How does gut microbiota affect mental health in 18-25 year olds?

In an article recently published in International Journal of Molecular Sciencesscientists described the importance of the gut-small-microbial axis in establishing optimal mental health in emerging adulthood (18-25 years).

Study: Drugs, guts, brains, but not rock and roll: the need to consider the role of the gut microbiota in contemporary mental health and wellness of emerging adults.  Image Credit: Alpha Tauri 3D GraphicsStady: Drugs, guts, brains, but not rock ‘n’ roll: the need to consider the role of the gut microbiota in contemporary mental health and the wellness of emerging adults.. Image Credit: Alpha Tauri 3D Graphics

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Emerging puberty is a critical period for neuronal development, neuroplasticity, and maturation of the hypothalamic-pituitary-adrenal axis. During this period, stress responses, including fluctuations in hormonal levels and varied activation of the hypothalamic-pituitary-adrenal axis, greatly influence the development of mental health. Studies have shown that mental illness occurs more frequently in emerging adults during this period.

The gut microbiota is a group of diverse microorganisms, including bacteria, found in the gastrointestinal tract. Various factors, including genetics, early life factors (mother infection, antibiotic use, etc.), and environmental/lifestyle factors (diet, physical activity, stress, etc.), can significantly alter the composition of The diversity of microorganisms in the intestine.

Recent evidence suggests that emerging adulthood is associated with unique impairments in the gut microbiota. In young adults, the gut microbiota is less diverse, simple, and more stable than in children, adolescents, and the elderly. In the current article, scientists hypothesized that the gut-brain-microbe axis may play a role in determining mental health problems, which are increasing exponentially in Western countries, likely due to unfavorable lifestyle behaviors.

The interface between the gut microbiota and mental health likely depends on several factors.  (a) The first is the inputs to the intestinal tract that form the microbiota accordingly (diet, medications, antimicrobials, etc.).  (b) Periods when germs undergo changes in diversity (alpha) that occur in healthy people, particularly between the late teens and early twenties, which are likely to lead to differences in metabolic output that affect brain health.  (c) The intersection of the adolescent brain, along with the naturally fluctuating age-group microorganisms, promoting desirable microorganisms through physical activity/exercise and circadian rhythm, and undesirable microbiota using different substances.  Part (c) was excerpted from Bian et al.  , 2017. Figure created with Biorender (Accessed 29 April 2022).The interface between the gut microbiota and mental health likely depends on several factors. (a) The first is the input to the intestinal tract that forms the microbiota accordingly (diet, medications, antimicrobials, etc.). (B) Periods when microorganisms go through changes in diversity (alpha) occur in healthy people, particularly between the late teens and early twenties, which are likely to lead to differences in metabolic output that affect brain health. (c) The adolescent brain, along with naturally fluctuating age-group microbes, intersects and promotes desirable microbiota through physical activity/exercise and circadian rhythm, and undesirable microbiota using different substances. part (c) Adapted from Bian et al. , 2017. Figure created with Biorender (Accessed 29 April 2022).

The axis of the small intestine and microbiota

The gut microbiota produces many vital components, such as short-chain fatty acids, brain-derived neurotrophic factors, and neurotransmitters, which mediate gut-brain communication. An imbalance in the gut microbiota can lead to the production of inflammatory cytokines mediated by lipopolysaccharides (LPS), which subsequently affect the hypothalamic-pituitary-adrenal axis by stimulating the afferent vagal nerve.

The effect of the gut microbiota on mental health

According to the available literature, there is a link between gut microbiota and mental health. In this context, studies have shown that antibiotic-induced alteration of the gut microbiota is associated with altered emotional behaviors. The gut-small-microbial axis is known to play an essential role in the development of many neuropsychiatric diseases, including Alzheimer’s disease, Parkinson’s disease, and autism spectrum disorder. Any imbalance in the gut microbiota during the maturation period can lead to a chain of events that have prolonged negative effects on both physical and mental health.

Effect of environmental/lifestyle factors on gut microbiota and mental health

Environmental factors that have the greatest influence on the formation of the gut microbiota include diet, medications, and antimicrobial agents. In addition, physical activity, sleep patterns, and drug use significantly affect the gut microbiota as well as mental health.

Common findings of different types of diet on the gut-brain axis and microbiome.  (a) Diets rich in vegetables, fiber and micronutrients such as vitamins D and C, probiotics, prebiotics, fermented and anti-inflammatory foods rich in omega-3, low in fat and low in carbohydrates promote positive mental health and increase in Bacteroidetes, Prevotella, short chain fatty acids, Bifodobacteria, Akkermansia, Roseburia, Lactilobacillus, and interleukin (IL)-10, is decreased in Firmicutes, Escherichia coli, Ruminococcus, Coprococcus, vascular endothelial growth factor, and monocytes.  Gamma-induced protein 10, IL-17, IL-12, c-reactive protein, IL-2, tumor necrosis factor, and lipopolysaccharide.  (b) Foods high in fat, sugar and ultra-processing increase bacteria, bile acids, pylori, wadsworth, enterobacteriaceae, staphylococcus, escherichia, klebsiella and shigella.  Figure created with Biorender (Accessed April 29, 2022).Common findings of different types of diet on the gut-brain axis and microbiome. (a) Diets rich in vegetables, fiber and micronutrients such as vitamins D and C, probiotics, prebiotics, fermented and anti-inflammatory foods rich in omega-3, low in fat and low in carbohydrates promote positive mental health and increase in Bacteroidetes, Prevotella, short chain fatty acids, Bifodobacteria, Akkermansia, Roseburia, Lactilobacillus, and interleukin (IL)-10, is decreased in Firmicutes, Escherichia coli, Ruminococcus, Coprococcus, vascular endothelial growth factor, and monocytes. Gamma-induced protein 10, IL-17, IL-12, c-reactive protein, IL-2, tumor necrosis factor, and lipopolysaccharide. (b) Foods high in fat, sugar and ultra-processing increase bacteria, bile acids, pylori, wadsworth, enterobacteriaceae, staphylococcus, escherichia, klebsiella and shigella. Figure created with Biorender (Accessed April 29, 2022).

diet

Dietary components greatly influence the composition and diversity of the gut microbiota. Excessive consumption of unhealthy foods (saturated fats, refined sugar, red meat, and low-fiber foods) and low consumption of healthy foods (fruits and vegetables) can lead to microbial dysbacteriosis, which is characterized by alteration in the functional structure, diversity, local distribution, and metabolic activities of gut microbes.

Strong evidence suggests that a diet rich in vegetables, fruits, fiber, fermented foods, vitamins, probiotics, and polyunsaturated fatty acids helps maintain a balanced gut microbiome and promotes positive mental health. In contrast, foods high in fats, carbohydrates, and ultra-processed foods are associated with gut dysfunction, inflammation, and poor mental health.

Physical activity

It is well known that regular physical activity is vital for maintaining cardiovascular and metabolic fitness and improving mental health. Additionally, with respect to gut microbial diversity, physical activity is known to increase levels of beneficial microbes and their gut metabolites.

The effect of physical activity may vary between individuals depending on age, gender, genetic makeup, body mass index, and dietary habits. Notably, intense physical activity can lead to bacterial dysbacteriosis in the gut and infections and cause adverse health consequences. Thus, the optimal level of physical activity should be individual.

use materials

Excessive consumption of nicotine, alcohol, cannabis and illicit substances has frequently been observed in emerging adults, especially those residing in Western countries. These substances are known to have a negative effect on physical and mental health.

The neuronal nicotinic acetylcholine receptors are vital for the development and maturation of the central nervous system. Nicotine consumption in early life can lead to addiction, cognitive decline, and mental disorders. Furthermore, nicotine consumption may disrupt the gut microbiota balance by increasing intestinal mucosal permeability and disrupting mucosal immune responses.

Excessive alcohol consumption in early life can lead to changes in the frontal and temporal lobes of the brain and disrupt neural networks associated with learning, memory, motor speed, attention, executive functioning, and impulsivity. In the gut, alcohol alters metabolic levels, increases inflammation, and disrupts the integrity of the intestinal epithelium.

Cannabis consumption increases cannabinoid receptor activity and leads to various health outcomes, including stimulation of gastric acid secretion, reduced intestinal motility, and stimulation of intestinal permeability and inflammation. Furthermore, studies have shown that cannabis use at a young age is associated with lower cognitive abilities.

sleep pattern

Regular sleep patterns can be affected by certain factors, including shift work, exposure to light at night, inconsistent eating timing, unhealthy eating, and jet lag. A shift in sleep timing and pattern is most commonly observed among adolescents, linked to mental disorders such as depression and anxiety.

Disruption of sleep patterns can also disrupt the homeostasis of the gut microbiome by increasing harmful microbes and decreasing beneficial microbes and their metabolites.

Journal reference:

  • Lee Ji. 2022. Drugs, guts, brains, but not rock ‘n’ roll: the need to consider the role of the gut microbiota in contemporary mental health and wellness of emerging adults. International Journal of Molecular Sciences. https://www.mdpi.com/1422-0067/23/12/6643

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