What Is Gut Flora?

Intestinal flora, normal microorganisms of the human intestine, such as bifidobacteria, lactobacillus, etc., can synthesize a variety of vitamins necessary for human growth and development, such as B vitamins (vitamins B1, B2, B6, B12), vitamin K, smoke Acid, pantothenic acid, etc., can also use protein residues to synthesize essential amino acids such as aspartic acid, phenylalanine, valine and threonine, and participate in the metabolism of sugars and proteins, while also promoting iron, Absorption of mineral elements such as magnesium and zinc. These nutrients have important effects on human health, and lack of them can cause many diseases.

Intestinal flora, normal microorganisms of the human intestinal tract, such as bifidobacteria, lactobacillus, etc. can synthesize a variety of vitamins necessary for human growth and development, such as B vitamins (vitamins B1, B2, B6, B12), vitamin K, smoke Acid, pantothenic acid, etc., can also use protein residues to synthesize essential amino acids such as aspartic acid, phenylalanine, valine and threonine, and participate in the metabolism of sugars and proteins, while also promoting iron, Absorption of mineral elements such as magnesium and zinc. These nutrients have important effects on human health, and lack of them can cause many diseases.

There are 10 trillion bacteria parasitic in the human intestine, which can affect weight and digestive ability, protect against the risk of infection and autoimmune diseases, and control the body's response to cancer treatment drugs. ^[1]

Chinese scientific name: Intestinal flora
Physiological function: Absorbs water, softer stool

Helpful: Vitamin Synthesis
Distribution: There are more than 400 bacteria in the colon

Intestinal flora bacteria classification

^[2] Classified according to the number of culturable bacteria. In the intestinal flora, there can be more than 400 species of bacteria that can be cultivated. According to their number, they can be divided into primary (dominant) flora (predominant microflora) and secondary flora ( sub-dominant microflora).

The main (dominant) flora: refers to bacteria with a large number or intensive population in the intestinal flora, generally above 10-10 cfu / g, including Bacteroides, Eubacteria, Bifidobacteria, Rumenococcus Obligate anaerobic bacteria such as Clostridium and usually belong to the native flora. The dominant flora is a flora that exerts physiological functions on the host, which greatly affects the function of the entire flora, and determines the physiological and pathological significance of the flora to the host.

Secondary flora: the quantity is below 10 ~ 10cfu / g, mainly aerobic or facultative anaerobic bacteria, such as E. coli and streptococcus, etc., which are highly fluid and potentially pathogenic, most of which are foreign bacteria Swarm or passing flora.

Lactobacillus is classified as a minor flora in quantity and is relatively high in the ileum, but it has more important functions, so it belongs to the dominant flora functionally.

The dominant flora is closely related to the characteristics of the micro-habitat. The dominant flora, mainly anaerobic bacteria, generally lives in micro-habitat with low clearance rate and rich nutrition, such as the colon, so the flora density and diversity are high; and Facultative or aerobic flora generally lives in microhabitats with high clearance rates, such as the proximal small intestine, and its flora density and flora diversity are low. Due to the low flora density, it is difficult to be called an "advantage "Bacteria"; in acidic microhabitats, acid-resistant and acid-producing bacteria become the dominant flora. Changes in the microhabitat can replace the dominant flora in the flora. For example, the dominant flora in the stool during constipation is mainly Gram-negative anaerobic bacteria, and Gram-positive bacteria are common in chronic diarrhea. The predominant flora in the stool during diarrhea is pathogenic bacteria or some facultative / aerobic bacteria. In the intestine, although obligate anaerobic bacteria are the main flora and dominate, these flora depend on the existence of secondary flora such as aerobic or facultative anaerobes, because the latter is consumed during the proliferation process Oxygen guarantees the growth conditions of the former. A physiological combination of intestinal flora is beneficial, while a pathological combination of intestinal flora is harmful.

Of the microorganisms in the human intestine, more than 99% are bacteria, and there are about 100 trillion living species, with 500 to 1,000 different species. These huge numbers of bacteria can be roughly divided into three major groups: beneficial bacteria, harmful bacteria and neutral bacteria.

Beneficial bacteria, also called probiotics, are mainly various types of bifidobacteria and lactobacillus. They are indispensable elements of human health. They can synthesize various vitamins, participate in food digestion, promote intestinal peristalsis, and inhibit pathogenic bacteria. Swarm growth, decomposition of harmful and toxic substances.

Harmful bacteria, once the quantity grows out of control, will cause a variety of diseases, produce harmful substances such as carcinogens, or affect the function of the immune system.

Neutral bacteria, that is, bacteria with dual effects, such as E. coli and Enterococcus, are beneficial to health under normal conditions. Once the proliferation is out of control, or it is transferred from the intestine to other parts of the body, it may cause many problems.

Human health is closely related to the structure of the probiotic flora in the intestine. In the long-term evolution of the intestinal flora, through individual adaptation and natural selection, between different species in the flora, between the flora and the host, between the flora, the host and the environment, there is always a dynamic equilibrium state. Form a system of interdependence and mutual restraint, therefore, under normal circumstances, the human body's flora structure is relatively stable, and it appears to be non-pathogenic to the host.

Some studies have pointed out that the proportion of beneficial bacteria in the intestine of strong people reaches 70%, that of ordinary people is 25%, that of constipated people is reduced to 15%, and the proportion of probiotics in the intestine of cancer patients is only 10%.

Intestinal flora

Physiological functions of beneficial bacteria flora:

If the intestinal beneficial flora is dominant, the intestinal mucosa is pink, indicating that the intestinal environment is quite good.

1. Absorb moisture, softer feces and easier excretion

Foods that are partially digested in the stomach are absorbed through the small intestine, and then become viscous and sent to the large intestine. After 18 hours, it absorbs water and minerals and turns into easily excreted feces. When the intestinal environment is good, the softness and hardness of the stool are moderate, and the bowel movement will be smooth.

2. Mild peristalsis, can excrete feces smoothly

With the peristalsis of the intestine, the feces are slowly pushed to the anus. If the peristalsis is too fast or too slow, it will affect the composition of the stool, causing constipation or diarrhea. If the intestines are clean, the speed of peristalsis is quite regular, and the feces can be smoothly discharged.

3.It helps vitamin synthesis

Good bacteria such as Bifidobacterium can maintain the health of the skin, and have the functions of synthesizing vitamins B1, B2, and B6 that help to generate heat, and vitamin K related to hemostasis and bone formation. In healthy intestines, good bacteria will continue to multiply, and vitamin synthesis will proceed smoothly.

4. Quickly discharge harmful substances

A healthy intestine is not completely free of bad bacteria, and harmful substances will be produced to some extent. Of course, it also includes food chemical additives that are eaten into the body or substances that cannot become nutritional ingredients. As long as the intestinal environment is good, these substances are excreted before they begin to harm the body.

5.Avoid pathogenic bacteria

Good bacteria such as Bifidobacterium can stimulate and improve the body's immune function, and are prone to cause food poisoning and other pathogenic bacteria. Because of their fear of acid, lactic acid drinks or healthy foods that contain good bacteria can inhibit pathogenic bacteria in the intestine Within breeding.

In addition to the above functions, the intestinal beneficial bacteria flora also has nutritional effects on the human body, such as diabetes, hypertension, and hyperlipidemia. B vitamins and non-essential amino acids have an important effect on human hair. When these nutrients are lacking, it can cause hair loss, yellowing, split ends, and easy breakage.

Physiological functions of harmful bacteria flora:

If the harmful bacteria flora "victory", the intestinal mucosa is rough, and the blood is dark and red.

1. Excretion is not smooth, and feces are accumulated in the intestine

In order to help defecation, the softness and hardness of the feces should be moderate, but the unhealthy intestines can cause the large intestine to accumulate due to the lack of dietary fiber, or the bacterial infection caused by the reproduction of bad bacteria, which will cause diarrhea.

2. Creeping too fast or too slow

Unhealthy intestines may affect the peristalsis of the intestines too quickly or too slowly, preventing smooth excretion of feces. As a result, the stool will become too hard or too thin, which will eventually lead to constipation, and the intestinal bacteria in the intestinal tract will multiply faster, so the vicious cycle continues.

3.Producing harmful substances

An unhealthy intestine is an excellent place for bad bacteria to multiply, and a large number of bad bacteria can cause harmful substances such as ammonium, sulfide and skatole. These substances are not only the source of malodorous farts, but also accelerate the aging of the intestinal wall, produce substances that cause cancer, and become the root cause of colorectal cancer.

4.Re-absorb substances harmful to the body

Harmful substances will not stay in the intestine obediently, it will circulate with the blood as the intestines absorb it, causing tiredness, dry skin, headache, vomiting and other physical discomfort, and substances that cause odor will pass through the blood and pass through the mouth Or the body.

5, pathogens easily invade

In an unhealthy intestine, the amount of good bacteria such as lactic acid bacteria will decrease, and the intestine will become alkaline. In addition, harmful substances produced by bad bacteria reduce the immune function of the intestinal wall, resulting in weakened intestinal bactericidal effect, and bacteria or pathogenic bacteria are more likely to invade.

Ecological balance of intestinal flora

The dynamic balance between humans and microorganisms is called microecological balance, and the factors affecting its microecological balance include external environmental factors and host factors. The external environment is mainly produced by changing the host's physiological functions, such as beneficial bacterial flora, through the production of bacteriocins, antibiotics and their metabolites, and competition for nutrition, space for the prevention of the invasion of passing bacteria and maintenance of their own stability. When the ecology is balanced, it can maintain the normal physiological functions of the host, such as nutrition, immunity, and digestion. Ecological disorders can be caused by chronic diseases, cancer, surgery, radiation infections, and inappropriate use of antibiotics.

For those who have intestinal microecological imbalances, they can eat more alkaline foods containing dietary fiber. They can also be supplemented with microecological preparations such as ecological live bacteriocin, bifidobacteria, or stachyose to better regulate the intestinal microecological health. .

Intestinal flora distribution

A variety of microorganisms reside in the gastrointestinal tract of healthy people. These microorganisms are called intestinal flora. Bacteria in the human gastrointestinal tract can constitute a huge and complex ecosystem, with more than 400 species of bacteria in a human colon. ^[3]

Most of the bacteria that enter the stomach from the mouth are killed by gastric acid, and the rest are mainly Gram-positive aerobic bacteria. The concentration of bacteria in the stomach is <10 3 CFU / ML (CFU is colony forming unit).

The composition of the intestinal flora is between the stomach and the colon. The flora of the proximal small intestine is similar to that in the stomach, but E. coli and anaerobic bacteria can often be isolated. In the distal ileum, between anaerobic.

The flora of the proximal small intestine is similar to that in the stomach, but E. coli and anaerobic bacteria can often be isolated.

In the distal ileum, the number of anaerobic bacteria began to exceed that of aerobic bacteria. Among them, E. coli is constantly present, and anaerobic bacteria such as Bacteroides, Bifidobacterium, and Clostridium have a considerable number.

On the far side of the ileocecal valve, the bacterial concentration rose sharply, and the colon bacterial concentration was as high as 10.11 to 10.12 CFU / ml, and the total bacteria accounted for almost one-third of the dry weight of feces. Among them, anaerobic bacteria reached 10.3 to 10.4 times of aerobic bacteria. The main strains are Faecalis, Bifidobacterium and Eubacteria.

Influencing factors of intestinal flora

There are four main factors affecting the intestinal flora: the human body's own factors (the acidity and alkalinity of the intestine, the secretion of bile and digestive enzymes, the peristalsis of the intestine, the secretion of intestinal mucus, the detachment of the intestinal epidermis, etc.) And human environmental factors (stress, business trips, etc.); human diet (digestible food and indigestible fiber, drugs, etc.); bacterial factors (bacterial adhesion, reproduction ability, nutritional requirements, etc.) Anti-digestive enzyme capacity, etc.); interactions between bacteria (nutritional competition, mutual inhibition, synergy, etc.).

The intestinal flora is in a healthy balanced state (the number of probiotics in the large intestine is 1,000 to 10,000 times that of harmful bacteria), and pathogenic or conditional pathogens are present in very small numbers, and they produce toxic metabolites Not enough to cause harm to the health of the host. However, when the above-mentioned four factors change sharply, the number of beneficial bacteria in the intestine is greatly reduced, the number of harmful bacteria is increasing wildly, and the intestinal flora balance is broken, and the human body will develop symptoms such as diarrhea, constipation, and indigestion. The balance of the intestinal flora is broken, and the result is impaired health.

Therefore, in order to ensure the daily normal operation of the intestine, in addition to a reasonable diet and normal routine in daily life, there are sufficient prebiotics to proliferate beneficial bacteria in the intestine and keep the intestine healthy. The survey data shows that the average daily prebiotic intake of human body is 2-8g / d, which is still a certain distance from the minimum daily intake of human body15g. Therefore, the average person needs extra supplements to ensure the daily prebiotics required by the intestine. ^[4]

Gut flora health links

Gut flora causes obesity

A study led by Zhao Liping, State Key Laboratory of Microbial Metabolism, School of Life Science and Technology, Shanghai Jiaotong University shows that obesity may be caused by bacterial infections, rather than overeating, too little exercise or genetic factors, which may affect the public health system and the pharmaceutical industry. And the food manufacturing industry has a profound impact. ^[5]

The findings in China, after eight years of research by scientists around the world, explain the link between gut bacteria and obesity. "This is a very important phenomenon," said Professor Liping Zhao, a research team at Shanghai Jiao Tong University, who conducted the study. "This is the last previously missing evidence that bacteria cause obesity." Scientists found human bacteria associated with obesity, and They were fed to mice and their weight gain was compared to mice without bacteria. Although the latter were fed high-fat foods and prevented from exercising, they did not experience symptoms of obesity.

Other scholars who were not connected to the project quickly commented on the potential impact. Professor David Weinkove, a biology lecturer at Durham University, said: "If obesity is caused by bacteria, then it may be contagious, it may come from unknown environmental factors, or from parents In the end, it may have nothing to do with behavior. "Wenkoff believes that Professor Zhao's research has opened the way for interventional treatment of obesity, and may develop drugs for treatment.

Intestinal flora autoimmunity

Researchers from the Sick Children's Hospital of Toronto have found that exposure to gastrointestinal bacteria early in life can help mice prevent autoimmune diseases. The study also revealed why women are more at risk for autoimmune diseases such as multiple sclerosis, rheumatoid arthritis and lupus erythematosus than men. Related papers were published in the January 17 issue of Science.

The study, for the first time, identified the differences between normal intestinal microorganisms in female and male mice reared in the same environment, and demonstrated that transferring male intestinal bacteria to females at high genetic risk could prevent autoimmune diseases.

The second unexpected finding was to reveal the effects of gut microbiological treatment on sex hormones. When young female mice are exposed to normal gut microbes from adult males, their testosterone levels rise. Scientists later confirmed that this hormone is essential for the treatment of intestinal microbes to prevent the disease. It was found that the sex of animals determines the composition of their gut microbes, and that these microbes affect sex hormone levels, which in turn regulate an immune-mediated disease. ^[6]

Intestinal flora blood pressure regulation

One study found that by acting on two major short-chain fatty acid (SCFAs) receptors, olfactory receptor 78 (Olfr78) and Gpr41, short-chain fatty acids (SCFAs) produced by the intestinal microbiota may play a role in regulating blood pressure has an effect. Jennifer L. Pluznick and colleagues found that Olfr78 is expressed in the kidney and mediates renin secretion in response to short-chain fatty acids (SCFAs), particularly propionate. When mice were provided with propionate, their blood pressure showed a large and rapid dose-dependent decrease, and mice that knocked out Olfr78 were particularly sensitive to this effect, suggesting that the normal function of Olfr78 is to increase blood pressure. And fight against the hypotensive effect of short chain fatty acids (SCFAs). In contrast, mice lacking the Gpr41 gene had no hypotensive response to propionate, and this dose caused a strong hypotensive response in wild-type mice, suggesting that Gpr41 is involved in reducing blood pressure in response to propionate . Decreasing the intestinal microbiota biomass of Olfr78 knockout mice by giving antibiotics caused their blood pressure to increase, suggesting that propionate produced by the intestinal microbiota regulates blood pressure through the Olfr78 receptor. The authors suggest that studying gut microbiota and renal-cardiovascular crosstalk may help to better understand and treat hypertension. ^[7]

Gut flora treats allergies

Early microbial exposure and stimulation can affect the body's immune system development. The intestinal flora regulates the immune function of the body through various ways such as promoting the development of the intestinal immune system and inducing T cell differentiation to keep it in a balanced state, thereby avoiding or reducing the occurrence of immune-related diseases. The occurrence of allergic diseases is related to the inadequate development of the body's autoimmune system and the imperfect immune regulation mechanism. The intestinal flora can affect the body's immune system and the distribution of the flora in children with allergies is different than that in healthy children. Allergic diseases are associated with children. Some studies have reported that probiotics have positive significance for the prevention and treatment of allergic diseases and provide a new way for the prevention and treatment of allergic diseases. ^[8]

Gut flora fights cancer

Researchers in the United States and France discovered in December 2013 that the gut flora can also control the body's response to cancer treatment drugs.

Researchers from the Pasteur Institute in France and other institutions reported in the American journal Science that cyclophosphamide, a drug commonly used for cancer chemotherapy, can destroy the intestinal mucus layer and allow intestinal bacteria to enter the circulatory system, some of which reach the spleen and Bacteria in the lymph nodes promote the formation of immune cells, which attack cancer cells. But when researchers killed the gut bacteria in mice with antibiotics, cyclophosphamide's ability to indirectly stimulate immune cells was greatly reduced.

Another study published by Science at the same time as the National Cancer Institute showed that researchers selected cancer laboratory mice that were receiving chemotherapy and had a survival rate of 70%, and used antibiotics to kill their intestinal bacteria. As a result, the chemotherapeutic drugs ingested by these experimental mice no longer work, and their survival rate drops to 20% after two months.

Researchers tested oxaliplatin, a drug used to treat colon cancer. This drug works best when the test subject's gut bacteria are ideal. But when antibiotics are used to kill intestinal bacteria, the effectiveness of oxaliplatin is greatly reduced.

Generally speaking, doctors often need to use a large number of antibiotics to prevent infection in cancer patients, but research has found that antibiotics may affect the efficacy of anticancer drugs. The two studies also show that for different anticancer drugs, the types of intestinal bacteria that help them are different. Previous research has found that certain types of intestinal bacteria may also promote the development of intestinal cancer, and intestinal bacteria cannot be supplemented blindly. ^[1]

New research on intestinal flora

In a meta-analysis of the journal BioEssays, researchers from the University of California, San Francisco, Arizona State University, and the University of New Mexico concluded that these microbiota can affect their host's feeding patterns through the vagus nerve. The vagus nerve is a nerve that extends from the brain to the intestine, and the microbiome likes to "play around" with it. ^[9]

The intestinal flora controls the host's diet to survive and reproduce, but also to eliminate microbial competitors next door. The gut is the battlefield for these bacteria, and manipulating the host's brain to get specific foods is their main weapon. Sometimes they even endanger the host by causing the host to eat harmful food. Studies have found that people with less diverse intestinal flora (that is, one type of bacteria that kills others by manipulating the brain) are more likely to become obese.

The paper emphasizes that the intestinal flora is not the only factor in obesity, but the authors did find some studies suggesting that the microbiota may be contagious, including those bacteria that cause overeating.

So why can't we immediately use a bunch of antibiotics to genocide those bacteria in our intestines? Well, the paper explains this: These microbiota have important functions such as "nutrition intake and immune development", which means that they provide us with vitamins and minerals, and build our immune system as a living in our body s return. These microbiota also help the host digest specific foods. People living in Japan have a special type of bacteria that helps them digest seaweed. Some children in Africa who eat sorghum stalks have bacteria that help them digest cellulose.

Fortunately, with relatively simple dietary changes, everyone's microbiome can be easily controlled.

If you are concerned about the composition of your microbiota, please understand that changing it through your diet may only take a few minutes-this is the time it takes for your microbiota to evolve in your gut, and it is only 24 hours long-this is the intestine after a diet change The time it takes for the flora to rebuild itself. Changing the bacteria in your gut may help change your eating habits and vice versa.

"Because people can easily use prebiotics, probiotics, antibiotics, fecal transplants, and dietary changes to manipulate the microbiota, for problems that are difficult to solve by other methods, such as obesity and unhealthy diets, changing the microbiota provides us with an easy operation Solution. "The authors wrote in a statement.

In addition to making lives healthier, "actions against the microbiome can also prevent and treat a variety of diseases, including obesity, diabetes, and gastrointestinal cancers," Aktipis said. "The importance of microbiota to human health Sex, we are just beginning to understand the tip of the iceberg. "