What Is the Gut-Brain Axis?
The gut-brain axis is the two-directional communication between the gastrointestinal tract and the central nervous system. The communication is mediated by neural, hormonal, immune, and blood factors. The network constitutes the central nervous system (CNS), autonomic nervous system (ANS), enteric nervous system (ENS), and hypothalamic pituitary adrenal (HPA) system. Gut microbiota is a diverse group of beneficial microbes that exist symbiotically in the gastrointestinal tract to aid digestion and other metabolic activities. Recent studies have found that gut microbes can communicate with the brain through different pathways and play a significant role in maintaining the health of the central nervous system.
How Do the Gut and Brain Communicate With Each Other?
The digested food from the stomach enters the small intestine. In the small intestine, finger-like projections called villi are present. They are covered by epithelial cells, which also contain enteroendocrine cells. These cells can connect with various nerves, including the vagus nerve. The vagus nerve can transmit information from the gut to the central nervous system. However, gut microbes can also interact with the gut-brain axis through various other routes.
Which Disorders Are Associated With Gut-Brain Communication?
The disorders associated with the gut-brain axis are known as disorders of gut-brain interaction or DGBI. These disorders are not found to have any underlying cause and are categorized based on the symptoms. Some of the disorders that come under DGBI are:
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Gastroparesis - It is also known as partial paralysis of the stomach. It is a condition where the stomach can't empty the food in a normal way. This can be caused due to diabetes, Parkinson's disease, viral infection, injury to the vagus nerve, antidepressants, etc. The symptoms of gastroparesis are nausea, vomiting, heartburn, abdominal pain, and so on. It is commonly associated with eating disorders. Gastroparesis is a long-lasting condition and cannot be treated, but therapeutic medications and surgery can manage the symptoms.
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Functional Dyspepsia (FD) - It is characterized by chronic indigestion, and symptoms include epigastric pain, acid reflux, and a bloated stomach. People who are at high risk for developing this disease are women, people with helicobacter pylori infection, smokers, and patients with eating disorders. Treatment depends on the causative factors. If the disorder is caused due to infection, then it is treated with antibiotics. If it persists, it can be treated by acid reduction, prokinetic agents (which help empty the stomach), and so on. Besides, acupuncture, diet modification, lifestyle changes, and other treatments have proven beneficial.
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Irritable Bowel Syndrome (IBS) - It is a long-term gastrointestinal tract condition with symptoms like bloating, diarrhea, constipation, flatulence, abdominal pain, and cramps. The exact cause of this disease is not known. But the factors that can predispose to this syndrome include infection, muscle contraction in the intestine, and problems in the nervous system. People with irrational bowel syndrome are advised to consume fiber-rich food and take supplementary fibers. Antidepressants are prescribed to patients suffering from anxiety and depression with this syndrome. Intake of probiotics along with lifestyle changes also can treat irritable bowel syndrome.
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Functional Constipation (FC) - It is a long-term problem involving infrequent and difficult defecation. Functional constipation does not have an exact cause; even a healthy person may have this condition. It is very common in children. Intake of probiotics and fiber-rich food can manage constipation. Drug therapies with stimulant laxatives and other lubricants can treat the condition. Other treatment methods include rectal irrigation and enemas (rectally administered fluids).
What Is the Effect of Gut Microbiota on Mental Health?
An imbalance between the natural flora of microbes in the gut has been linked with anxiety and depression. Also, the intake of probiotics has shown a reduction in anxiety and depressive symptoms. Gut microbes play a role in depression by regulating the production of neurotransmitters like serotonin, dopamine, and glutamate. In addition, studies have found the role of gut microbes in neurological disorders like Parkinson's disease, schizophrenia, autism, and Alzheimer's disease.
Recent studies showed that people with anxiety and eating disorders like anorexia and bulimia showed a different profile of gut microbes. Anorexia and bulimia are considered psychiatric conditions rather than digestive disorders.
How to Improve the Gut Microbiota?
There are many ways to improve the gut microbial profile, which in turn improves the health of the gut and brain. Following are some of the ways an individual can adopt to improve their gut microbiota:
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Take Probiotic Food and Supplements - Probiotic food intake can increase the number of good bacteria in the gut. Some of the food rich in probiotics are:
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Yogurt.
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Cottage cheese.
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Buttermilk.
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Fruits like watermelon, bananas, grapes, etc.
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Vegetables like broccoli, cabbage, cauliflower, etc.
2. Reduce the Intake of Sugar - High sugar intake, especially artificial sweeteners, can harm gut microbes.
3. Don’t Take Antibiotics Unnecessarily - Antibiotics kill or stop the growth of disease-causing bacteria. But unnecessary intake of antibiotics may kill good bacteria as well. It is advised to take antibiotics only with a doctor's prescription.
4. Try a Vegetarian Diet - People who follow a vegetarian diet have healthier microbial flora than people who follow a non-vegetarian diet. Eating plant-based food can have a positive impact on gut microbes.
5. Avoid Smoking - Smoking can decrease the number of good bacteria in the gut. Moreover, it is also a causative factor of irrational bowel syndrome (IBS).
6. Exercise Regularly - Studies have shown that athletes have a variety of good microbial flora in their gut compared to others. Regular exercise can improve gut health.
7. Reduce Stress - Stressing, even for a short period, can have an effect on good bacteria in the gut. However, stress can be managed by exercise, meditation, and getting good sleep.
Conclusion
Gut microbes have a great influence on the central nervous system. The complex network of microbes and chemicals communicates in the gut-brain axis through signaling. Recent studies have shown changes in gut microbiota can cause neurological diseases like Parkinson's disease, Alzheimer's disease, anxiety, depression, autism, and many more. Alteration in gut microbes is caused mainly due to unhealthy eating habits, lack of exercise, smoking, etc. These factors can increase the number of bad bacteria, which can affect the digestive and nervous systems. However, diet modification and adopting a healthy lifestyle can improve gut and brain health.
