The Association Between Fermented Food Intake and Hs-CRP Across Age Groups in Korean Adults: Effect Modification by...

Background/Objectives: Korean traditional fermented foods may confer metabolic and anti-inflammatory benefits; however, their high sodium content raises concerns, particularly given age-related differences in sodium sensitivity. This study examined age-specific associations between fermented food intake and high-sensitivity C-reactive protein (hs-CRP), a marker of low-grade systemic inflammation, and assessed whether sodium intake modifies these associations. Methods: Data from KNHANES 2015-2018 were used to analyze 17,984 adults. Fermented foods were categorized into 10 groups (grains, jang, vinegars, vegetables, fish, fruits, dairy, alcoholic beverages, sauces, and tea/beverages). Intake (% of total energy) was classified into quartiles. Elevated hs-CRP was defined as ≥1 mg/L. Complex-sample multivariable logistic regression was used to assess age-stratified associations and interactions with total sodium and fermented food-derived sodium (SPSS 29.0; p < 0.05). Results: Fermented food intake decreased with age (p < 0.001). In adults aged 20-39, higher intake was associated with lower odds of elevated hs-CRP (Q4 vs. Q1: OR = 0.699, 95% CI 0.542-0.901; p for trend = 0.002). A similar inverse association was observed in those aged 40-64 (Q4: OR = 0.817, 95% CI 0.691-0.967; p for trend = 0.006), which remained significant after adjustment for fermented food-derived sodium. Among adults ≥65, significant interactions were observed for both fermented food-derived sodium (p = 0.040) and total sodium (p = 0.042), indicating variation across sodium intake levels. Conclusions: The association between fermented food intake and systemic inflammation differs by age. In older adults, this relationship appears to be modified by dietary sodium context, highlighting the importance of age-specific dietary considerations.