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Previous research on the link between dietary fiber intake and depression had mixed results. In this study by Saghafian et al. (2023), the authors conducted a meta-analysis of electronic databases to find epidemiological research that found dietary fiber intake to be related to depressive and anxiety disorders. Data on dietary fiber consumption with depression or anxiety were included from 18 articles (12 cross-sectional, one case-control, and five cohort studies, up to May 2021). Insufficient data were available to investigate anxiety, while three research on teenagers and 15 studies on adults were done on depression. Analysis of the studies revealed an inverse linear relationship between total dietary fiber intake and risk of depression in adults was found by dose-response meta-analysis. Specifically, each 5-g increase in total dietary fiber intake was linked to a 5% decrease in the risk of depression. Intake of total dietary fiber was linked to a 57% lower risk of depression in adolescents and a 10% reduction in adults. Vegetable fiber consumption and soluble fiber intake were shown to decrease the likelihood of suffering from depression. Insoluble fiber, fruit fiber, and cereal fiber, however, were only tangentially linked to a decline in depression. The authors conclude that a high level of dietary fiber intake helps ameliorate depression in adults in a dose-response manner.

There is considerable overlap between the brain control of stress and the neural regulation of hunger and energy balance. The cortico-limbic striatal system may become dysregulated as a result of recurrent acute stressor exposure, increasing allostatic load (exposure to endocrine or neural responses), and impairment of the integration of postprandial homeostatic and hedonic signals. Bini et al. (2022) underscore the need to comprehend the brain pathways through which stress causes changes in hunger that might result in weight gain. to ascertain the effects of glucocorticoids on the metabolic, neurological, and behavioral elements that may be responsible for the relationship between glucocorticoids, hunger, and the risk of obesity. To measure regional cerebral blood flow (CBF), the authors conducted a randomized, double-blind, cross-over study with hydrocortisone or saline overnight infusion followed by a fasting morning perfusion magnetic resonance imaging. Flyers and online advertisements were used to enlist 16 healthy, slim people (Mean BMI = 22.4 ± 2.2 kg/m2, Mean age = 26.4 ± 6.7 years), whom were assessed for cortisol levels, metabolic hormones, and hunger on the Visual Analog Scale (VAS). Analysis of the results revealed that, In the hypothalamus and associated cortico-striatal-limbic areas, hydrocortisone dramatically reduced whole-brain voxel-based CBF responses compared to saline. Less reduction in CBF (hydrocortisone minus saline) in the medial OFC, medial brainstem and thalamus, left primary sensory cortex, and right superior and medial temporal gyrus predicted hydrocortisone-related increases in appetite. In comparison to saline CBF groups, hydrocortisone significantly increased appetite as measured by the VAS pre-scan, insulin, glucose, and leptin, but not other metabolic hormones. On the hydrocortisone day but not the saline day, hunger evaluations were also strongly correlated with plasma insulin levels. The authors conclude that specific brain networks of prefrontal, emotional, reward, motivation, sensory, and homeostatic regions that underlie control of food intake become affected by increased glucocorticoids at levels similar to those experienced during psychological stress, increasing fasting hunger and decreasing regional cerebral blood flow.

Recent evidence suggests that vegetarian and vegan diets may increase the risk and symptoms of depression, a mental illness that affects 350 million people worldwide. In this systematic review by Jain et al. (2022), the authors investigated the literature available on the association of vegetarian and/or vegan diets with the risk or symptoms of depression, using evidence from observational and intervention studies. Three independent reviewers extracted data, assessed the risk of bias, and performed quality assessments of observational cohorts, cross-sectional studies, and controlled studies using the National Heart, Lung, and Blood Institute of the National Institutes of Health for Quality Assessment of Observational Cohort and Cross-Sectional Studies and Controlled Studies. Following the PRISMA guidelines (Preferred Reporting Items for Systematic Reviews and Meta-analysis), a search was conducted on Medline, Embase, The Cochrane Library, and Web of Science to systematically document relevant cohort, cross-sectional, case-control, or randomized controlled trials examining the association between a vegetarian or vegan diet and depression in adults. Evidence was aggregated and narratively synthesized by type of diet analyzed as vegetarian, vegan, or both. A total of 23 studies (18 cross-sectional, 3 prospective cohorts, and 2 randomized controlled studies) were included in this review with 25 appraisable outcomes. Analysis of the results demonstrated conflicting evidence linking a vegetarian or vegan diet with depression. Seven (28%) outcomes showed a positive effect of diet on depression, while seven (28%) outcomes found no association between vegetarian and vegan diets and depression, although two of the studies found an increased risk of depression in some groups. On the other hand, 11 (48%) outcomes demonstrated a negative impact of vegetarian and vegan diets on the rates of depression. The quality of the evidence was rated as good in four studies and moderate in the remaining 19 studies. The authors conclude that the evidence regarding the effects of vegetarian and vegan diets on depression is conflicting, possibly due to the heterogeneity of the studies analyzed, and that further research is required.

In this study by Mommaerts et al. (2022), the authors evaluated the availability of micronutrients known to be connected to mental health problems in a seven-day cycle menu and supplies available in stores within a prison facility. The nutritional value of the seven-day cycle of meals and four commissary food packets (breakfast, dinner, snacks, and sweets) available for consumption by incarcerated individuals was assessed and compared to dietary reference intakes (DRI). Analysis of the micronutrients demonstrated that DRI guidelines were satisfied for Zinc and vitamins B12, C, and B6 mean values in the menu. However, the DRI guidelines were not met for omega-3 fatty acids, magnesium (for males only), or vitamin D (for both males and females). Because bipolar disorder, anxiety, and depression are known to be exacerbated by deficiencies in vitamin D, magnesium, and omega-3 fatty acids, the authors conclude that modest dietary adjustments could increase the availability and possible consumption of nutrients that may enhance mental health in prison settings.