Vitamin D status in patients with oral leukoplakia and oral squamous cell carcinoma: a systematic review and meta-analysis

Vitamin D deficiency has been widely evidenced to be associated with promoting cancer progression. Herein, we performed a meta-analysis and systematic review of studies assessing vitamin D status in oral leukoplakia (OLK) and oral squamous cell carcinoma (OSCC). This review was registered in PROSPERO (CRD420251113481) and followed PRISMA guidelines. We searched PubMed, Embase, Scopus, and Web of Science, with manual searches of reference lists through August 2025. Meta-analyses of proportion deficiency were performed using random-effects models. A total of seven studies met inclusion criteria, involving a total of 317 healthy controls, 45 OLK patients, and 168 OSCC patients. Vitamin D deficiency rates were 45% (threshold: 30 ng/mL) and 65% (35 ng/mL) in healthy controls, exceeding 90% in OLK/OSCC patients at both thresholds. Compared with healthy controls, a significant difference was observed in the forest plot in OLK patients (odds ratio (OR) = 36.84, 95% CI: 7.35–184.51, I2 = 0%), and in OSCC patients (OR = 32.43, 95% CI: 4.40–238.96, I2 = 35.5% at 30 ng/mL; OR = 4.67, 95% CI: 2.31–9.45, I2 = 0% at 35 ng/mL). Serum vitamin D concentrations were consistently lower in OSCC patients than healthy controls (pooled weighted mean differences: -15.35 ng/mL, 95% CI: -19.33 ng/mL to -11.36 ng/mL, I2 = 66.4% ). This systematic literature review and meta-analysis demonstrated that patients with OLK or OSCC exhibit significantly higher rates of vitamin D deficiency and lower serum concentrations compared to healthy controls. Therefore, the assessment of vitamin D status may be considered in clinical practice for individuals with OLK or OSCC.