How Do Microbes Contribute to Our Health

For more than a hundred years it was believed that microbes are nothing but the causative agents of various diseases. Only recently it was discovered that trillions of microorganisms living on us and in us are more useful than harmful to our organism.

Key takeaways:
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    Trillions of microorganisms coexisting in/on different sites of the human body (skin, gut, lung, vagina, oral and nasal cavities) are called microbiota.
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    Among different sites microbiotas, the intestinal microbiota plays a key role in maintaining healthy organism.
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    Gut microbiota dysbiosis may initiate the development of various diseases in the organism.
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    Live microorganisms found in fermented food products (fermented milk, yogurt, fermented vegetables, etc.) and artificially produced food supplements are called probiotics.
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    Probiotics may help to improve host gut microflora, its resistance against infections, properly modulate person’s immune system responses, and even suspend/stop the progression of diseases.

So how do these microbes contribute to our health and disease?

Microorganisms and health

Bacteria, yeasts, viruses, fungi and microalgae are microorganisms (aka microbes) which exist everywhere on planet Earth. They are not only essential to our planet, but can also demonstrate a profound impact on human health.

A set of microbes that help to maintain stable organism conditions (aka homeostasis) and benefit its health are called microbiota. The term “microbiota” is known since the early 1900s when it was discovered that various microorganisms resided in/on different sites of the human body (skin, gut, lung, vagina, oral and nasal cavities ). Numerous scientific studies have shown that the composition of microbiota varies from site to site and the microbes found in the gastrointestinal tract are the most significant ones in maintaining healthy organisms.

Gut microorganisms can benefit human health by several mechanisms. First of all, due to unique enzymes (undetectable in human cells) microbes assist in food digestion. This helps to extract extra energy and nutrients from food. Secondly, they protect against pathogens by producing antimicrobial substances and synthesizing intestinal mucosa (the inner lining of the intestinal tract, which prevents uncontrolled translocation of pro-inflammatory molecules, such as microorganisms, toxins, and antigens, into the body). Finally, microorganisms produce bioactive molecules (vitamins, amino acids, and lipids) beneficial for human organisms.

Microorganisms and disease

Current advances in science have shown that there is a relationship between human microbiota and diseases, where the most important player again is gut microbiota. In healthy conditions, the gut microbiota demonstrates coexistence, stability, and symbiotic interaction with the host. Meanwhile, the changes in microbiota composition (microbiota dysbiosis) may initiate the development of various diseases in the organism.

Many factors may trigger gut microbiota changes. Some of them are dependent on human behavior (dietary habits, lifestyle, etc.), while others are independent (genetics, birth method, etc.). Even though it is believed that manipulation of microbiota composition in the human body can be a key to disease treatment, the human-dependent factors are the ones that can be utilized to restore imbalanced microbiota.

Numerous of large-scale microbiome studies have been performed in recent years, but the exact mechanism of how gut microbiota induces disease formation has not been completely elucidated yet. However, it is hypothesized that microbiota metabolites (microorganisms synthesized bioactive molecules) play a key role in gut homeostasis maintenance and disease formation. The table below depicts the main diseases which according to scientific studies may be a consequence of gut microbiota dysbiosis.

Disease categoryDisease name
NeurodegenerativeAlzheimer disease.
Parkinson disease.
CardiovascularAtherosclerosis.
Hypertension.
MetabolicObesity.
Diabetes.
Non-alcoholic fatty liver disease.
GastrointestinalInflammatory bowel disease.
CancerParticularly abdominal cancers (e.g., colorectal cancer, etc.)
AutoimmuneSystemic lupus erythematosus.
Spondyloarthritis.
Rheumatoid arthritis.

Microorganisms for diseases treatment

Probiotics are live microorganisms that confer health benefits to a person. Properly dosed probiotics help to improve host gut microflora, and its colonization resistance against infections, properly modulate a person's immune system responses, and even slow down/stop the progression of diseases.

Probiotics can be found in various fermented food products (fermented milk, yogurt, fermented vegetables, etc.) and artificially produced food supplements. Many different microbes are utilized in the production of food supplements. Among them, the most commonly used are Bifidobacterium and Lactobacillus species, and a species of yeast (Saccharomyces boulardii). As more is learned about the bacteria that reside in the healthy human body, the range of species used as probiotics rapidly expands.

When choosing probiotics as diet supplements, it is important to pay attention to their label. They should include the detailed health benefit, proper dosage, storage conditions, and colony-forming units (CFU; the number of alive/active microorganisms in one serving of a probiotic supplement). It is very important, that microorganisms must be alive when administrated.

The public believes that probiotics positively impact the gut microbiome. However, this belief in turn can not be fully supported by the scientific research data, as studies demonstrate only the subtle impact of probiotics on the gut microbiota. Still, it does not mean that probiotics have no effect, their impact may be limited to minor microbiota components (e.g. metabolites) which cannot be detected by the current scientific techniques.

Microbes residing on and in our bodies are extremely important in maintaining the balance of organisms. Following the principles of a healthy lifestyle, we can help our microbiota to remain stable and in symbiosis with our body. The sustainment of such a state can help to prevent the onset and development of many diseases.

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