In recent years, the gut microbiome has emerged as a focal point in nutrition and healthcare. It comprises an ecosystem of trillions of microorganisms, including bacteria, viruses, and fungi, that inhabit the digestive system and predominantly in the large intestines. The human adult gut contains over 1kg of microbes, essentially the same weight as the human brain.
The profound impact of the gut microbiome extends far beyond digestion, influencing immune regulation and the health of various organs through the gut-brain-body axis; the gut microbiota also appears to play a pivotal role in several health conditions.
Gut barrier function
The gut barrier is one of the body's primary defense systems, protecting the internal organs and systems from the external environment and invasion by pathogens (organisms that can produce diseases), allergens and toxins. The gut barrier comprises:
- A single-cell epithelial lining and a mucus layer are home to a vast community of microbes consisting of bacteria, fungi, and viruses that coexist in a natural balance—also known as the gut microbiome.
- A biochemical layer that provides enzymes and antimicrobial proteins to protect against invading microorganisms, toxins, and allergens.
- An immunological epithelial layer contains 70-80% of the body’s immune cells, which regulate immune response.
Immune system hotspot
The gut microbiome is intricately tied to the immune system. A disturbance in the natural balance of the gut microbes causes dysbiosis (imbalance in the gut microbiome associated with disease), thinning of the mucus layer, inflammation and loss of the natural protective barrier, resulting in a “leaky gut”. This process tends to cause the release of several microbial metabolites and endotoxins (toxins found in a bacterial cell), often resulting in an excessive immune response linked to several health conditions.
Digestive system symbiosis
The gut microbiome is a critical partner in the digestive process. It ferments and breaks down complex carbohydrates, processing them into nutrients our bodies can readily absorb. This collaborative effort ensures the absorption of essential vitamins, minerals and short-chain fatty acids.
However, the lifestyle factors below are linked to gut health and the development of dysbiosis and chronic low-grade inflammation.
- Processed foods, alcohol
- Change in gut pH
- Acute and chronic medication Injuries (especially neck, lower back and spinal injuries)
- Daily stress and poor sleep
- Hormone imbalance
- Thyroid dysfunction
- Allergens and toxins
The image below depicts the recurring pattern of inflammation.
Figure 1. An illustration of impact factors that tend to create dysbiosis and affect multiple organs and systems through the gut-brain-body axis.
The gut-brain-body axis
The gut and brain constantly communicate with each other and other organs in the body. This communication is regulated through various pathways, including direct contact with the central nervous system, enteroendocrine cells, immune cells, and microbial metabolites. These pathways control essential functions such as intestinal permeability (absorption), enteric reflexes, and immune activation.
The role of the vagus nerves
The vagus nerves are essential to the parasympathetic nervous system, regulating various bodily functions. They act as the main two-way communication channel linking the brain, gut, and blood supply to the body's interconnected systems.
The vagus nerves can sense changes in the gut environment, such as alterations to the microbial balance, and transmit this information to the central nervous system, generating an appropriate response.
The vagus nerve also releases a neurotransmitter called acetylcholine, which prevents the release of pro-inflammatory cytokines (proteins causing inflammation in the body), essential in reducing the inflammatory response and helping the body maintain a state of balance.
Loss of the gut's protective barrier disrupts the natural balance of physiological processes via the gut-brain axis. Research shows that this disruption affects metabolism and causes an imbalance of the immune response associated with numerous disorders and conditions.
Gut dysbiosis and inflammation often cause diarrhoea, food sensitivity, and reduced nutrient absorption due to changes in digestion and stool formation. Food allergies may also be involved.
Other associated health conditions include reflux, irritable bowel syndrome, and gastric ulcers due to changes in gut pH balance.
Stimulating the vagus nerve helps promote relaxation, also known as the "rest and digest" state. This helps alleviate inflammation, which is often associated with stress and anxiety. This process is referred to as the "vagus nerve anti-inflammatory reflex".
Dysbiosis is also linked to other neurological conditions, such as spectrum disorders and age-related neurological conditions.
Skin health and disorders
The skin has its natural microbial community. Disruption of the gut or skin barrier can cause skin inflammation, sensitivity, acne, slow wound healing, loss of elasticity and dehydration.
Dysbiosis and loss of the gut’s protective barrier contribute to inflammation linked to elevated cholesterol levels and hypertension.
Obesity and weight regulation
Gut microbial diversity may determine whether an individual is prone to weight gain. A balanced natural microbiome community has been shown to help maintain a healthy weight, while obesity is associated with imbalance.
Diabetes and insulin resistance
Dysbiosis is linked to insulin resistance, a critical factor in the development of type 2 diabetes.
The gut and liver are intricately connected. Microbial balance is essential for a healthy liver, while dysbiosis may contribute to various liver diseases, including non-alcoholic fatty liver disease (NAFLD).
Both genetic and environmental factors contribute to autoimmune conditions. Dysbiosis is identified as a contributor due to the associated chronic inflammatory process and flare-ups in these conditions.
Several autoimmune conditions are associated with dysbiosis. These include digestive disorders such as inflammatory bowel disease (including Crohn's disease and ulcerative colitis); skin conditions such as atopic dermatitis, rosacea, and psoriasis; musculoskeletal conditions like osteoarthritis, rheumatoid arthritis, and multiple sclerosis, and endocrine conditions such as type 1 diabetes, Hashimoto's thyroiditis, and Graves' disease.
Understanding the intricate network and mutual communication system illustrates the interdependence between the gut microbiome and human health. Ultimately, this interconnectedness between the gut, the central nervous system, and other distant organs and systems play a crucial role in overall health and well-being.
Encouraging patients to limit foods that impact the gut barrier and adopt plant-rich diets to boost the intake of the nutrients and phytochemicals that lower inflammation and help maintain gut barrier integrity is key.
Addressing stress, chronic medication use, hormone imbalance, neck and lower back pain and inflammation is also integral to improving and maintaining a balanced gut microbiome.
Health practitioners play a crucial role in educating individuals about nurturing their internal ecosystem, which lays the foundation for overall well-being.
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