Nutritional Biomarkers, Bone Turnover, and Oxidative DNA Damage in Postmenopausal Women with Periodontitis: A Cross-Sectional Study

<b>Background/Objectives:</b> Periodontitis and low BMD often occur after menopause, but the role of nutritional status in the oral-skeletal link is unclear. This study examined whether nutritional biomarkers relate to periodontitis severity and modify the relationship between low BMD and periodontal destruction in postmenopausal women. <b>Methods:</b> This cross-sectional study included 120 postmenopausal women who underwent comprehensive periodontal measurements at six sites per tooth and were classified according to the 2017 World Workshop staging and grading framework. Areal BMD was measured using dual-energy X-ray absorptiometry (DXA). Objective biomarkers included serum 25(OH)D, plasma vitamin C, RBC omega-3 index, and serum ferritin. Mechanistic measures were serum CTX, P1NP, and urinary 8-OHdG/creatinine. The main periodontal outcome was the mean CAL. <b>Results:</b> Low BMD was associated with greater periodontal destruction (mean CAL 2.06 vs. 1.45 mm; adjusted β = 0.664 mm, 95% CI 0.465-0.863; <i>p</i> < 0.001). Higher 25(OH)D and omega-3 index were independently associated with lower mean CAL (β = -0.024 mm per 1 ng/mL and β = -0.107 mm per 1%, respectively), with false discovery rate control applied across nutritional biomarkers. Across the cohort, serum 25(OH)D showed a weak inverse correlation with CTX (<i>r</i> = -0.14; <i>p</i> = 0.141), and exploratory mediation analyses suggested only small indirect effects via CTX and 8-OHdG. <b>Conclusions:</b> In women after menopause, lower BMD is associated with greater periodontal tissue loss. Objective nutritional biomarkers, especially 25(OH)D and omega-3 levels, correlate with biologically plausible pathways involved in periodontal destruction and remodeling. This supports the idea that nutrition could be a key factor linking oral health and skeletal health.