When the intestinal flora is mentioned, it is meant the microorganisms that live in the digestive system and have various beneficial functions related to the digestion of the host organism.
Intestines have an area of 400-500 m², that is, slightly larger than half of a football field. There are 500 species of bacteria known in the intestinal flora, and they range in number from 1 to 10 quadrillion.
Bacteria make up most of the flora in the large intestine and 60% of the stool. The number of species living in the digestive tract is estimated to be between 300 and 1000, and the opinion of many experts is that it is around 500. However, 99% of them are likely to belong to 30-40 species. Yeast species are among the living things that make up the intestinal flora.
The relationship between the gut flora and humans is a symbiotic and mutualistic relationship, meaning it benefits both parties. Although humans can live without intestinal flora, the intestinal flora has beneficial functions such as converting unused substances into usable substances by fermentation, training the immune system, and inhibiting the growth of harmful organisms. However, some intestinal microorganisms can also cause disease.
There are no microorganisms in the upper stomach and small intestine. Most bacteria are found in the large intestine, and the activities of these bacteria make the large intestine the most metabolically active organ in the body. Bacteria in the small intestine are predominantly Gram-positive and those in the large intestine are predominantly Gram-negative. In the first part of the large intestine, carbohydrates are fermented, and then proteins and amino acids are broken down. Different species are found in different parts of the gut under the influence of pH, immune system and peristaltic movements.
In the cecum and ascending colon the pH is low and bacteria multiply rapidly, whereas in the descending colon with neutral pH they grow slowly. More than 99% of the bacteria in the intestines are anaerobic, but the concentration of aerobic bacteria is high in the cecum.
Types of microorganisms in the intestines
Not all types of bacteria in the gut are identified because some cannot be cultured. Although the number of bacterial species varies greatly from person to person, these numerical ratios are fairly constant for a given individual. Most bacteria belong to the genera Bacteroides, Clostridium, Fusobacterium, Eubacterium, Ruminococcus, Peptococcus, Peptostreptococcus and Bifidobacterium. Aerobes such as Escherichia and Lactobacillus are less abundant. Species belonging to the genus Bacteroides constitute 30% of the bacteria in the intestines. Yeast genera found in the intestinal flora include Candida and Saccharomyces.
Functions of microorganisms in the intestinal flora
Gut bacteria have several functions that are beneficial to humans. These include helping indigestible foods to be broken down and absorbed, promoting cell growth, suppressing the growth of harmful bacteria, and preventing the passage of toxic products from the intestines into the blood.
In addition, preventing the formation of inflammation in the intestinal mucosa, reducing the formation of skin diseases, creating a clearer body, strengthening the immune system of the person, eliminating the pathogenic microorganisms that will go to the liver and increasing its load, ensuring that the immune system only responds to pathogens and protecting against some diseases. among the tasks.
Carbohydrate fermentation and absorption
Without intestinal flora, the human body cannot digest and use some of the carbohydrates it eats, because the enzymes necessary for the digestion of polysaccharides are only found in some intestinal bacteria. It has been shown that rodents growing in a sterile environment and lacking intestinal flora have to eat 30% more to maintain the same weight compared to normal animals. Compounds that cannot be fully digested without the aid of bacteria include some carbohydrates (such as starch), oligosaccharides, sugars (such as lactose) and alcohols, intestinal mucosa and proteins of shed intestinal epithelial cells.
Bacteria convert the carbohydrates they ferment into short chain fatty acids (SCFA). These are used by host cells and constitute an important energy source for humans. In addition, these fatty acids increase the water absorption capacity of the intestine, reduce the number of some harmful bacteria and ensure the proliferation of both intestinal cells and beneficial bacteria.
SCFAs include acetic acid, propionic acid, and butyric acid. Organic acids such as lactic acid and gases are also formed as a result of fermentation. These organic acids are used by the body and used in energy production. Another fermentation that takes place in the intestine is proteolytic fermentation, which breaks down undigested proteins such as enzymes, dead host and bacterial cells, and collagen and elastin found in foods. As a result of this fermentation, SCFA and carcinogens are formed. There is evidence that bacteria increase the absorption and storage of lipids. Bacteria also produce vitamin K2 and allow it to be absorbed by the body. It also helps the body absorb calcium, magnesium and iron.
Effects of microorganisms in the intestines on the intestinal tissue
Another benefit of SCFA is that they increase the growth of intestinal epithelial cells and control their proliferation and development. In addition, they also promote the growth of lymph tissues near the intestine. A healthy intestinal flora prevents the formation of pathogenic bacteria, that is, bacteria that will cause disease.
Another important effect of the intestinal flora is to prevent species that may harm the host from settling in the intestines. Harmful bacteria, such as yeasts and Clostridium dificile, cannot compete with beneficial bacteria, so their numbers remain harmless. On the other hand, they easily cause infections when the intestinal flora is lost.
Beneficial bacteria compete with pathogenic microorganism species for their attachment points on the surface of the large intestine and food inside the intestine, preventing the growth of pathogenic species. Symbiotic bacteria in the gut are more adapted to this ecological environment. In addition, internal bacteria send chemical signals to the host, telling them how much food they need, and the host gives them only that amount of food. Therefore, pathogens cannot obtain enough nutrients to multiply.
Local bacteria also secrete bacteriocins; These substances, the amounts of which can be regulated by the host, kill harmful bacteria. Another effect of fermentation is that, due to the formation of fatty acids, it increases the acidity of the environment and prevents the proliferation of harmful organisms that are not resistant to it.
The effect of intestinal flora on the immune system
Intestinal bacteria act continuously on the host's immune system in the systemic and intestinal mucosa. Bacteria play a key role in both the early development and lifelong functioning of the immune system in the intestinal mucosa. They stimulate lymph tissues located near the intestinal mucosa, enabling them to produce antibodies against pathogens. The immune system does not touch the beneficial bacteria and fights against the harmful ones.
As soon as a baby is born, bacteria settle in his digestive tract. The first settling bacteria affect the immune system's response, enabling them to be identified as belonging to the host. Therefore, the first bacteria determine the intestinal flora content that will exist throughout the person's life. Therefore, the immune system of a normal born baby is stronger than a baby born by cesarean section. From Berlin Postam, Dr. Habil Jurgen Schulz determined that the intestinal flora is shaped according to the feeding of infants with breast milk, cow's milk or formula after birth.
Accordingly, the pH-value of the intestinal contents of breastfed children was between 3.5 and 5, while the pH-value of formula-fed children was 7 or slightly above. The digestive organs produce an average of 7–8 liters of secretion (enzymes, hormones, vitamins, acids and alkaline substances) per day. The most ideal enzyme release occurs when the pH-value is between 4.5 and 6.5. The main factor that ensures the formation of a healthy oral and intestinal flora in the baby is the first flora swallowed by the mother from the vagina during birth. However, once the baby is weaned, the bacterial mix in the gut often changes from selective (facultative) aerobes to obligate anaerobes. Some members of the intestinal flora, such as some Bacteroides species, change their surface antigens to make themselves look like host cells, thereby surviving the immune response. Some harmful bacteria also use this strategy. The bacteria act on a condition called oral tolerance, meaning they make people less sensitive to an antigen produced by oral or digestive bacteria. A healthy intestinal flora prevents allergies.
It has also been shown that bacteria prevent allergies, that is, the immune system from overreacting to harmless antigens. When the flora of infants and young children is examined, it has been seen that the probability of harmful species such as C. difficile and S. aureus in the intestinal flora of those who have allergies or develop allergies in later years is higher, and the numbers of Bacteroides and Bifidobacteria are lower. We can explain this observation as follows; Since bacteria train the immune system in infancy, if these bacteria are deficient in time, an undertrained immune system that develops as a result may overreact to antigens. However, flora disorder can be a result of allergies, not a cause.
Antibiotics adversely affect the intestinal flora
Reducing the number of bacteria with the use of broad-spectrum antibiotics affects the health of the host and its ability to digest food. Antibiotics damage the intestinal flora when taken to cure bacterial diseases or inadvertently ingesting antibiotic-fed animal meat. Antibiotics not only kill pathogenic bacteria, but also important bacteria in the gut. Due to the increased use of antibiotics, there is a serious deterioration in the intestinal flora. This situation facilitates the collapse of the immune system of the person and the formation of chronic diseases.
Antibiotics can cause diarrhea by irritating the intestines, affecting the intestinal flora, or allowing pathogenic bacteria to multiply. Sometimes they can even cause constipation. This is the underlying cause of the emergence of previously non-existent ailments as a result of the use of antibiotics.
In addition, the foods we have taken for years are deposited in our intestines. Toxic substances accumulating here disrupt our intestinal flora, causing it to become unable to function normally.
Regulation of intestinal flora and detoxification
In the light of all this information, we can definitely say that keeping the intestinal flora within the accepted normal limits by rearranging is the indispensable rule of a healthy life. For this reason, every person who has reached the age of 35 should have a comprehensive stool analysis once a year and see the state of the intestinal flora. Colon hydrotherapy is the most effective treatment method that regulates the intestinal flora and purifies it from toxins. The intake of beneficial bacteria, namely probiotic supplements, through food is beneficial in terms of avoiding the negative effects of flora disorder and helping to restore the normal balance. From this point of view, probiotics are very important. Also called prebiotic,
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