Immune system - Microbiota (part 2)

Microbiota or microbiome is a group of microorganisms living in a given environment, creating their own ecosystem. It is the center from which a wide range of processes taking place in our body are managed. Although bacteria are found in the human body in many parts of the body, the most important role is attributed to the bacterial microflora of the intestines. Many people do not realize that about 2 kg of bacteria living in about six meters of the intestines have such a significant impact on our body. Bacteria perform many important functions, and disruptions to the flora can have many harmful effects on health.

Intestines – home to bacteria

It is currently assumed that there are from 106 to 1012 bacterial cells in 1g of content in the intestines ^.  This ^is a very large amount, totaling about 100 trillion . To put it simply, there is mucus in the intestines, which creates a living environment for bacteria. Some of the ingredients we consume are also a nutrient for bacteria, so the right environment and food enable the proper functioning of microflora. The entire natural process of microflora formation begins in the mother's womb. Then the child takes over the bacteria from her, and after birth they are joined by microorganisms from the environment. However, these are not permanent colonies - the not yet formed environment prevents significant growth. In the following days of life, the probiotic strains of Bifidobacterium and Lactobacillus dominate , for which mother's milk is good food. With age, the number of species and genera increases, while in old age it decreases.

Probiotic, prebiotic, synbiotic

These are three frequently confused concepts, sometimes appearing in advertisements for medicinal products and dietary supplements. First, it is necessary to define what probiotic bacteria are - these are specific species that have a beneficial effect on the human body (and this is scientifically proven), are able to survive in the human body and are naturally found in it.

A probiotic is a preparation that contains appropriate probiotic strains in appropriate amounts (108-109 ^cells / ml ).

A prebiotic is a preparation or substance that is a food for bacteria. For most microorganisms in the intestines, the main food is saccharides, both those absorbed by the body (e.g. glucose) and dietary fiber (otherwise, fiber, a fraction of saccharides not digested by the body, which is the main food for bacteria). Examples of prebiotics are inulin, fructooligosaccharides, pectins.

Synbiotic is a combination of probiotic and prebiotic, or an all-in-one preparation. It contains both microorganisms and a ready-made medium for them.

The influence of microflora on immunity

It is obvious that humans come into contact not only with beneficial bacteria, but also with harmful and pathogenic bacteria, which enter our bodies from the environment from the first days of life. Different pathogenic bacteria cause different diseases and ailments, so they cannot be described in a simple way. However, this is not so important - probiotic bacteria constitute the majority of intestinal microflora, and due to their biodiversity* they are able to fight various harmful species. Lactic acid bacteria, which constitute the largest part of intestinal microflora, have or produce quite a large arsenal to fight pathogens, including:

• Hydrogen peroxide – a substance with bactericidal properties, commonly known as hydrogen peroxide
• Organic acids – acidic environment does not support the growth of some bacteria
• Bacteriocins – bacteriostatic and antibacterial substances that disrupt the growth of bacteria
• Protease inhibitors – substances that inhibit the growth of harmful fungi

In addition, some studies indicate that bacteria affect the differentiation and expression of T lymphocytes; they may also affect the production of cytokines (proteins that stimulate immune activities).

Gut bacteria and the brain

There are about 100 million nerve cells in the intestines and their surroundings. This is a large number, comparable to those in the spinal cord. Communication between the intestines and the brain occurs through the ENS nervous system, it is assumed that 90% of all signals are those sent from the intestines, while a small part is sent in the other direction (i.e. from the brain). Bacteria in the intestines produce various types of neurotransmitters, including: GABA, noradrenaline, acetylcholine, dopamine, serotonin, melatonin. They affect our well-being, mood, and brain function. Some studies indicate that defects in microflora are associated with depression, and some strains of bacteria may have antidepressant effects (perhaps this is related to neurotransmitters). A 2011 study found that the Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 strains in the study group lowered the level of cortisol (stress hormone) and also reduced the occurrence of anxiety and depression.

Taking care of microflora, using probiotics

The first rule that we should apply not only to taking care of bacteria, but also to all organs of the body is to "do no harm". The first harmful things are of course antibiotics, or bactericidal drugs. They are used to cure a given disease, but they are not intelligent substances - they do not act selectively, but attack all bacteria, including the good ones. Therefore, they should be treated as a last resort when other treatment options do not bring results, and when this happens, the use of probiotics during and after antibiotic therapy is almost necessary. It is also worth paying attention to nutrition - ensure an adequate supply of fiber, avoid fasting (which negatively affects not only the microflora but the general condition of the intestines).

The use of probiotics as medicines or supplements is not necessary in preventive actions. If we take care of the general condition of the intestines and we are not sick, or the intestines are not sterile, then standard support is enough, i.e. appropriate nutrition including fermented products. Probiotics can be used in special conditions, i.e. diseases and in accordance with the doctor's recommendations.

“Probiotic” Foods

This term simply means products containing probiotic bacteria, or to simplify it even more, fermented food. Consuming such products supports intestinal microflora: we then provide both prebiotics and the bacteria themselves, which are found in fermented food. Considering the above benefits and low calories, a large amount of vitamins, easy preparation, low price, these are very good components of the diet. Selected examples of products from this group:

• Sourdough bread
• Pickles: cabbage, cucumbers, onions, beets, mushrooms
• Cheeses: mozzarella, cottage cheese
• Buttermilk, kefir, yogurts
• Fermented juices, kvass
• Kombucha

There are many more products of this type, and interestingly, pickled vegetables can be made from most vegetables available in Poland.

In summary, bacteria are with humans already in the mother's womb and accompany them throughout their lives. We have contact with both useful and harmful ones, but Mother Nature has planned everything so that our little friends provide us with health and proper functioning. Human microflora has many functions and it is worth taking care of it to avoid health problems.

*Biodiversity – multi-species microflora, which means that different species of bacteria live in the human body, and each of them counteracts harmful bacteria to a different extent. For example, species A will have a weak effect against pathogenic species B, but species X also lives in the intestines and effectively eliminates harmful species B.