Dietary Inflammatory Index and Depressive Symptoms in Chinese University Students Leveraging an Intelligent Ordering System: 3-Year Longitudinal Prospective Cohort Study.

backgroundDepression is a major global cause of disability, and depressive symptoms are highly prevalent and increasing among Chinese university students. Mounting evidence confirms that inflammation plays a key role in the pathogenesis of depression, and dietary inflammatory potential regulates systemic inflammation to influence depressive symptom development. However, existing research is limited by cross-sectional designs, recall bias from self-reported dietary surveys, and a lack of long-term prospective cohort evidence on the diet-inflammation-mental health pathway in Chinese university students.

objectiveThis study aimed to examine the longitudinal association between Dietary Inflammatory Index (DII) and the incidence of depressive symptoms in Chinese university students, and to explore subgroup differences by family relationship and socioeconomic status.

methodsA 3-year longitudinal prospective cohort study was conducted among 5314 students from a university in Shanghai, China. Eligible participants met the criteria of ≥86 days of annual campus cafeteria dining and at least 1 breakfast, lunch, and dinner in campus canteens per quarter; students with abnormal monthly energy intake, excessive food consumption, or incomplete 3-year dietary/psychological data were excluded. Dietary data were continuously collected via the Intelligent Ordering System (IOS) from April 2020 to March 2023 to calculate DII scores. Depressive symptoms were annually assessed using the Beck Depression Inventory-II from March 2021 to March 2023. Mixed-effects logistic regression (α=.05) was used to analyze the association, with subgroup analyses stratified by family relationship and poverty status.

resultsThe baseline prevalence of depressive symptoms was 10.75% (571/5314; male: 261/2679, 9.74%; female: 310/2635, 11.76%). After adjusting for covariates, compared with the highest DII quartile (most proinflammatory diet), lower DII quartiles (more anti-inflammatory or low proinflammatory diets) were associated with a reduced risk of incident depressive symptoms in participants without depressive symptoms at baseline: Q1 (odds ratio [OR] 0.27, 95% CI 0.16-0.47), Q2 (OR 0.52, 95% CI 0.33-0.84), and Q3 (OR 0.26, 95% CI 0.16-0.42). Subgroup analyses showed this protective effect was only significant in students with harmonious family relationships and non-poverty-stricken students; no significant association between DII and depressive symptom improvement was found in participants with baseline depressive symptoms.

conclusionsThis study is among the first to prospectively examine dietary inflammatory potential and depressive symptoms in university students using long-term objective dietary monitoring. Unlike studies relying on self-reported dietary surveys, this study used an automated and precise campus-based IOS to continuously capture real-world dietary behaviors over 3 years. The findings indicate that sustained anti-inflammatory dietary patterns are associated with a lower risk of depressive symptoms among Chinese university students, although this protective effect was weaker in students experiencing family discord or socioeconomic disadvantage. These findings provide new longitudinal evidence for the diet-inflammation-mental health relationship and support integrated campus interventions combining dietary guidance with psychosocial support.