Inverse association of triglyceride-glucose and triglyceride/HDL-c indexes with serum 25(OH) vitamin D levels in US adults.

The triglyceride-glucose index (TyG) and the triglyceride to high-density lipoprotein ratio (TG/HDL-c) are novel indicators for assessing insulin resistance (IR) in epidemiological studies. This study aimed to evaluate the association between 25-hydroxy-vitamin D [25(OH)D] levels and these two indicators in the adult population of the United States. 14,380 participants aged 20 years and older were included from the National Health and Nutrition Examination Survey (NHANES). Multivariable linear regression models were used to analyze the association between 25(OH)D and TyG, as well as TG/HDL-c. Smooth fitting curves were employed to identify potential non-linear relationships between 25(OH)D, TyG, and TG/HDL-c. The findings revealed a negative association between 25(OH)D and TyG, with the effect being more pronounced in males and individuals with diabetes (p < 0.01). Similarly, 25(OH)D was negatively associated with TG/HDL-c, with a stronger impact observed in males compared to females. The study population was divided into four quartiles based on 25(OH)D concentration, and TyG and TG/HDL-c levels in Q3 and Q4 were lower than those in Q1. Furthermore, a non-linear relationship was observed between 25(OH)D and TyG, with an inflection point at 19.352 ng/mL. A non-linear relationship was also found between TG/HDL-c and 25(OH)D, with an inflection point at 37.211 ng/mL. 25(OH)D is an independent factor significantly associated with TyG and TG/HDL-c indexes. This negative association may be related to the role of 25(OH)D in insulin resistance.