The field of nutritional psychiatry has generated observational and efficacy data supporting a role for healthy dietary patterns in depression onset and symptom management. To guide future clinical trials and targeted dietary therapies, this review provides an overview of what is currently known regarding underlying mechanisms of action by which diet may influence mental and brain health. The mechanisms of action associating diet with health outcomes are complex, multifaceted, interacting, and not restricted to any one biological pathway. Numerous pathways were identified through which diet could plausibly affect mental health. These include modulation of pathways involved in inflammation, oxidative stress, epigenetics, mitochondrial dysfunction, the gut microbiota, tryptophan-kynurenine metabolism, the HPA axis, neurogenesis and BDNF, epigenetics, and obesity. However, the nascent nature of the nutritional psychiatry field to date means that the existing literature identified in this review is largely comprised of preclinical animal studies. To fully identify and elucidate complex mechanisms of action, intervention studies that assess markers related to these pathways within clinically diagnosed human populations are needed.

Numerous observational studies have investigated the role of the Dietary Inflammatory Index (DII®) in chronic disease risk. The aims of this umbrella review and integrated meta-analyses were to systematically synthesize the observational evidence reporting on the associations between the DII and health outcomes based on meta-analyses, and to assess the quality and strength of the evidence for each associated outcome. This umbrella review with integrated meta-analyses investigated the association between the DII and a range of health outcomes based on meta-analyses of observational data. A credibility assessment was conducted for each outcome using the following criteria: statistical heterogeneity, 95% prediction intervals, evidence for small-study effect and/or excess significance bias, as well as effect sizes and P values using calculated random effects meta-analyses. In total, 15 meta-analyses reporting on 38 chronic disease-related outcomes were included, incorporating a total population of 4,360,111 subjects. Outcomes (n = 38) were examined through various study designs including case-control (n = 8), cross-sectional (n = 5), prospective (n = 5), and combination (n = 20) study designs. Adherence to a pro-inflammatory dietary pattern had a significant positive association with 27 (71%) of the included health outcomes (P value < 0.05). Using the credibility assessment, Class I (Convincing) evidence was identified for myocardial infarction only, Class II (Highly suggestive) evidence was identified for increased risk of all-cause mortality, overall risk of incident cancer, and risk of incident site-specific cancers (colorectal, pancreatic, respiratory, and oral cancers) with increasing (more pro-inflammatory) DII score. Most outcomes (n = 31) presented Class III (Suggestive) or lower evidence (Weak or No association). Pro-inflammatory dietary patterns were nominally associated with an increased risk of many chronic disease outcomes. However, the strength of evidence for most outcomes was limited. Further prospective studies are required to improve the precision of the effect size.

The relationship between better diet quality and decreased depression across the life span is consistent and compelling. Fruit and vegetable consumption has been of particular interest. The nutritional benefits from the consumption of fruits and vegetables may mitigate non-communicable diseases and promote brain and mental health. This study aimed to determine whether fruit and vegetable consumption during adolescence was associated with a reduced risk of developing depression in adulthood in a large, representative sample of US individuals. Data from the Add Health Study were analyzed, which included 3,696 participants who were aged approximately 17 years at baseline (1994–1995), and 29 years at follow-up (2007–2008). The Center for Epidemiologic Studies Depression Scale was used to assess depression and a self-report item asked how many times the participant consumed fruit/vegetables on the previous day. Individuals who were depressed at both times points had the highest proportion who failed to consume any fruit (31%) or vegetables (42%) on the previous day. Fruit and vegetable consumption did not predict of adult depression in fully adjusted models. Cross sectional associations existed for diet and adolescent depression only. Our initial findings supported fruit and vegetable consumption as being protective against adult depression, but this association was subsequently attenuated on adjustment for other relevant factors. Future research will benefit from more precise measures of dietary intakes.

No abstract

No abstract

No abstract

Purpose The risk psychological distress (PD) confers on mortality due to specific chronic diseases compared to suicide is unclear. Using the National Health Interview Survey (NHIS), we investigated the association between PD levels and risk of all-cause and chronic disease-specific mortality and compared the contribution of chronic disease-related mortality to that of suicide. Methods Data from 195, 531 adults, who participated in the NHIS between 1997 and 2004, were linked to the National Death Index records through to 2006. Multivariable Cox regression models were used to estimate hazard ratios (HRs) and their 95% confidence intervals (CIs) across four levels of PD, measured using the Kessler-6 scale. Outcomes included all-cause mortality, and mortality due to all CVDs and subtypes, all cancers and subtypes, diabetes mellitus, alcoholic liver disease and suicide. Results During a mean follow-up time of 5.9 years, 7665 deaths occurred. We found a dose–response association between levels of PD and all-cause mortality, with the adjusted HRs (95% CI) elevated for all levels of PD, when compared to asymptomatic levels: subclinical 1.10 (1.03–1.16), symptomatic 1.36 (1.26–1.46) and highly symptomatic 1.57 (1.37–1.81). A similar association was found for all CVDs and certain CVD subtypes, but not for cancers, cerebrovascular diseases diabetes mellitus. Excess mortality attributable to suicide and alcoholic liver disease was evident among those with levels of PD only. Conclusion PD symptoms, of all levels, were associated with an increased risk of all-cause and CVD-specific mortality while higher PD only was associated with suicide. These findings emphasise the need for lifestyle interventions targeted towards improving physical health disparities among those with PD. Supplementary Information The online version contains supplementary material available at 10.1007/s00127-021-02116-7.

No abstract