The Immunomodulatory Role of Vitamin D in Obesity

Background Obesity is fundamentally characterized by low-grade chronic inflammation (LGCI), driven by hypertrophic adipocytes and macrophage infiltration that release pro-inflammatory cytokines (e.g., TNF-α, IL-6). Vitamin D, recognized as a potent immunomodulator, holds significant potential in mitigating this inflammatory cascade. This review evaluates the impact of vitamin D supplementation on the pro-inflammatory cytokine profile and metabolic parameters in patients with obesity and metabolic syndrome. Methods A comprehensive literature review was conducted using PubMed and Google Scholar databases. The analysis encompassed 31 scientific articles, including recent meta-analyses and randomized controlled trials (RCTs), focusing on the interplay between vitamin D, systemic inflammation, and obesity-related metabolic disturbances. Results Current evidence indicates that vitamin D supplementation significantly reduces systemic inflammatory markers (IL-6, hs-CRP, TNF-α) and improves insulin resistance indices (HOMA-IR) and lipid profiles. However, supplementation alone does not induce significant reductions in body mass index (BMI) or total adipose tissue volume. Furthermore, owing to vitamin D sequestration in adipose tissue and volumetric dilution, patients with obesity require personalized, high-dose regimens (often ≥4,000 IU/day) to achieve optimal serum 25(OH)D levels (30–50 ng/mL) necessary for clinical immunomodulation. Conclusions While vitamin D is not a standalone weight-loss intervention, it serves as a crucial adjunctive therapy for modulating the LGCI associated with obesity. Current data do not support extrapolating these anti-inflammatory effects to a definitive reduction in cardiometabolic risk. However, achieving optimal serum levels requires personalized dosing to address altered pharmacokinetics, alongside essential lifestyle modifications, including diet and exercise.