Associations between food processing levels and depressive symptoms: A cross-sectional study using the Korea National...

Consumption of processed foods has been steadily increasing in modern societies, raising concerns about their potential mental health effects.

This study aimed to investigate the association between food processing levels and depressive symptoms in a nationally representative sample of Korean adults and to explore potential biological mechanisms involving systemic inflammation.

We analyzed data from 18,213 Korean adults (≥19 years) from the 2014-2020 KNHANES. Dietary intake, assessed via 24-hour recall and categorized by the NOVA classification, was used to estimate minimally processed food (MPF) and ultra-processed food (UPF) intake as percentages of total food and energy. Depressive symptoms were measured with the PHQ-9. Associations were examined using multivariable regression models, with item-level and exploratory indirect effect analyses conducted to explore symptom specificity and the role of systemic inflammation (via CRP) in a subsample.

In continuous models, higher MPF intake was associated with lower depressive symptoms (β = -0.040, 95% CI: -0.077 to -0.003), whereas UPF intake showed a positive association (β = 0.081, 95% CI: 0.032 to 0.130), with less consistent patterns in quartile-based analyses. Exploratory item-level analyses suggested associations with cognitive-affective symptoms that did not survive correction for multiple comparisons, while systemic inflammation statistically accounted for approximately 11.7% of the UPF-depressive symptom association.

In this nationally representative study, higher UPF intake was associated with greater depressive symptoms, while MPF intake showed an inverse relationship. These modest, exploratory findings warrant prospective and interventional studies examining the role of dietary modification in mental health.