The association between plant and animal protein intake with depression, anxiety, and stress.

Background: Recent evidence suggests that diet composition is a key biological factor related to the development of depressive disorders. The present study was conducted to investigate the animal and plant protein intake and their replacement in association with depression, anxiety, and stress in Iranian adults.

Method: In this cross-sectional study, the dietary intake of 7169 subjects were assessed using a validated food frequency questionnaire. The depression, anxiety, and stress Scale - 21 (DASS-21) questionnaire was used to psychological disorders. Logistic regression was used to obtain odds ratios for depression, anxiety, and stress across quintiles of animal and plant protein.

Results: The participants' age range was 20-69 years. Individuals with the highest animal protein consumption had a lower chance for developing depression compared to those with the lowest intakes (OR = 0.73, 95%CI: 0.59-0.90; P_trend< 0.01). Results also showed a significant association between animal protein intake and anxiety, such that subjects in the highest quintile of animal protein intake had 24% lower odds for anxiety compared to those in the lowest quintile (p < 0.05). We found a significant association between highest quintiles of animal protein intake and a 40% lower risk for stress among female individuals (P_trend= 0.05). The multivariable-adjusted non-linear analyses also revealed that the replacement of plant protein with animal protein was significantly associated with the likelihood of depression and anxiety (P < 0.05).

Conclusion: Animal protein intake might lower the odds of depression and anxiety particularly. Future prospective investigations are proposed to confirm these findings.