Ultra-processed food intake and risk of depression: a systematic review / Ingestión de alimentos ultraprocesados y riesgo de depresión: revisión sistemática

Objective: to conduct a systematic review of the observational studies analyzing the association between ultra-processed food (UPF) intake and the risk of depression. Design: the search adhered to the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA); a search for observational studies published until June 2020 was performed in PubMed, Embase, Cochrane Library, and Web of Science databases, followed by additional manual searches. Eight reviewers, working independently in teams of two, screened studies for eligibility, extracted data, and assessed risk of bias. We resolved disagreements through discussion or, if necessary, through adjudication by a third (LH). And the study assessed cross-sectional studies using the Agency for Healthcare Research and Quality (AHRQ) methodological checklist and cohort and case-control studies using the Newcastle-Ottawa Scale (NOS) for quality. We used a tabular format to summarize the articles. Results: twenty-eight studies evaluating UPF intake and risk of depression were finally selected, 21 of which had a cross-sectional design, 6 studies had a cohort design, and 1 had a case-control design. Of these, 4 cohort studies and 17 cross-sectional studies found that consumption of UPF were positively associated with depression or depressive symptoms. Conclusions: our review demonstrated that most studies included in the systematic review showed that UPF consumption is associated with the risk of depression. Future studies should consider the use of validated food intake assessments and standardized depression assessment methods to promote comparability between studies. (AU)

Objetivo: realizar una revisión sistemática de los estudios observacionales que analizan la asociación entre la ingesta de alimentos ultraprocesados (UPF) y el riesgo de depresión. Material y métodos: la búsqueda se adhirió a las directrices Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA); se realizó una búsqueda de estudios observacionales publicados hasta junio de 2020 en las bases de datos PubMed, Embase, Cochrane Library y Web of Science, seguida de búsquedas manuales adicionales. Ocho revisores, que trabajaron de forma independiente en equipos de dos, seleccionaron los estudios para su elegibilidad, extrajeron los datos y evaluaron el riesgo de sesgo. Los desacuerdos se resolvieron a través de la discusión o, si era necesario, a través de la adjudicación de un tercero. Se evaluaron los estudios transversales mediante la lista de comprobación metodológica de la Agency for Healthcare Research and Quality (AHRQ) y los estudios de cohortes y de casos y controles mediante la escala Newcastle-Ottawa (NOS) para la calidad. Se utilizó un formato tabular para resumir los artículos. Resultados: finalmente se seleccionaron 28 estudios que evaluaban la ingesta de UPF y el riesgo de depresión, 21 de los cuales tenían un diseño transversal, 6 un diseño de cohortes y 1 un diseño de casos y controles. De ellos, 4 estudios de cohortes y 17 estudios transversales encontraron que el consumo de UPF se asociaba positivamente con la depresión o los síntomas depresivos. Conclusiones: nuestra revisión demostró que la mayoría de los estudios incluidos en la revisión sistemática mostraron que el consumo de UPF está asociado con el riesgo de depresión. Los estudios futuros deberían considerar el uso de evaluaciones validadas del consumo de alimentos y métodos estandarizados de evaluación de la depresión para promover la comparabilidad entre los estudios. (AU)

Ultra-processed food intake and risk of depression: a systematic review.

Introduction: Objective: to conduct a systematic review of the observational studies analyzing the association between ultra-processed food (UPF) intake and the risk of depression. Design: the search adhered to the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA); a search for observational studies published until June 2020 was performed in PubMed, Embase, Cochrane Library, and Web of Science databases, followed by additional manual searches. Eight reviewers, working independently in teams of two, screened studies for eligibility, extracted data, and assessed risk of bias. We resolved disagreements through discussion or, if necessary, through adjudication by a third (LH). And the study assessed cross-sectional studies using the Agency for Healthcare Research and Quality (AHRQ) methodological checklist and cohort and case-control studies using the Newcastle-Ottawa Scale (NOS) for quality. We used a tabular format to summarize the articles. Results: twenty-eight studies evaluating UPF intake and risk of depression were finally selected, 21 of which had a cross-sectional design, 6 studies had a cohort design, and 1 had a case-control design. Of these, 4 cohort studies and 17 cross-sectional studies found that consumption of UPF were positively associated with depression or depressive symptoms. Conclusions: our review demonstrated that most studies included in the systematic review showed that UPF consumption is associated with the risk of depression. Future studies should consider the use of validated food intake assessments and standardized depression assessment methods to promote comparability between studies.

Introducción: Objetivo: realizar una revisión sistemática de los estudios observacionales que analizan la asociación entre la ingesta de alimentos ultraprocesados (UPF) y el riesgo de depresión. Diseño: la búsqueda se adhirió a las directrices Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA); se realizó una búsqueda de estudios observacionales publicados hasta junio de 2020 en las bases de datos PubMed, Embase, Cochrane Library y Web of Science, seguida de búsquedas manuales adicionales. Ocho revisores, que trabajaron de forma independiente en equipos de dos, seleccionaron los estudios para su elegibilidad, extrajeron los datos y evaluaron el riesgo de sesgo. Los desacuerdos se resolvieron a través de la discusión o, si era necesario, a través de la adjudicación de un tercero. Se evaluaron los estudios transversales mediante la lista de comprobación metodológica de la Agency for Healthcare Research and Quality (AHRQ) y los estudios de cohortes y de casos y controles mediante la escala Newcastle-Ottawa (NOS) para la calidad. Se utilizó un formato tabular para resumir los artículos. Resultados: finalmente se seleccionaron 28 estudios que evaluaban la ingesta de UPF y el riesgo de depresión, 21 de los cuales tenían un diseño transversal, 6 un diseño de cohortes y 1 un diseño de casos y controles. De ellos, 4 estudios de cohortes y 17 estudios transversales encontraron que el consumo de UPF se asociaba positivamente con la depresión o los síntomas depresivos. Conclusiones: nuestra revisión demostró que la mayoría de los estudios incluidos en la revisión sistemática mostraron que el consumo de UPF está asociado con el riesgo de depresión. Los estudios futuros deberían considerar el uso de evaluaciones validadas del consumo de alimentos y métodos estandarizados de evaluación de la depresión para promover la comparabilidad entre los estudios.

Homocysteine-Induced Disturbances in DNA Methylation Contribute to Development of Stress-Associated Cognitive Decline in Rats.

Chronic stress is generally accepted as the main risk factor in the development of cognitive decline; however, the underlying mechanisms remain unclear. Previous data have demonstrated that the levels of homocysteine (Hcy) are significantly elevated in the plasma of stressed animals, which suggests that Hcy is associated with stress and cognitive decline. To test this hypothesis, we analyzed the cognitive function, plasma concentrations of Hcy, and brain-derived neurotropic factor (BDNF) levels in rats undergoing chronic unpredicted mild stress (CUMS). The results showed that decreased cognitive behavioral performance and decreased BDNF transcription and protein expression were correlated with hyperhomocysteinemia (HHcy) levels in stressed rats. Diet-induced HHcy mimicked the cognitive decline and BDNF downregulation in the same manner as CUMS, while Hcy reduction (by means of vitamin B complex supplements) alleviated the cognitive deficits and BDNF reduction in CUMS rats. Furthermore, we also found that both stress and HHcy disturbed the DNA methylation process in the brain and induced DNA hypermethylation in the BDNF promoter. In contrast, control of Hcy blocked BDNF promoter methylation and upregulated BDNF levels in the brain. These results imply the possibility of a causal role of Hcy in stress-induced cognitive decline. We also used ten-eleven translocation (TET1), an enzyme that induces DNA demethylation, to verify the involvement of Hcy and DNA methylation in the regulation of BDNF expression and the development of stress-related cognitive decline. The data showed that TET1-expressing viral injection into the hippocampus inhibited BDNF promoter methylation and significantly mitigated the cognitive decline in HHcy rats. Taken together, novel evidence from the present study suggests that Hcy is likely involved in chronic stress-induced BDNF reduction and related cognitive deficits. In addition, the negative side-effects of HHcy may be associated with Hcy-induced DNA hypermethylation in the BDNF promoter. The results also suggest the possibility of Hcy as a target for therapy and the potential value of vitamin B intake in preventing stress-induced cognitive decline.