Vitamin D Levels and Their Relationship with Lipid Metabolism and Inflammatory Markers in Healthy Adults

Objective: This study investigates the associations between serum vitamin D levels and biochemical, hematological, and inflammatory markers in a healthy adult population, focusing on their implications for lipid metabolism and systemic inflammation. Methods: A retrospective analysis was conducted on the medical records of 267 individuals aged 18–65 years, who presented to the internal medicine outpatient clinic with complaints of fatigue. Inclusion criteria ensured the absence of comorbid diseases or active conditions. Serum vitamin D levels were categorized into three groups: deficient-insufficient (≤19 ng/mL), sufficient (20–29 ng/mL), and normal (≥30 ng/mL). Biochemical parameters, hematological markers, and derived ratios (e.g., triglyceride/glucose ratio, monocyte/HDL-C ratio) were analyzed. Spearman correlation, Kruskal-Wallis H test, and Mann-Whitney U test were used for statistical analysis. Results: Vitamin D levels showed significant positive correlations with HDL-C (ρ = 0.169, p = 0.0055) and LDL-C (ρ = 0.198, p = 0.0011), and a negative correlation with neutrophil counts (ρ = -0.133, p = 0.030). Among derived ratios, the triglyceride/monocyte ratio exhibited a significant positive correlation (ρ = 0.160, p = 0.0088), while the monocyte/HDL-C ratio showed a significant negative correlation (ρ = -0.203, p = 0.00083). Group comparisons revealed significantly lower HDL-C levels in the deficient-insufficient group compared to the sufficient and normal groups (p = 0.0022). No significant differences were found for other lipid or inflammatory markers. Conclusion: This study highlights the multifaceted roles of vitamin D in lipid metabolism and systemic inflammation. The positive association with HDL-C underscores its potential cardioprotective effects, while the negative correlation with neutrophil counts suggests its role in modulating inflammation. These findings provide valuable insights into vitamin D’s broader physiological effects in healthy individuals, warranting further large-scale studies.