Substances Impacting Gut Microbiota

The digestive tract is the second largest complex system in the human body. It is a habitat for naturally occurring microbes. The diversity of microorganisms within it is so great that the digestive genome is recognized as the third largest mammalian genome, following only the nuclear and mitochondrial genomes. However, a vast number of bacteria inhabiting the digestive tract have been confirmed by many scientific studies. The gut microbiome is a rich and dynamic ecosystem, evolving throughout human life. Conditions in the digestive tract are ideal for the life and growth of not only naturally occurring bacteria, but also those we provide through food. The gut microbiome is unique to each individual. It is often compared to a fingerprint, which is known to be unique. It is not possible to determine which microorganisms and in what quantity should be part of it. It is relatively stable, but can change under the influence of factors such as age, diet, applied antibiotics, or metabolites produced by bacteria. Disruptions in the microbiome can lead to the development of many diseases, such as inflammatory bowel disease, allergies, obesity, or cancer.

– harmful microorganisms – that is, producing toxic metabolites that disrupt the proper functioning of the digestive system, such as Shigella, salmonella, some species of clostridium; – potentially harmful microorganisms – whose negative effect on the human body is manifested in the case of disorders in the digestion system such as Escherichia coli, Klebsiella pneumoniae; – beneficial microorganisms – that not only play a role in important processes in the body but also inhibit the growth of pathogenic bacteria, such as Lactobacillus, Bifidobacterium. The composition and proportion of bacteria in these groups depend on many factors, including the host's diet and genome. Studies have shown that the microbiomes of adult residents of Japan and America differ from each other. It has been observed that children born in developing countries have a more diverse bacterial flora than those born in Western European countries. Differences between people living in rural and urban areas have also been noted, which is most likely due to differences in their diet. It has also been shown that a diet rich in protein and low in carbohydrates can affect the bacterial composition of the colon microflora and thus the health status of the host. It has also been proven that reducing the amount of carbohydrates consumed leads to a decrease in the number of bacterial cultures producing lactic acid, while a carbohydrate-rich diet promotes an increase in the total number of bacterial cells.

Maintaining a microbiological balance among the various bacterial groups in the digestive tract is crucial for health. This enables gut microbes to perform a range of tasks such as inhibiting the growth of undesirable bacteria, supporting the digestion and nutrient absorption process, stimulating the synthesis of immune proteins (immunoglobulin A, interferon), vitamin K and B synthesis, participating in fermentation leading to the production of short-chain fatty acids, which serve as an energy source for intestinal epithelial cells, improving the bioavailability of sodium, calcium, magnesium, potassium, non-heme iron, influencing normal intestinal peristalsis - alleviating digestive discomforts such as nausea, bloating, abdominal pain, diarrhea and constipation - as well as indirectly affecting cholesterol and fatty acid metabolism.

Milk fermentation bacteria have been used by humans for centuries. The ancient Greeks and Egyptians also utilized acidic milk. In 1987, Louis Pasteur proved that the use of milk fermentation was dependent on microorganisms. According to some sources, the Roman writer and naturalist Pliny the Elder recommended drinking fermented milk drinks to reduce digestive discomfort. The inhabitants of the Balkan region, who enjoyed an above-average lifespan, had a diet rich in fermented milk drinks such as kefir, acidic milk, and yogurt, which contained lactic acid bacteria strains that positively affected human health. The term probiotic originates from the Greek 'pro bios,' which means 'for life.' The person who likely introduced the term probiotic was Ferdinand Vergin, who compared the destructive effect of antibiotics on the gut microbiota with the positive impact of beneficial probiotic bacteria in his 1954 article 'Anti-Und Probiotika.' A few years later, Lilly and Stillwell used the term probiotic in their work describing microorganisms that stimulate the growth of other organisms. Probiotics are microorganisms that include not only lactic acid bacteria strains (Lactobacillus spp., Streptococcus spp., Bifidobacterium spp.) but also yeast strains (Sacharomocyces spp.) and mold cultures (Aspergillus spp.). The positive effect of probiotics on the body is invaluable.

– prevent diarrhea and other adverse reactions after radiation therapy and antibiotic treatment, – treat constipation, reduce the level of enzymes in the stool, – protect against intestinal disorders, – treat diarrheal infections caused by rotavirus infections, – protect against food mutagenic agents, – stimulate the immune response, – regulate the intestinal flora, – prevent acute bacterial diarrhea, – alleviate the course of Crohn's disease, – have the ability to produce the enzyme lactase, – prevent recurrent inflammation of the vagina, – have anti-inflammatory properties, help fight Helicobacter pylori infections, – inhibit the pathogenic activity of the intestinal flora, – treat candidiasis and dental caries, – regulate intestinal peristalsis, treat constipation, – prevent allergies (especially atopic dermatitis), – reduce the absorption of cholesterol from food, – reduce the carcinogenic agent in the gastrointestinal tract, – have a positive effect on gastrointestinal disorders, including irritable bowel syndrome and intestinal inflammation. However, it should be noted that the therapeutic application of probiotics depends on the strain, but also on the type of carrier used and the growth conditions in the large intestine. The latter is mainly determined by the host's diet. A diet rich in oligosaccharides provides ideal conditions for the growth of the large intestine flora. The positive effects on the growth of the intestinal flora have prebiotics, which are food components that are resistant to digestive enzymes and whose action consists in stimulating the growth and activity of intestinal bacteria. Prebiotics naturally occur in food or are artificially added. These include, among others: inulin, fructooligosaccharides, lactulose, galactose derivatives, and many others. Due to the natural occurrence of some probiotic bacterial strains in the intestinal flora (Lactobacillus and Bifidobacterium), their application should not cause negative side effects. Nevertheless, monitoring the body during the use of probiotic preparations is of great importance. Cases of unwanted effects of lactic acid bacteria are very rare. In recent years, infections caused by the use of preparations, in which the strains Lactobacillus and Bifidobacterium were included, accounted for 0.05-0.4% of cases of endocarditis and bacteremia.

The market is currently flooded with a wide range of food and drug products containing probiotics in their composition. Pharmaceutical products are typically available in the form of tablets, capsules, or packets containing biomass of bacteria that have undergone lyophilization. Food products that are naturally rich in probiotics are dairy products subjected to lactic acid fermentation, such as sour milk, kefir, yogurt, and acidic milk. Lactic acid bacteria are also widely used in the cheese industry, where they play a critical role in the ripening process of cheese and impart specific organoleptic properties. However, many people are unable to consume these products due to allergies to cow's milk proteins or due to following a vegan diet. An alternative are plant-based products enriched with probiotic bacteria. The most commonly used plant-based products subjected to fermentation are soy products, vegetables, and fruits (juices, purees). Other products containing probiotics include infant powdered milk, cereal products, and dairy products. In stores for healthy food, available are breakfast cereals, bread, oat drinks, boza (a Balkan drink), and bran enriched with probiotic microorganisms. An interesting fact is that probiotics can also be found on carriers that are not associated with the pharmaceutical industry, such as special membranes attached to straws or bottle caps. Probiotics enter food directly during drinking through a straw or after shaking the bottle with the drink before opening. Although probiotic products have been known for a long time, they have only become popular on the market in recent years. This process is mainly due to the growing consumer awareness of healthy eating and the emergence of an increasing number of scientific studies confirming the effectiveness of probiotics in improving health.