Dietary intake and depressive symptoms: A systematic review of observational studies

Abstract

The importance of research into the possible role of dietary intake in depressive symptoms is emphasized by the fact that diet is modifiable. We systematically reviewed observational studies investigating the association between dietary intake and depressive symptoms published in English as of December 2008. Using the PubMed database, 34 publications (23 cross-sectional, 10 prospective cohort, and 1 case-control studies) were identified. The number of subjects (n 5 80-27 111), age of subjects (15-97 years), dietary assessment method (dietary record, diet history interview, and validated and non-validated dietary questionnaire), depressive symptom assessment (discharge diagnosis, established scale, and self-reported information) varied among studies. Dietary variables most frequently investigated included long chain n-3 PUFA, fish, folate, and other B vitamins. Most studies found no association between dietary variables and depressive symptoms. However, most studies included at least one important methodological limitation, such as no inference for causality, unreliable or rough assessment of diet or depressive symptoms, inadequate treatment of potential confounding factors, and ignorance of the possible mediating or confounding influence of other dietary variables. Further evidence from well-designed observational studies is required to confirm or refute the association between dietary intake and depressive symptoms in freeliving settings.

Intake of dairy products and calcium and prevalence of depressive symptoms during pregnancy in Japan: a cross‐sectional study

“…The dietary factors most commonly examined in observational epidemiological studies regarding this issue include nÀ3 polyunsaturated fatty acids, fish, folate, and other B vitamins, and most studies have found no association between dietary variables and depressive symptoms. 1 In our previous study, significant inverse associations were found between intake levels of fish, eicosapentaenoic acid, docosahexaenoic acid, and vitamin D and the prevalence of depressive symptoms during pregnancy, whereas a significant positive relationship was observed between the intake of saturated fatty acids and the prevalence of depressive symptoms during pregnancy in this population. 2 The possible role of dairy products and calcium in depressive symptoms has received much less attention; moreover, the findings have been inconsistent.…”

Empirically derived dietary patterns in relation to psychological disorders

“…These nutrients might have favourable effects on psychological conditions through reducing serum homocysteine levels as well as through synthesis of monoamines including dopamine and serotonin in the brain (12) . Increased concentrations of serum homocysteine and decreased levels of dopamine and serotonin have been associated with increased risk of depressive disorders (10)(11)(12) . Folate and B vitamins are cofactors in the methylation process of homocysteine to methionine.…”

“…Biases in dietary reporting between men and women might explain this difference by sex. In addition, gonadal hormones might lead to differential responses to possible mediating factors (11) . The present study has several strengths.…”

“…Although not a prominent cause of mortality, depression results in significantly decreased quality of life (8) . Previous studies on diet and psychological disorders have assessed the association between dietary intakes of folate, vitamin B 6 , vitamin B 12 , long-chain fatty acids, Zn and Mg and depression (9)(10)(11)(12)(13)(14)(15) . Limited data are available linking dietary patterns to psychological disorders.…”

“…In addition, earlier studies have mostly focused on depression, and the association between dietary intakes and other psychological disorders like anxiety and psychological distress has not been adequately addressed. Due to the contribution of several nutrients and foods to these conditions (9)(10)(11)(12)(13)(14)(15) , it is expected to find a significant association between major dietary patterns and these disorders. Moreover, previous studies from this region have indicated that the application of statistical methods like factor analysis on dietary data would result in interpretable dietary patterns (20,25,26) ; however, almost all previous reports on dietary patterns from this region have been conducted on small sample sizes.…”