1.
Evolution of the Human Diet and Its Impact on Gut Microbiota, Immune Responses, and Brain Health.
González Olmo, BM, Butler, MJ, Barrientos, RM
Nutrients. 2021;13(1)
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One explanation for the increased prevalence in chronic disease and mental illness is from the evolutionary perspective. This suggests the rapid shift in diet towards processed foods in the past 200 years has not allowed for sufficient adaptation of the gut microbiome. The gut microbiome plays an important role in the digestive, immune and nervous systems via the gut-brain axis, and may be a key factor in modulating inflammation and disease. The aim of this review is to discuss how what we eat affects the immune system and impacts our brain health. The literature currently shows significant associations between the Western diet and its impact on the health of the gut microbiome and the brain. Increased intake of saturated fats, refined carbohydrates and sugar, coupled with a reduction in fiber, negatively impacts the digestive system and elicits an immune response. This response can lead to neuroinflammation, which is now found to be associated with deficits in learning and memory, as well as increased rates of neurodegenerative disease and depression. Based on the existing literature, the authors conclude the human gut microbiome has not had sufficient time to adapt to many modern foods, thus leading to inflammation and disease. The authors recommend that a diet composed of natural whole foods with minimal processing can help prevent and alleviate some of the burden caused by chronic disease, and suggest future studies focus on improving techniques to evaluate neuroinflammation in humans.
Abstract
The relatively rapid shift from consuming preagricultural wild foods for thousands of years, to consuming postindustrial semi-processed and ultra-processed foods endemic of the Western world less than 200 years ago did not allow for evolutionary adaptation of the commensal microbial species that inhabit the human gastrointestinal (GI) tract, and this has significantly impacted gut health. The human gut microbiota, the diverse and dynamic population of microbes, has been demonstrated to have extensive and important interactions with the digestive, immune, and nervous systems. Western diet-induced dysbiosis of the gut microbiota has been shown to negatively impact human digestive physiology, to have pathogenic effects on the immune system, and, in turn, cause exaggerated neuroinflammation. Given the tremendous amount of evidence linking neuroinflammation with neural dysfunction, it is no surprise that the Western diet has been implicated in the development of many diseases and disorders of the brain, including memory impairments, neurodegenerative disorders, and depression. In this review, we discuss each of these concepts to understand how what we eat can lead to cognitive and psychiatric diseases.
2.
Dietary Neurotransmitters: A Narrative Review on Current Knowledge.
Briguglio, M, Dell'Osso, B, Panzica, G, Malgaroli, A, Banfi, G, Zanaboni Dina, C, Galentino, R, Porta, M
Nutrients. 2018;10(5)
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Neurotransmitters (NTs) are chemical messengers, found mainly within the nervous system. Common NTs are acetylcholine (ACh), glutamate, γ-aminobutyric acid (GABA), dopamine, serotonin (5-HT), and histamine. Many foods are natural sources of NTs that may influence the nervous system, and therefore mood and mental health. This review paper looked at books and studies and discusses the NT content of foods and the possible implications for human health. Acetylcholine is a NT involved in muscle movement, learning and memory. Its presence is documented in more than 50 plant species, including squash, aubergine spinach and nettles. Glutamate is the most abundant excitatory NT in the brain. Glutamic acid naturally occurs in foods with high protein content. Seaweeds, cheeses, fish sauces, soy sauces, fermented beans, and tomato showed high levels of free glutamic acid. Dried cod, salami, caviar, and instant coffee powder are other sources of this amino acid. Salts of glutamic acid, such as monosodium glutamate, are added to certain foods as flavour enhancers. GABA is a calming NT. Studies have found the highest contents of GABA in raw spinach, potato, sweet potato and cruciferous vegetables such as kale and broccoli. Shiitake mushrooms and chestnuts also contained a significant amount of GABA. Dopamine plays an essential role in the coordination of body movements, motivation, and reward. Information on the content of dopamine foods is very limited. Bananas, plantains and avocado were reported to contain high levels of dopamine. 5-HT pathways modulate behaviours, eating, and sleep, and in the gut are involved in the regulation of gastrointestinal motility. In recent years, the number of studies on the content of 5-HT in plants has increased. 5-HT appeared to be prevalent in the green bananas, with higher concentrations found in the peel compared with the flesh. 5-HT was also found in peppers, paprika, hazelnut, tomatoes, pineapple, plum, passion fruit, papaya and kiwi fruit. Histamine is involved in arousal, attention, and reactivity, as well as in local immune responses. The presence of histamine in processed foods, such as aged cheeses, contributes to characteristic flavours and textures. Wine and beer may contain a significant amount of histamine. Fermented foods contain histamine. The food industry generally aims to maintain the levels of amines in foods as low as possible; consumption of fish, cured meat products, sauerkraut, and cheese varieties such as Cheddar, Swiss, Gruyère, and Gouda have been associated with amine poisoning. The significance of dietary NTs intake needs to be further investigated, as there is little data about their bioavailability or clinical implications. New studies should consider if dietary NTs can be transported across the blood-brain barriers or act on the central nervous system via other organs. The authors suggest that in future, including or excluding particular foods containing NTs could be beneficial for patients suffering from Alzheimer’s disease or dementia (an ACh diet), epilepsy or migraines (a glutamate-free diet), anxiety or insomnia (a GABA diet), Parkinson’s disease (a dopamine diet), depressive disorders (a serotonin diet), and vascular headaches (a histamine-free diet).
Abstract
Foods are natural sources of substances that may exert crucial effects on the nervous system in humans. Some of these substances are the neurotransmitters (NTs) acetylcholine (ACh), the modified amino acids glutamate and γ-aminobutyric acid (GABA), and the biogenic amines dopamine, serotonin (5-HT), and histamine. In neuropsychiatry, progressive integration of dietary approaches in clinical routine made it necessary to discern the more about some of these dietary NTs. Relevant books and literature from PubMed and Scopus databases were searched for data on food sources of Ach, glutamate, GABA, dopamine, 5-HT, and histamine. Different animal foods, fruits, edible plants, roots, and botanicals were reported to contain NTs. These substances can either be naturally present, as part of essential metabolic processes and ecological interactions, or derive from controlled/uncontrolled food technology processes. Ripening time, methods of preservation and cooking, and microbial activity further contributes to NTs. Moreover, gut microbiota are considerable sources of NTs. However, the significance of dietary NTs intake needs to be further investigated as there are no significant data on their bioavailability, neuronal/non neuronal effects, or clinical implications. Evidence-based interventions studies should be encouraged.
3.
Zinc, Magnesium, Selenium and Depression: A Review of the Evidence, Potential Mechanisms and Implications.
Wang, J, Um, P, Dickerman, BA, Liu, J
Nutrients. 2018;10(5)
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Adequate micronutrient consumption and mental health are of major public health importance. Recent findings suggest micronutrient deficiencies may play a role in the development and progression of depression, yet the findings remain unclear. The aim of this review is to present the recent evidence on the association between several micronutrients and depression and discuss the potential mechanisms and clinical implications. Based on the current literature, evidence shows an association between both zinc and magnesium deficiency and the risk of depression, with stronger evidence supporting zinc. Studies on selenium are limited or inconclusive. According to these findings, the authors support the importance of adequate micronutrient consumption for promoting mental health. They suggest future research should investigate the safety and efficacy of micronutrient supplementation as an adjunct treatment for depression to better inform current prevention and treatment strategies.
Abstract
Micronutrient deficiency and depression are major global health problems. Here, we first review recent empirical evidence of the association between several micronutrients—zinc, magnesium, selenium—and depression. We then present potential mechanisms of action and discuss the clinical implications for each micronutrient. Collectively, empirical evidence most strongly supports a positive association between zinc deficiency and the risk of depression and an inverse association between zinc supplementation and depressive symptoms. Less evidence is available regarding the relationship between magnesium and selenium deficiency and depression, and studies have been inconclusive. Potential mechanisms of action involve the HPA axis, glutamate homeostasis and inflammatory pathways. Findings support the importance of adequate consumption of micronutrients in the promotion of mental health, and the most common dietary sources for zinc and other micronutrients are provided. Future research is needed to prospectively investigate the association between micronutrient levels and depression as well as the safety and efficacy of micronutrient supplementation as an adjunct treatment for depression.