Oxidative stress and inflammatory factors mediate the association between dietary antioxidant intake and depressive symptoms in middle and old-aged individuals: A cross-sectional study from NHANES.

Background: The relationship between dietary antioxidant intake and depression remains controversial. This study aimed to explore the intermediary role of oxidative stress and inflammatory markers in linking dietary antioxidant intake to depression among middle-aged and older adults.

Methods: This is a cross-sectional study from the 2003-2014 National Health and Nutrition Examination Survey (NHANES), depressive symptoms were identified using a score of 10 or above on the Patient Health Questionnaire-9 (PHQ-9). Dietary antioxidant intake was measured via the Composite Dietary Antioxidant Index (CDAI). We utilized multivariable logistic regression to assess the link between CDAI and depression risk, followed by mediation analysis to explore the potential mediating effects of oxidative stress and inflammatory markers.

Results: In the multivariate analysis, a robust inverse relationship was noted between the Composite Dietary Antioxidant Index (CDAI) and depression risk, with participants in the upper CDAI tertile demonstrating a 36 % reduced risk compared to those in the lower tertile (OR: 0.64, 95 % CI: 0.53-0.79; P < 0.001). The relationship was nearly linear, as indicated by restricted cubic splines. Furthermore, higher CDAI scores were linked to lower depression scores (β = -0.03, 95 % CI: -0.05 to -0.01; P < 0.001). Mediation analysis indicated that GGT, albumin, and the systemic immune-inflammation index (SII) accounted for 4.6 %, 6.3 %, and 6.1 % of the CDAI-depression association, respectively, with a total mediated effect of 11.4 % (all P < 0.001).

Conclusion: The CDAI exhibits a significant negative association with depression, potentially mediated by oxidative stress and inflammation among middle-aged and older adults.