Total protein, plant protein, animal protein, and specific animal protein sources intake in relation to risk of depression: a systematic review and meta-analysis of observational studies.

To elucidate the relationships between overall, plant-derived, animal-derived, and specific animal-based protein categories and the risk of depression. We searched PubMed, Scopus, and Web of Science up to March 2026. We identified 21 cohort and 49 cross-sectional studies. In cohort studies, higher intakes of plant protein and fish were associated with lower depression risk (RR: 0.87; 95% CI: 0.78-0.97 and 0.92; 95% CI: 0.86-0.99). Processed meat and total meat intake were associated with increased risk (RRs: 1.02; 95% CI: 1.01-1.04 and 1.21; 95% CI: 1.03-1.42). Cross-sectional analyses showed inverse associations for total protein (RR 0.64; 95% CI: 0.43-0.95), plant protein (RR 0.89; 95% CI: 0.81-0.98), poultry (RR 0.87; 95% CI: 0.78-0.98), and fish (RR 0.85; 95% CI: 0.76-0.95). Dose-response analyses indicated that higher intakes of eggs, total protein, and dairy were associated with lower depression risk. Overall, higher intakes of plant-based proteins, fish, poultry, and total protein may be associated with a lower risk of depression, whereas greater consumption of total and processed meats may be associated with a higher risk. However, these findings should be interpreted cautiously given the observational and, for some analyses, cross-sectional nature of the included studies, along with heterogeneity in dietary and depression assessment methods.Registration: This study was registered at PROSPERO (CRD42022352303).