Context: Emerging evidence indicates that nutrition is important for the onset of depression. However, studies on the link between protein intake and depression risk have produced mixed results.
Objective: We conducted a systematic review and dose-response meta-analysis in adults to summarize the relationship between dietary protein intake and risk of depression.
Data sources: A comprehensive literature search was conducted in Scopus, Clarivate Web of Science, and PubMed/Medline until August 2024. Additionally, a manual search was conducted in Google Scholar.
Data extraction: We included studies that reported relative risks (RRs), odds ratios (ORs), or hazard ratios (HRs), along with 95% CIs of depression (excluding depression during pregnancy or postpartum depression) across various values of dietary protein intake in adults.
Data analysis: Thirteen cross-sectional studies were identified. The highest vs lowest total protein intake (OR, 0.56; 95% CI, 0.34-0.92) was related to a lower risk of depression, while animal protein (OR, 0.87; 95% CI, 0.61-1.23) and plant protein (OR, 0.91; 95% CI, 0.69-1.20) did not have any significant association. Additionally, the linear dose-response analysis indicated that each 10% energy increment in total and plant protein intake was associated with 21% and 25% risk reduction for depression, respectively. Moreover, nonlinear dose-response analysis revealed a significant risk reduction for depression while increasing the total, and plant protein intakes.
Conclusion: A negative dose-dependent association was found between total and plant protein intake and depression risk in adults. Future longitudinal studies are needed to clarify the direction of the protein intake-depression relationship and establish the ideal protein intake levels to prevent depression.
Systematic review registration: PROSPERO registration No. CRD42024555661.
Keywords: adults; depression; dietary protein; meta-analysis; systematic review.
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