Association between daily dietary intake trajectory and depressive symptom onset and transition among young adults: a longitudinal study

Little information is available on long-term dietary monitoring among young adults. We examined the associations between 28-month dietary intake trajectories and depressive symptom onset and transition. Using complete daily dining records from Shanghai's Intelligent Ordering System (IOS) (September 2021–December 2023; n = 6,447), we prospectively assessed dietary exposures prior to measuring depressive symptoms through two Beck Depression Inventory-II (BDI-II) administrations at 24-month intervals (2022 and 2024) in young adults aged 18–40 years. Group-based multi-trajectory models (GBMTs) identified monthly dietary trajectories (classified as Chronic Recommended, Chronic High/Low, or Fluctuating) for 28 nutrients and 15 food components. Multivariable logistic regression assessed associations with depressive symptom onset/transition. Among 6447 young adults, depressive symptom incidence was 9.7%, whereas depressive symptom improvement and progression incidences were 59.1% and 12.52%, respectively. Certain nutrient and food component trajectories were associated with lower depressive symptom onset risk, including chronic higher intake of carbohydrates, protein, sodium, oil, and sauce, and chronic lower intake of saturated fatty acids (SFAs). In contrast, non-recommended trajectories of zinc, refined grains, and light-colored vegetables were linked to higher onset risk. Notably, some trajectories (e.g., high fat, potassium) showed dual associations: they correlated with higher chances of depressive symptom improvement but also elevated progression risk. Certain nutrients and dietary patterns showed protective effects against depressive symptom onset, while non-recommended trajectories increased the risk. Some patterns improved symptoms but increased progression risk. The nutritional medicine approach may be beneficial for preventing and promoting depression in young adults.