Introduction
The microbiome consists of microorganisms that are both helpful and potentially harmful. Most are symbiotic (where both the human body and microbiota benefit) and some, in smaller numbers, are pathogenic (promoting disease). In a healthy body, pathogenic and symbiotic microbiota coexist without problems.Gut microbiota have a crucial immune function against pathogenic bacteria colonization inhibiting their growth, consuming available nutrients and/or producing bacteriocins,the antibacterial protein. Gut microbiota also prevent bacterial invasion by maintaining integrity of the intestinal epithelium.The gut microbiota has broad impacts, including effects on colonization, resistance to pathogens, maintaining the integrity of intestinal epithelium, metabolizing dietary and pharmaceutical compounds, controlling immune function, and even behavior through the gut–brain axis.
Gut brain axis:
The gut-brain axis (GBA) consists of bidirectional communication between the central and the enteric nervous system, linking emotional and cognitive centers of the brain with peripheral intestinal functions. Recent advances in research have described the importance of gut microbiota in influencing these interactions.
The gut-brain axis is the biochemical signaling that takes place between the gastrointestinal tract and the central nervous system.That term has been expanded to include the role of the gut flora in the interplay; the term "microbiome-gut-brain axis" is sometimes used to describe paradigms explicitly including the gut flora.Broadly defined, the gut-brain axis includes the central nervous system, neuroendocrine and neuroimmune systems including the hypothalamic pituitary adrenal axis (HPA axis), sympathetic and parasympathetic arms of the autonomic nervous system including the enteric nervous system, the vagus nerve, and the gut microbiota.
Bacteria are the largest and to date, best studied component and 99% of gut bacteria come from about 30 or 40 species. Up to 60% of the dry mass of feces is consist of bacteria.Over 99% of the bacteria in the gut are anaerobes, but in the cecum, aerobic bacteria reach high densities.It is estimated that the human gut microbiota have around a hundred times as many genes as there are in the human genome.
Gut bacteria directly stimulate afferent neurons of the enteric nervous system to send signals to the brain via the vagus nerve. Through these var asied mechanisms, gut microbes shape the architecture of sleep and stress reactivity of the hypothalamic-pituitary-
adrenal axis.
Gut bacteria have been linked to depression, anxiety and the regions of the brain that process emotions. These regions share brain circuitry that affects cardiovascular issues such as blood pressure. "People have co-evolved with environmental bacteria (that have) adapted over eons to being at home in human bodies.
Gut bacteria affect brain health, so changing your gut bacteria may improve your brain health. Probiotics are live bacteria that impart health benefits if eaten. However, not all probiotics are the same. Probiotics that affect the brain are often referred to as “Psychobiotics”.
Gut bacteria have been linked to several mental illnesses, and patients with various psychiatric disorders such as depression, bipolar disorder, schizophrenia, and autism have been found to have significant alterations in the composition of their gut microorganisms.
Example of Beneficial or good gut bacteria:
Most of the probiotic bacterial strains described belong to the species Bifidobacterium (adolescentis, animalis, bifidum, breve and longum) and Lactobacillus (acidophilus, brevis, casei, fermentum, gasseri, johnsonii, paracasei, plantarum, delbrueckii, rhamnosus, reuteri and salivarius).
A systematic review from 2016 examined the preclinical and small human trials that have been conducted with certain commercially available strains of probiotic bacteria and found that among those tested, Bifidobacterium and Lactobacillus genera (B. longum, B. breve, B. infantis, L. helveticus, L. rhamnosus, L. plantarum, and L. casei), had the most potential to be useful for certain central nervous system disorders.
Improving your diet can help boost your gut health and may be able to help with anxiety. Researchers have found that high quality diets including those containing more fiber, omega-3, and “good” bacteria called probiotics may be linked to a lower risk of anxiety, stress, and depression symptoms.
A troubled intestine can send signals to the brain, just as a troubled brain can send signals to the gut. Therefore, a person's stomach or intestinal distress can be the cause or the product of anxiety, stress, or depression. That's because the brain and the gastrointestinal (GI) system are intimately connected.
(2014) found that bacterium namely Bifidobacterium longum improve the cognitive function in healthy Balb/c mice. (Bravo et al.)
Scientists find that gut microbes can regulate the early development of neurons in ways that lead to lasting impacts on brain circuits and behaviours.They also find that under shorter timescales, gut microbes can regulate the production of biochemicals, , that actively stimulate neuronal activity.
Way to improve gut bacteria for mental health:
One way is by eating prebiotics: foods which directly provide sustenance to your gut bacteria, like fruit, vegetables, whole grains, and pulses. These contain fibre which is transformed into SCFAs (short chain fatty acids) like butyrate. So, increasing your intake will positively affect your health!
The study, in mice, found that gut bacteria partly by producing compounds such as short chain fatty acids affect the behavior of immune cells throughout the body, including immune cells in the brain that can damage brain tissue and exacerbate neurodegeneration in conditions such as Alzheimer's disease.
Gut bacteria reduce stress anxiety and depression:
Preliminary evidence shows that imbalances in gut microbiota can exert a powerful influence on the brain via the gut-brain axis in ways that affect anxiety. What's more, disturbances in neurotransmitters brain chemicals that send signals throughout the body may play a role in psychological conditions like anxiety.
Improving your diet can help boost your gut health and may be able to help with anxiety. Researchers have found that high quality diets including those containing more fiber, omega-3, and “good” bacteria called probiotics may be linked to a lower risk of anxiety, stress, and depression symptoms.
Our gut microbiome is related to our mental health:
It is now a common belief that gut microbiota communicates with the central nervous system through neural, endocrine, and immune routes, and thereby controls brain function. Studies have demonstrated a substantial role for the gut microbiota in the regulation of anxiety, mood, cognition, and pain.
Millions of nerves and neurons run between your gut and brain. Neurotransmitters and other chemicals produced in your gut also affect your brain. By altering the types of bacteria in your gut, it may be possible to improve your brain health.
Gut bacteria have been linked to several mental illnesses, and patients with various psychiatric disorders such as depression, bipolar disorder, schizophrenia, and autism have been found to have significant alterations in the composition of their gut microorganisms.
The best gut bacteria for anxiety:
Try a multi-strain Lactobacillus/Bifidobacterium blend, as those have been found to have the most positive effects on anxiety and stress. For the best health benefits, also support gut healing and beneficial bacteria with an anti-inflammatory diet.
Moreover, several recent works, including have also shown that gut microbiota play an important role not only in the development of brain function but also in the pathology of stress-related diseases and neurodevelopmental disorders.
The normal gut microbiota imparts specific function in host nutrient metabolism, xenobiotic and drug metabolism, maintenance of structural integrity of the gut mucosal barrier, immunomodulation, and protection against pathogens. Several factors play a role in shaping the normal gut microbiota.
Role of the gut microbiota on brain development:
The gut microbiome plays an essential role in various processes of brain development such as neurogenesis, myelination, microglial maturation, development and maintenance of blood-brain barrier integrity, development of HPA-axis, and HPA-axis stress response.
The principal effectors of the stress response are localized in the paraventricular nucleus (PVN) of the hypothalamus, the anterior lobe of the pituitary gland, and the adrenal gland. This collection of structures is commonly referred to as the hypothalamic-pituitary-adrenal (HPA) axis .
Altered Gut microbes drive brain disorders:
The altered gut microbiome can cause dysregulated immune activation, igniting systemic inflammation resulting in atypical brain development leading to symptoms associated with neurodevelopmental psychiatric disorders (Garay and McAllister, 2010; Han et al., 2021; J.; Lu and Claud, 2019).
Information compiled by:
Dr.Bhairavsinh Raol
