The gut microbiota is a complex ecosystem of microorganisms, including bacteria, viruses, fungi, and parasites, that inhabit the human gastrointestinal tract. The number of microbes in the human body is about 39 trillion, slightly exceeding the number of our own cells. However, their genetic material is significantly richer and has a profound impact on bodily functions.
The microbiota performs many key functions such as aiding in digestion, synthesizing vitamins, protecting against pathogens, and supporting the immune system. A healthy microbiota is key to long-term health maintenance, while its disturbances can trigger a multitude of diseases.
How Does the Microbiota Affect Our Body?
The gut microbiota plays a crucial role in regulating metabolism, maintaining healthy weight, and preventing metabolic disorders. Its imbalance can lead to the development of obesity, insulin resistance, and chronic inflammation.
- Weight regulation: Akkermansia muciniphila and Faecalibacterium prausnitzii are associated with maintaining a healthy metabolism and preventing obesity. An imbalance in the microbiota can lead to increased calorie absorption and the development of insulin resistance, which contributes to weight gain.
- Production of SCFAs (short-chain fatty acids): The microbiota ferments dietary fibres, producing butyrate, acetate, and propionate, which improve insulin sensitivity, reduce inflammation, and support the health of the gut barrier.
Hormonal Balance and Gut Microbiota
The gut microbiota influences hormonal balance by regulating estrogen metabolism and stress hormone levels. Disruptions in the microbiota can exacerbate hormonal imbalances and contribute to the development of inflammation.
- Estrogen: The microbiota regulates estrogen levels, including the dominance of estrogen, which can affect the risk of endometriosis, polycystic ovary syndrome (PCOS), and breast cancer.
- Cortisol: Stress and microbiota imbalance affect the hypothalamic-pituitary-adrenal axis, enhancing chronic stress and impairing immune function.
Maintaining Body Barriers
The gut microbiota plays a key role in maintaining the body’s protective barriers, and safeguarding mucosal linings and skin.
- Gut barrier: The microbiota helps maintain intestinal integrity, preventing the penetration of pathogens. Damage to this barrier, known as “leaky gut,” is associated with systemic inflammatory responses, autoimmune diseases, and allergies.
- Skin barrier: Disruptions in the microbiota can affect skin health, causing conditions such as acne, eczema, psoriasis, or rosacea.
Detoxification and Protection Against Toxins
The gut microbiota participates in detoxification, helping to metabolize toxins and produce protective substances.
- Toxin metabolism: Gut bacteria help neutralize toxins, reducing the load on the liver.
- Bioactive substances: The microbiota transforms food into beneficial metabolites, supporting cell health and reducing inflammation.
Impact on the Cardiovascular System
The microbiota affects the cardiovascular system by regulating inflammation and metabolism.
- Trimethylamine-N-oxide (TMAO): A byproduct of microbiota metabolism that can increase the risk of heart disease.
- Reduction of Inflammation: Short-chain fatty acids produced by the microbiota help reduce inflammation and improve heart health, decreasing the risk of developing atherosclerosis, hypertension, and other cardiovascular diseases.
Energy Metabolism
The gut microbiota facilitates efficient energy metabolism, which is important for overall energy levels and fatigue.
- Nutrient Absorption: The microbiota aids in the digestion of nutrients, improving energy access and preventing chronic fatigue.
Emotional Health and the Gut-Brain Axis
The microbiota plays a significant role in regulating emotional state and cognitive functions through its influence on neurotransmitters and neuroinflammation.
- Neurotransmitter Production: The microbiota is involved in the synthesis of serotonin (up to 90% of which is produced in the gut), GABA, dopamine, and other neurotransmitters that affect mood and cognitive functions. Changes in the microbiota are linked to the development of depression, anxiety, autism, and dementia.
- Neuroinflammation: An imbalance in the microbiota can enhance inflammatory processes in the brain, affecting memory and mood.
The Connection Between Gut Flora and Fertility
Normal function of the microbiota is critically important for reproductive health, affecting the absorption of fats and the synthesis of hormones.
- Sex Hormone Synthesis: Fats are necessary for hormone production; their deficiency can reduce fertility. Therefore, their absorption in the gut is extremely important for fertility.
- Impact of Fats: The microbiota also helps absorb and/or produce fat-soluble vitamins (A, D, E, K), which are necessary for reproductive health:
- Vitamin A: Regulates the maturation of oocytes and the health of reproductive tissues.
- Vitamin D: Maintains normal ovarian function and sperm quality.
- Vitamin E: Protects reproductive system cells from oxidative stress.
- Vitamin K: Ensures normal blood circulation, important for embryo implantation.
What is Dysbiosis?
Dysbiosis is a condition that disrupts the balance between beneficial (“good”) and harmful (“bad”) microorganisms in the gut, also known as a microbiota imbalance. In a healthy state, the microbiota consists of a diverse array of bacteria working together to maintain the body’s harmonious function. However, various factors such as unbalanced diet, antibiotic use, stress, and chronic diseases can alter this balance. Changes in the composition of the microbiota can lead to numerous health problems:
- Excessive growth of pathogenic microorganisms: An increase in pathogens creates conditions for their active reproduction and survival in the gut.
- Formation of pathological biofilms: Pathogens create protective biofilms that shield them from the immune system and antimicrobial therapy, enhancing their resistance.
- Reduction in the number of beneficial bacteria: The loss of beneficial microorganisms leads to a decrease in their protective functions in the gut and reduces its barrier function.
- Disruption of gut barrier integrity (“leaky gut”): Increased permeability of the mucosal lining allows toxins, allergens, and inflammatory molecules to enter the bloodstream.
- Excessive bacterial growth in the small intestine (SIBO): Characterized by an increase in bacteria in areas where they are usually scarce, which can cause bloating, diarrhea, and other digestive problems.
Dysbiosis is associated with the development of numerous diseases, including inflammatory bowel diseases, metabolic disorders, allergies, autoimmune diseases, and even depression.
Types of Dysbiosis
It can affect both the large and small intestine, leading to various health problems but with relatively similar symptoms.
Dysbiosis of the Large Intestine
- Bloating: Gas production resulting from the fermentation of undigested carbohydrates.
- Abdominal pain: Irritation of the intestinal wall due to excessive growth of pathogenic microorganisms.
- Constipation or diarrhea: Disruption of beneficial bacteria responsible for breaking down dietary fibres can cause either stool retention or excessive stool liquefaction.
Primary Causes of Large Intestine Dysbiosis:
- Antibiotics: Destroy both harmful and beneficial bacteria, disrupting the balance of the microbiota.
- Improper Diet: Excessive consumption of sugar, lack of fibre, and a lack of diverse foods can reduce the diversity of the microbiota.
- Stress: Affects the “gut-brain axis,” reducing the intestinal barrier function and promoting dysbiosis.
- Chronic Diseases: Certain diseases, such as diabetes, celiac disease, or inflammatory bowel diseases (such as Crohn’s disease or ulcerative colitis), can impact the gut microbiota.
- Use of Other Medications: Contraceptive pills, anti-inflammatory drugs, and steroids can alter the microbial balance in the gut.
- Lifestyle Changes: A lack of physical activity, excessive alcohol consumption, smoking, and other toxins can also affect the composition of the microbiota.
- Age-related Changes: As one age, the composition of the microbiota naturally changes, which can contribute to the development of dysbiosis.
- Infections: Intestinal infections caused by pathogenic bacteria, viruses, or parasites can temporarily disrupt the balance of gut flora.
Dysbiosis of the Small Intestine (SIBO/SIFO) Key Manifestations:
- Bloating After Eating: A result of active food fermentation when bacteria typical of the large intestine start proliferating in the small intestine.
- Impaired Nutrient Absorption: Bacterial proliferation in the small intestine hinders the normal process of vitamin and mineral absorption.
- Constipation or Diarrhea: An imbalance in the microflora can lead to changes in stool consistency.
Primary Causes of Small Intestine Dysbiosis:
- Gut Motility Disorders: Include slowed peristalsis due to diabetes, changes in sex hormone levels or hypothyroidism, nervous system dysfunction, improper functioning of valves, age-related changes, chronic constipation, and consequences of food poisoning.
- Disorders in the Composition and Activity of Gastric Juice: Lack of stomach acid and digestive enzymes.
- Anatomical Changes: Post-surgical changes and obstruction of the intestinal lumen by adhesions or scars.
- Immune Disorders: Immunodeficiency and impaired barrier function of the intestine.
- Microbiota Disorders: Use of antibiotics, excessive consumption of carbohydrates, and dysbiosis.
- Hormonal Changes: Hypothyroidism, diabetes, and changes in sex hormone levels.
- External Factors: Chronic stress, a diet high in sugar and processed carbohydrates, low fibre intake.
To learn more about small intestinal bacterial overgrowth (SIBO) and its impact, read the articles:
- SIBO: What Lies Behind the Condition Mistaken for a Disease, Part 1
- SIBO: What Lies Behind the Condition Mistaken for a Disease, Part 2
Conclusion
In this article, we examined the role of gut microbiota in maintaining human health, its impact on metabolism, hormonal balance, the body’s barrier functions, detoxification, and its influence on the cardiovascular system. We also discussed how an imbalance in the microbiota, known as dysbiosis, can lead to various diseases and disorders, including inflammatory and autoimmune conditions, metabolic disturbances, and even mental health issues.
In the second part of this article, we will explore methods for diagnosing and treating dysbiosis, providing readers with insights on how to manage microbiota health to support gut well-being.