible participants from the Korea National Health and Nutrition Examination Survey 2022-2023, and data on body composition parameters and serum 25(OH)D levels were analyzed. Serum 25(OH)D levels and subspecies were determined using liquid chromatography-tandem mass spectrometry. Body composition factors included anthropometric indices, muscle strength, and fat and muscle mass, which were assessed using bioelectrical impedance analysis.

RESULTS

After multivariable adjustment, serum concentrations of total 25(OH)D and 25(OH)D3 were inversely associated with waist circumference, body mass index, and fat mass and positively associated with handgrip strength and lean mass, whereas serum 25(OH)D2 and 3-epi-25(OH)D3 levels showed no such associations. Higher 25(OH)D2 concentrations were positively associated with low muscle strength and the prevalence of sarcopenia. Through non-linear analyses, U-shaped correlations were identified between total 25(OH)D and 25(OH)D3 levels with low muscle mass, respectively, while a J-shaped correlation was observed between 25(OH)D2 level and low muscle mass.

CONCLUSIONS

Total 25(OH)D and 25(OH)D3 levels were inversely associated with adiposity and positively associated with muscle strength and lean mass, whereas the 25(OH)D2 level was linked to low muscle strength and sarcopenia. The U- and J-shaped associations with low muscle mass indicate the complex and differential roles of vitamin D subspecies, warranting further study.