Probiotics are not only the subject of extensive scientific research, but also represent an important product on the world market. Today, hundreds of probiotic food products and nutritional supplements are available to a wide range of consumers, whose manufacturers promise a solution to a wide variety of health problems. Food supplements containing probiotics, according to distributors, will relieve you of constipation and fatigue. Pill bottles containing special combinations of bacteria are shown to be anti-cancer and lower cholesterol. Well, who does not believe in getting rid of all diseases, starting with indigestion and ending with migraine, when taking traditional foods containing microbes, such as kombucha (fermented tea containing cultures fungi and bacteria) and kefir (fermented milk drink)? The global probiotic market is estimated to be billions of dollars a year. But what does the evidence-based medicine think about probiotics? Do they have a positive effect on human or animal health? Or maybe their properties are exaggerated? After all, is it also possible that they can do a lot of harm?

The American Academy of Microbiology organized a conference in November 2005, attended by 38 specialists in various fields. They discussed the relationship between microorganisms, immunity and disease, evidence regarding the healing properties of probiotics and the possible prospects for their use. This article summarizes the discussion.

probiotics are living microorganisms which, when given in sufficient quantities, have a positive effect on health.

A thorough study in experimental and clinical conditions has demonstrated certain effects of probiotics, but the efficacy and reproducibility of therapeutic measures using probiotics have not yet been confirmed.

It should be noted that some formulations of probiotics have had a negative effect on health. Like any immune reaction, the immune response to the microorganisms that make up probiotics can have both positive and negative effects. For example, the use of Lactobacillus rhamnosus GG (LGG) in patients with Crohn's disease has actually made some of them worse. In another study in which LGG was administered perinatally to children, the bacteria caused a significant reduction in the incidence of atopic dermatitis at the age of 2 and 4 years, but they also led to a slight increase (but statistically unreliable) the frequency of allergic reactions of the respiratory tract at the age of 4 years.

It is difficult to cause long-term changes in the microflora formed in the human intestine. In the experiments, the introduction of bacteria resulted in a change in the composition of the microflora for a short time, but the original composition was quickly restored. The composition of the intestinal microflora is restored after treatment with antibiotics. The microflora is easier to change in children who are going through the neonatal colonization stage and in whom the composition of the microflora is simpler than in adults with an established complex composition of the microflora.

The use of probiotics can cause the population size of certain types of bacteria to change. For example, the use of strains of Lactobacillus rhamnosus temporarily changes the number of lactobacilli and entorococci in the feces, without affecting other bacteria. It should be remembered that studying fecal samples may not provide information about the changes in the small intestine caused by probiotics.

Prebiotics (carbohydrates, which are nutrients for certain types of fermenting microorganisms in the gut) may have a greater effect on the microflora than probiotics. Prebiotics are consumed mainly by strict anaerobes, which contributes to the growth of their population. The widely used prebiotic inulin helps to increase the population of bifidobacteria.

Probiotics are mainly used as prophylactics and concomitant therapy, and are not the main treatment for diseases. When using probiotics as the main treatment, many examples of their positive effects are described, but the effect of most formulations is weak and difficult to distinguish from the placebo effect during the evaluation.

Given the potential danger associated with the use of living microorganisms, including the development of infection, a promising step is the replacement of living microorganisms with individual components of microbial cells and bacterial metabolic products. This approach could be more effective. When bioactive molecules that provide the action of effective probiotics are identified, these molecules can be used in purified form. The metabolic products derived from the bacteria that make up probiotics that can be used for therapeutic purposes include short chain fatty acids, cell wall peptidoglycan and DNA.

Currently in the United States, no probiotics are registered as a biological drug used to treat, prevent, or diagnose human disease. Probiotics are produced according to standards designed for food, not higher standards for organic products. The probiotics available are often of poor quality. The microorganism listed on the label may not be present in the product or may be present in small quantities.

The search for microorganisms that can be used as probiotics is a long and complex process. The composition of the probiotic must first of all be sure. The microorganism should not be pathogenic and special attention should be paid to the possibility of developing infection and immunodeficient people. The culture included in the probiotic must not carry plasmids containing the genes responsible for antibiotic resistance, since these genes can be transmitted to pathogenic microbes in the patient's body. Microorganisms must be resistant to acid and bile to reach the intended colonization area. It is necessary to use in vitro and in vivo models to clarify the mechanism of action of probiotics.

At this stage, there is a need for carefully planned (randomized, placebo-controlled) clinical trials of probiotics, in which the patient's microflora will be extensively studied, the endpoints will be clearly defined, and well-informed patients will accept accept treatment.

Each effect attributed to the probiotic must be associated with a specific strain within its composition. The characteristic effects of a particular strain should not be transferred to other strains of the same species. It is necessary to study the mechanisms of action of each probiotic in order to know if their activity under various physiological and pathological conditions can be explained by general mechanisms.

Microorganisms play an important role in maintaining our health. Despite this, the general population, especially in the United States, is afraid of microbes, which are considered "dirt", which should not be in the body and in the home. This misconception must be corrected through public education programs.

Bacteria in the body inevitably interact with each other, and this interaction can play a crucial role in maintaining health. The ability of probiotics to interfere with these interactions requires studying different types of normal microflora (including young children, the elderly, and the immunodeficient) to ensure the safety of prescribed probiotics. An understanding of the fundamentals of microorganism ecology is necessary.