Diet and depression: exploring the biological mechanisms of action

Abstract

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.

Associations of Dietary Intake on Biological Markers of Inflammation in Children and Adolescents: A Systematic Review

“…The mechanisms by which these healthful dietary patterns affect the inflammatory process are largely underexplored [ 18 ]. It has been hypothesised that the protective effect of these patterns may be derived from the anti-inflammatory properties of their constituents [ 92 ].…”

“…Stressors such as trauma through adverse childhood experiences, psychosocial stress, as well as modifiable lifestyle sources such as limited physical exercise or smoking are all capable of evoking a deleterious inflammatory response. Increasingly, attention has been given to diet quality as a potential mechanism of action that can exacerbate or ameliorate low-grade inflammation and subsequently influence mental health [ 18 , 19 ]. Certainly, healthy dietary patterns of high quality, such as adherence to a Mediterranean Diet [ 20 ], or eating foods such as vegetables and fruit [ 1 ], or macro/micronutrients, such as omega-3 poly-unsaturated fatty acids (PUFAs) [ 21 ] or vitamins C and E [ 22 ], respectively, have been shown to reduce systemic inflammation [ 23 , 24 ].…”

Adiposity in Depression or Depression in Adiposity? The Role of Immune-Inflammatory-Microbial Overlap

“…More importantly, anti-inflammatory bioactive phenolic acids derived from dietary polyphenols have been shown to pass through the BBB and hence, directly influence the brain [83,84]. The introduction of a healthy diet, as an intervention targeting the microbiota, is an established way of alleviating symptoms of metabolic disease [85] and is perceived as an adjunctive method in the treatment of depression [86]. Similarly, exercise and a regular routine appear to be associated with a harmonious bacterial ecosystem [87,88].…”

Feasibility and Acceptability of a Healthy Nordic Diet Intervention for the Treatment of Depression: A Randomized Controlled Pilot Trial

“…A third RCT, employing a similar 3-week diet intervention also showed a significantly greater improvement in depressive symptoms compared to the control group, who were given no instructions regarding diet and asked to return after 3 weeks for follow up [ 13 ]. Although the exact biological mechanisms relating diet to depression are unknown, the evidence, mainly from preclinical studies, suggests that the pathways of inflammation, oxidative stress, epigenetics, the gut microbiota, the hypothalamic-pituitary-adrenal (HPA) axis, and metabolic syndrome, among others, play a role [ 14 ].…”