In a recently published article International Journal of Molecular Sciencesscientists have described the importance of the gut-brain-microbiota axis in establishing optimal mental health in growing adulthood (18-25 years).
Study: Drugs, guts, brains, but not rock and roll: The role of the intestinal microbiota in contemporary mental health and well-being in adults should be considered. Image Credit: Alpha Tauri 3D Graphics
The emerging adulthood is a critical period for neuronal development, neuroplasticity, and maturation of the hypothalamic-pituitary-adrenal axis. During this period, stress responses, including fluctuations in hormone levels and multiple activations of the hypothalamic-pituitary-adrenal axis, significantly affect the development of mental health. Research has shown that mental illness is a common occurrence in adults during this period.
The intestinal microbiota is a collection of various microorganisms that live in the gastrointestinal tract, including bacteria. A number of factors, such as genetic factors, early life factors (maternal infection, use of antibiotics, etc.) and environmental / lifestyle factors (diet, physical activity, stress, etc.), can significantly alter the composition and diversity of the intestinal microbiota.
Recent evidence suggests that emerging adulthood is associated with a particular vulnerability in intestinal microbes. In emerging adults, the intestinal microbiota is less diverse, simple, and more unstable than in children, adolescents, and the elderly. In the present article, scientists have hypothesized that the intestinal brain-microbiota axis may play a role in determining mental health problems, which are growing significantly in western countries, most likely due to inappropriate lifestyle behaviors.
The interface between intestinal microbiota and mental health is likely to depend on a number of factors. (A) The first is the intakes of the intestinal tract that adapt to this microbiota (diet, medication, antimicrobial, etc.). (B) Periods in which microbiotics undergo changes in diversity (alpha) occur in healthy people, especially in the late teens and thirties, and are likely to cause differences in metabolic products that affect brain health. (C) The intersection of the adolescent brain, combined with the normally variable age group microbiota, to promote a desirable microbiota through physical activity / exercise and circadian rhythm and a desirable microbiota that is not using different substances. part (C) Adapted from Bian et al., Image created with Biorender 2017. (accessed 29 April 2022).
The gut-brain-microbiota axis
Microorganisms that live in the gut produce a number of key components, such as short-chain fatty acids, brain-derived neurotrophic factors, and neurotransmitters that guide communication between the gut and the brain. Intestinal microbiota imbalance can lead to the production of inflammatory cytokines by microbial lipopolysaccharide (LPS) and then affect the hypothalamic-pituitary-adrenal axis by stimulating the afferent vagal nerve.
Influence of intestinal microbiota on mental health
According to the available literature, there is a link between intestinal microbiota and mental health. In this context, research has shown that alteration caused by antibiotics is associated with changes in the gut microbiota’s emotional behavior. The gut-brain-microbiota axis plays a key role in the development of a variety of neurological and psychiatric diseases, including Alzheimer’s disease, Parkinson’s disease, and autism spectrum disorder. Any imbalance in the intestinal microbiota during adulthood can lead to a jump in events that can have long-lasting negative effects on physical and mental health.
Impact of environmental / lifestyle factors on intestinal microbes and mental health
The most influential environmental factors for the formation of intestinal microbiota are diet, medication, and antimicrobial agents. In addition, physical activity, sleep patterns, and substance use have a significant effect on intestinal microbes as well as mental health.
Common findings for different types of bowel-brain-microbiome-focused diets. (A) Vegetables, fiber, micronutrients such as vitamins D and C, probiotics and prebiotics, fermented foods, rich anti-inflammatory omega-3s, low fat and low carbohydrate foods promote and increase positive mental health. Bacteroidetes, Prevotella, short-chain fatty acids, Bifodobacteria, Akkermansia, Roseburia, Lactilobacillus and interleukin (IL) -10, and Firmicutes, Escherichia coli, Ruminococcus, Coprococcus, vascular endothelial growth factor 1, reduced protein interferon gamma-induced protein 10, IL-17, IL-12, c-reactive protein, IL-2, tumor necrosis factor, and lipopolysaccharide. (B) High-fat, high-sugar, and ultra-processed foods increase Bacteroides, Bile Acids, Bilophila wadsworth, Enterobacteriaceae, Firmicutes, Enterobacteriaceae, Escherichia, Klebsiella, and Shigella. Image created with Biorender (acquired April 29, 2022).
The components of the diet significantly affect the composition and diversity of the intestinal microbiota. Excessive consumption of healthy foods (saturated fats, refined sugars, red meat and low-fiber foods) and lower consumption of healthy foods (fruits and vegetables) can cause microbial dysbiosis, which is characterized by a change in functional composition, diversity, local distribution. and metabolic activities of the intestinal microbiota.
There is strong evidence that a diet rich in vegetables, fruits, fiber, fermented foods, vitamins, probiotics, and polyunsaturated fatty acids helps maintain an intestinal microbiota homeostasis and promotes positive mental health. In contrast, high-fat, high-carbohydrate, and ultra-processed foods are associated with intestinal dysbiosis, inflammation, and poor mental health.
It is well known that regular physical activity is essential for maintaining metabolic and cardiovascular fitness and improving mental health. Furthermore, in terms of intestinal microbial diversity, it is well known that physical activity increases the level of beneficial intestinal microbes and metabolites.
The impact of physical activity can vary between people depending on age, gender, genetic makeup, body mass index (BMI), and dietary habits. Notably, intense physical activity can cause intestinal microbiota dysbiosis and inflammation and can have adverse health effects. Therefore, the optimal level of physical activity must be individualized.
Excessive consumption of nicotine, alcohol, cannabis, and illegal substances has often been seen in rising adults, especially those living in Western countries. These substances are known to have a negative effect on both physical and mental health.
Neurotic nicotinic acetylcholine receptors are essential for the development and maturation of the central nervous system. Early nicotine use can lead to addiction, cognitive decline, and psychiatric disorders. In addition, nicotine consumption can cause intestinal microbiota imbalance, increasing the permeability of the intestinal mucosa and disrupting the mucosal immune responses.
Excessive alcohol consumption can cause changes in the frontal and temporal lobes of the brain early in life, and can disrupt neural networks associated with learning, memory, psychomotor speed, attention, executive functioning, and impulsivity. In the intestines, alcohol alters the level of metabolites, increases inflammation, and disrupts the integrity of the intestinal epithelium.
Cannabis use increases the activity of cannabinoid receptors and results in a number of health outcomes, including gastric acid secretion, reduced intestinal motility, and intestinal permeability and induction of inflammation. In addition, research has shown that the initial use of cannabis is linked to a decline in cognitive abilities.
Regular sleep patterns can be affected by a number of factors, including shift work, night light exposure, inconsistent food intake time, healthy eating, and jet lag. A change in sleep time and pattern is commonly seen among adolescents, associated with mental disorders such as depression and anxiety.
A disruption of sleep patterns can also disrupt the homeostasis of the intestinal microbiome by increasing harmful microbes and reducing beneficial microbes and metabolites.
- Lee JE. 2022. Drugs, guts, brains, but not rock and roll: the role of the intestinal microbiota in contemporary mental health and well-being of adults that needs to be considered. International Journal of Molecular Sciences. https://www.mdpi.com/1422-0067/23/12/6643