Relationships between dietary antioxidant capacity, systemic redox balance, and neuropathic pain after spinal cord injury.

STUDY DESIGN: Cross-sectional study. OBJECTIVES: To investigate the relationship between dietary antioxidant capacity, serum oxidant/antioxidant status, and neuropathic pain in individuals with chronic spinal cord injury (SCI). SETTING: Tertiary Rehabilitation Hospital. METHODS: Individuals aged 18-65 years with chronic traumatic SCI were included. Participants were classified by neuropathic pain status into SCI_NeuP (DN4 ≥ 4) and SCI_no-NeuP (DN4 < 4; pain-free at assessment, NRS = 0). Pain severity and pain interference were assessed using the Brief Pain Inventory. Dietary intake was evaluated via face-to-face interview using a semi-quantitative food frequency questionnaire, and dietary total antioxidant capacity (dTAC) was calculated using the Ferric Reducing Antioxidant Power database. To account for total energy intake, dTAC was expressed per 1000 kcal (dTAC/1000 kcal). Fasting serum total antioxidant status (TAS) and total oxidant status (TOS) were measured. The prespecified primary analysis was multivariable linear regression within SCI_NeuP with pain severity as the primary outcome; pain interference was a secondary outcome. RESULTS: Sixty-six participants were included (SCI_NeuP n = 33; SCI_no-NeuP n = 33). In SCI_NeuP, higher dTAC/1000 kcal was independently associated with lower pain severity (B = -1.655, 95% CI - 3.124 to -0.187; p = 0.029). dTAC/1000 kcal was not significantly associated with pain interference (B = -1.559, 95% CI - 3.412-0.294; p = 0.096). Serum TAS and serum TOS were not significantly associated with pain outcomes (all p > 0.05). CONCLUSIONS: Higher energy-adjusted dietary antioxidant capacity was associated with lower neuropathic pain severity after SCI, whereas no independent associations were observed for pain interference or serum TAS/TOS.