Dietary and supplemental vitamin D intake and pain interference in adults with chronic spine-related pain: a cross-sectional survey study.

Background/objectives: Chronic spine-related pain is a leading driver of global disability, yet the role of modifiable nutritional factors in relation to functional impairment remains inadequately characterized. This study evaluated the associations between dietary vitamin D exposure ranking, vitamin D supplementation, and pain-related functional interference among adults in tertiary care settings. Methods: A multi-center cross-sectional survey was conducted at four tertiary hospitals in China, including 698 adults with spine-related pain persisting for at least 3 months. Dietary vitamin D intake was operationalized as a standardized ranking index derived from a semi-quantitative food frequency screener. Vitamin D supplementation was categorized by current and regular use. The primary outcome was the Brief Pain Inventory (BPI) interference mean score. Given the observational cross-sectional design, analyses were interpreted as associations rather than causal effects. Multivariable linear regression adjusted for confounders including age, BMI, physical activity, sleep quality, depressive symptoms, and sun exposure proxies. Results: Higher dietary vitamin D index was significantly associated with lower pain interference in the fully adjusted model ( Conclusion: Higher dietary vitamin D exposure ranking and regular supplementation were independently associated with lower functional interference in this chronic spine pain population. Because the study was observational and cross-sectional, the findings should be interpreted as hypothesis-generating associations rather than evidence of therapeutic benefit, particularly in higher-risk phenotypes.