Diet and Mental Health: Review of the Recent Updates on Molecular Mechanisms

Abstract

Over the last decades, there has been a substantial increase in the prevalence of mental health disorders, including an increased prevalence of depression, anxiety, cognitive, and sleep disorders. Diet and its bioactive components have been recognized among the modifiable risk factors, possibly influencing their pathogenesis. This review aimed to summarize molecular mechanisms underlying the putative beneficial effects toward brain health of different dietary factors, such as micro- and macronutrient intake and habits, such as feeding time and circadian rhythm. The role of hormonal homeostasis in the context of glucose metabolism and adiponectin regulation and its impact on systemic and neuro-inflammation has also been considered and deepened. In addition, the effect of individual bioactive molecules exerting antioxidant activities and acting as anti-inflammatory agents, such as omega-3 fatty acids and polyphenols, considered beneficial for the central nervous system via modulation of adult neurogenesis, synaptic and neuronal plasticity, and microglia activation has been summarized. An overview of the regulation of the gut-brain axis and its effect on the modulation of systemic inflammation and oxidative stress has been provided. Finally, the impact of bioactive molecules on inflammation and oxidative stress and its association with brain health has been summarized.

Keywords: brain; depression; diet; inflammation; mental health; neuronal plasticity; neurons; oxidative stress; polyphenols; sleep.

Figure 1

Neuroendocrine mechanisms of omega-3 polyunsaturated fatty acids effect on the central nervous system.

Figure 2

Schematic illustration of gut–brain communication through systemic involvement. (A) In physiologic conditions, the gut is able to transmit signals at systemic level by activation of enteroendocrine cells (EECs) and enterochromaffins cells (ECCs): EECs are responsible for secretion of various circulating hormones (i.e., glucagon-like peptides (GLPs), peptide tyrosine tyrosine (PYY), oxyntomodulin); ECCs are responsible for direct neuronal signaling through vagal or afferent nerve fibers by controlling serotonin release. (B) Modification of gut microbiota, such as a decrease in commensal Bifidobacterium and Lactobacillus strains and increase in Bacteroides/Prevotella species, may lead to a reduction of short-chain fatty acids (SCFAs) including acetate, propionate, and butyrate and hyper-secretion of lipopolysaccharides (LPS) that bind to circulating monocyte and macrophages, which, in turn, stimulate the secretion of pro-cytokines (TNF-a, IL-1, IL-6).