Common probiotics mainly refer to two major groups of lactic acid bacteria: one is bifidobacterium, common are Bifidobacterium infantis, Bifidobacterium longum, Bifidobacterium breve, Bifidobacterium adolescentis, etc.; the other is lactobacilli, such as Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus rhamnosus, Lactobacillus plantarum, and Lactobacillus reuteri. The probiotics used in humans include Bifidobacterium, Lactobacillus, Bacillus and Yeast. In terms of safety, currently industrial probiotics are mainly derived from healthy humans, animals and traditional foods (fermented dairy products, kimchi, natto and other fermented foods).
1. The relationship between probiotics and intestinal flora and the mechanism of regulating intestinal flora
There are about 500 species in the human intestine, about 1010 bacteria. Under normal circumstances, it will not cause human diseases or other unhealthy phenomena, because these microorganisms constitute the normal flora of the human intestine, and most of them are beneficial bacteria. The relationship between gut microbiota is complex, some are alternate, some are antagonistic, and they are grown as nutrients by the foods taken up by the host and the various components secreted into the digestive tract, and they multiply continuously and are excreted. They are closely related to the host's health and disease. Under normal conditions, the composition, type, and quantity of the intestinal flora are relatively stable. The intestinal flora not only constitutes a protective barrier with the intestinal mucosa, prevents the invasion of harmful bacteria, viruses, and food antigens, but also stimulates the intestinal tract. The immune organs play a stronger immune function. Among all the bacteria, probiotics are the dominant bacteria that can bind tightly with the intestinal mucosa, constitute the intestinal biologic barrier, and can pass through the space-occupying effect, nutrient competition, and various metabolites and bacteriocins secreted by them, etc. To inhibit the overgrowth of pathogenic bacteria and the invasion of foreign pathogenic bacteria plays an inestimable role in maintaining the microecological balance of the intestine.
The time and space for various intestinal microbes to adhere in the intestine are not the same. Specific bacteria adhere to specific parts of the intestinal mucosa. After the probiotics adhere to the site, they colonize and continue to multiply until a stable flora is formed. , which is the effect of probiotics.
The probiotic itself belongs to the normal intestinal flora. When it is stably adhering to the intestine, the probiotic begins to reproduce. It can use its own specific enzymes to supplement the deficiency of the host on digestive enzymes. With limited nutrients, probiotics can competitively consume potentially pathogenic nutrients through their predominant growth. This is the nutritional competition and antagonistic effect of probiotics.
Probiotics multiply in the intestine and will continue to produce a variety of their own metabolites, many of which have a strong inhibitory effect on pathogenic bacteria. Such as Lactobacillus can produce a large number of short-chain fatty acids, hydrogen peroxide, etc., have antibacterial or bactericidal activity; there are some probiotics can produce a broad spectrum antibacterial substances, such as bacteriocins, lipophilic molecules, etc. The harmful bacteria in the road have inhibitory or killing effects.
2. Mechanism of immunomodulatory effects of probiotics
In 1885 Pasteur proposed the relationship between the immune system and microorganisms. The cell wall of Gram-negative bacteria contains peptidoglycan (PG), lipopolysaccharide (LPS) and polysaccharide (PS), and the positive bacteria contain teichoic acid (LTA). LPS, these macromolecular components are the main material basis for the bacteria to exert physiological functions on the host. Its role includes the adhesion and colonization of bacteria to host cells, immune induction, and prevention of tumorigenesis. In the course of bacterial proliferation and death, both LPS and PG macromolecules are continuously released, while in the case of bacterial infection, LPS and PG enter the bloodstream.
There is a well-developed immune system in the human intestine. The current study found that the microorganisms that act as probiotics in the gastrointestinal tract stimulate the immune system through three main ways: First, as living cells colonize and multiply on the surface of the gastrointestinal tract. The quantity can stimulate the immune system; the second is that the antigen material released after cell death is lysed and absorbed directly stimulates the immune system; and thirdly, it affects the immune system indirectly by affecting the composition of microbial flora in the gastrointestinal tract. The improvement of human immunity by probiotics is mainly reflected in three aspects: first, to promote macrophage phagocytosis of microbial cells and carbon particles, enhance macrophage activity; second, to raise the level of antibody production in the immune system; third, to increase the intestinal wall Mucosal cell surface local antibody levels. In summary, the stimulation of immunity by probiotics includes both cellular and humoral immunity. Cellular immunity is an immune response centered on T cells in lymphocytes, and humoral immunity is an immune response in which a specific antibody plays a major role.
3. The dual effect of probiotics and prebiotics.
Prebiotics are specific foods for beneficial bacteria in the intestine and cannot be used by harmful bacteria. They cannot be hydrolyzed and absorbed by the human body and can reach the large intestine directly. Prebiotics promote the proliferation of beneficial bacteria by crowding the human intestinal space, or activate their metabolic functions and inhibit harmful bacteria. In addition, prebiotics also promote the absorption of nutrients such as calcium, magnesium and phosphorus.
The role of probiotics and prebiotics is not independent of each other. They are used simultaneously and have an effect of 1+1>2. The simultaneous use of probiotics and prebiotics has a better effect on gut health than single use of probiotics or prebiotics because of the synergistic effect of living probiotics and specific selective substrates, prebiotics. Prebiotics act as probiotics in the gut and cannot be used by harmful bacteria, but they can promote the growth and reproduction of beneficial bacteria, thereby promoting the competition of probiotics to become dominant bacteria and inhibiting the growth of harmful bacteria. Probiotics and prebiotics work together to maintain a balance between the microecological environment of the intestine, prevent and improve constipation and diarrhea, improve immunity and maintain human health.
It should be noted that in order for probiotics and prebiotics to perform their dual effects better, the amount of living probiotics added to the human body must reach a certain amount, and scientific research has proven that the number of viable bacteria of 20 billion can already exert its effect. (1010 The international advanced level has reached 30 billion live bacteria, and China has already had more than 30 billion probiotic products). Moreover, the greater the number of live bacteria, the greater the health effects on the human body. In addition, attention should be paid to the selection of prebiotics. Inulin, oligofructose, and resistant dextrins are all good prebiotics. Dietary fibers such as cellulose and dextran are not prebiotics because they can be beneficial bacteria. Use, can also be used by harmful bacteria, there is no selectivity of prebiotics; Because single-component prebiotics can not fully exert its physiological effects, you need to choose a compound prebiotic containing a variety of prebiotic components, can improve the overall intestine The composition of the probiotics rapidly, continuously and effectively proliferates the probiotics. For example, a certain amount of inulin, fructo-oligosaccharides, galacto-oligosaccharides and xylo-oligosaccharides have the effect of promoting calcium absorption. Reasonable use of probiotics and prebiotics, give full play to the double effect.
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