Abstract
BACKGROUND: Depression is the leading cause of mental health-related diseases and disability. There are different modifiable lifestyle behaviors which contribute to development of common mental disorders among which nutrition has received a considerable attention in recent years. Dietary diversity (DD), an important nutritional factor, is defined as the number of different food groups or foods consumed in a given period. Dietary diversity is an important aspect of diet quality that has not been extensively studied and warrants further investigation. Also results of recent studies are controversial, both on the relationship between dietary diversity and depression and on how dietary diversity may affect depression by its degree of severity. METHODS: We searched electronic data bases of PubMed, Scopus and Web of Science for every result about the relationship between dietary diversity and depression. Inclusion criteria was: 1. All observational studies investigating the effect of DD on depression and depressive symptoms. 2.Adult populations aged 18 years and older and exclusion criteria was: (1) Other studies rather than observational studies (2) Adolescents and children (under 18 years of age) as participants. (3) Pregnant and lactating women. Studies with inadequate data were not included too. RESULTS: 4372 research studies were identified and 9 cross-sectional studies remained to be included in the study. The result of our meta-analysis showed a significant decrease in depression and depressive symptoms due to a more diverse diet (pooled OR: 0.80; 95% CI: 0.74 to 0.88; p = 0.000; I(2=) 96.0%). CONCLUSIONS: This systematic review and meta-analysis showed that a higher DD is inversely associated with depression. The conclusion claims a definitive inverse association between DD and depression. However, the study only includes cross-sectional studies, which cannot establish causality.