Probiotics are defined as live bacteria or yeasts which when administered in sufficient quantities provide a benefit to the health of the host, ensuring the normal functioning of the gastrointestinal and urogenital systems, maintaining or restoring their normal flora.
Normally, the gut contains bacteria that were acquired through a process that begins at birth in the human body and is called colonization. The gut microbiome, which is unique to everyone, contains billions of these bacteria that are considered beneficial or “friendly” and the term probiotic is used for them.
The bacteria most commonly found in the human microbiome belong to the Lactobacillus and Bifidobacterium family, and there are also yeasts such as Saccharomyces boulardii.
Scientists describe bacteria in 3 words: genus, species and strain. For example “Bifidobacterium longum W11”, where bifidobacterium is the genus, longum is the species and W11 is the strain.
Probiotics are usually measured in colony-forming units (CFUs). In most studies, higher doses have been found to have better results. However, some probiotics may be effective at doses of 1-2 billion CFUs per day, while others may require at least 20 billion CFUs to achieve the desired results.
Prebiotics and symbiotics
Prebiotics are substances, mainly fiber (inulin, lactulose, fructoo-oligosaccharides-FOS), which are the “food” of probiotics and contribute to their smooth growth and maintenance.
Foods and dietary supplements that contain both probiotics and prebiotics are characterized as symbiotic.
What are the types of probiotics?
Many types of bacteria are classified as probiotics, each with different benefits. They are mainly classified into 3 groups:
- lactic acid bacteria – Lactobacillus (eg L. plantarum, L. paracasei, L. acidophilus, L. casei, L. rhamnosus, L. crispatus, L. gasseri, L. reuteri, L.bulgaricus),
- Bifidobacteria – Bifidobacterium (eg B. longum, B. breve, B. animalis, B. bifidum),
- the yeasts – Saccharomyces (S. boulardii)
In addition, enterococci – Enterococcus (E. faecium), bacilli – Bacillus (eg B. coagulans, B. subtilis, B. laterosporus), propionic bacteria – Propionibacterium (eg P. jensenii, P. freudenreichii), the lactococci – Lactococcus (eg L. lactis, L. reuteri, L. rhamnosus, L. casei, L. acidophilus, L. curvatus, L. plantarum), as well as the streptococci – Streptococcus (p. S. sanguis, S. oralis, S. mitis, S. thermophilus, S. salivarius) belong to the particularly beneficial species of probiotics.
How do probiotics work?
Although the exact mechanisms of action of probiotics are not known, several have been suggested. As mentioned earlier, the most commonly used probiotics include lactic acid bacteria, especially Lactobacillus and Bifidobacterium species. These bacteria produce lactic acid, acetic acid and propionic acid, which lower the intestinal pH and suppress the growth of various pathogenic bacteria, thus restoring the balance of intestinal flora.
Another mechanism of bacterial interference involves the production of various substances, such as hydrogen peroxide, organic acids, bactericides and bioactive substances, which are toxic to pathogenic microorganisms.
Probiotics also reduce the colonization of pathogenic microorganisms in the urinary and gastrointestinal tract, competitively preventing their attachment to their endothelium. Lactobacilli have been shown to inhibit the attachment of E. coli (responsible for 99% of urinary tract infections) to uroepithelial cells.
Another proposed mechanism of action of probiotics involves immunomodulation. Animal studies have shown that certain probiotic strains increase the body’s immune response by stimulating the phagocytic activity of lymphocytes and macrophages. Probiotics contribute to the production of antibodies and are beneficial in treating diarrhea caused by gastroenteritis.
What probiotics are necessary in each condition?
Probiotics and constipation: In recent years dietary changes and probiotic supplements have become increasingly popular alternative approaches to treating constipation. Specific strains such as B. (animalis) lactis, L. reuteri, L. acidophilus, L. paracasei, L. delbrueckii subsp. bulgaricus, L. plantarum, B. longum, B. infantis, B. breve, S. thermophilus, L. casei Shirota, seem to act beneficially in the treatment of constipation.
Probiotics and diarrhea: Probiotics are widely known for their ability to prevent or reduce the severity of diarrhea. Diarrhea is a common side effect of taking antibiotics. It occurs because antibiotics can upset the balance between “good” and “bad” bacteria in the gut. Research has shown that taking probiotics reduced antibiotic-related diarrhea by 42%.
Probiotics can also help with other forms of diarrhea that are not related to antibiotics. A large review of 35 studies found that some strains of probiotics can reduce the duration of infectious diarrhea by an average of 25 hours. In addition, they reduced the risk of travelers’ diarrhea by 8%. They also reduced the risk of diarrhea from other causes by 57% in children and 26% in adults.
Efficacy varies, depending on the type and dose of probiotic taken. Strains such as Lactobacillus rhamnosus, Lactobacillus casei, Lactobacillus rhamnosus GG, Lactobacillus acidophilus, Lactobacillus bulgaricus and Saccharomyces boulardii are responsible for preventing or treating diarrhea.
Probiotics and Irritable Bowel Syndrome: Irritable bowel syndrome is characterized by diffuse abdominal pain, bloating, and impaired bowel function (alternating diarrhea and constipation). These symptoms may be due to bacterial overgrowth in the small intestine, causing increased fermentation and gas production reactions. Some studies suggest that probiotics may be helpful in reducing the flatulence associated with this syndrome. The most commonly used probiotics in its treatment include the Lactobacillus and Bifidobacteria groups.
Probiotics and urinary tract infection: Abnormal vaginal microbiome can lead to symptomatic infections, including vaginal candidiasis. Lactobacilli, especially Lactobacillus crispatus and Lactobacillus iners, L. rhamnosus, L. plantarum, L. acidophilus, and L. reuteri are the predominant vaginal microorganisms in healthy premenopausal women. When the normal vaginal microflora is disturbed, as with the use of broad-spectrum antibiotics, overgrowth of Candida albicans can occur, causing vaginal candidiasis. Restoration of normal flora with lactobacilli can help treat this infection, as well as prevent the migration of pathogenic bacteria and especially E. coli to the walls of the urinary system.
Probiotics and Immune: Some probiotics have been shown to promote the production of natural antibodies in the body.
A literature review found that taking probiotics reduced the likelihood and duration of respiratory infections. However, the quality of the evidence was low.
Another study of more than 570 children found that taking Lactobacillus rhamnosus reduced the incidence and severity of respiratory infections by 17%.
Probiotics and overall health: Intestinal bacteria are involved in the digestion of food, in the absorption of nutrients, and many of them produce certain vitamins themselves, such as vitamin B12, B6 and Vitamin K, which are absorbed and used by the organization. The role of probiotics in the metabolism of macronutrients (eg carbohydrates) and many minerals and trace elements such as iron, calcium and magnesium is important.
A recent study in healthy adults showed that taking Bifidobacterium bifidum for four weeks helped boost the production of beneficial fatty acids (short chains).
It is known that in the elderly there is a decrease in “friendly” intestinal bacteria and in particular Bifidobacteria, along with an increase in “hostile” bacteria with consequent health problems. For this reason it is most often recommended to take fortified probiotics, in addition to their diet.
Method of administration and storage of probiotics
Probiotics are available as a dietary supplement (eg tablets, capsules or powders) and as fermented dairy products (ie yogurt and milk). Their effectiveness depends on their ability to survive through the gastrointestinal tract and colonize a portion of tissue. To prevent their destruction by gastric acids and intestinal bile salts, some probiotic preparations may be enteric coated. For colonization to occur, probiotics must contain live microorganisms and must be taken on a regular basis in order to achieve effective concentrations in the body. The quantity, quality and purity of bacteria or yeast in probiotics can vary between products due to the complexity of quality control with live microorganisms and the lack of universal quality assurance programs.
The probiotic dosage varies depending on the product and usually, a probiotic should contain several billion microorganisms to increase the chance of adequate colon colonization. For lactobacilli, the typical doses used in studies ranged from 1 to 20 billion CFUs. For S. boulardii, most studies have examined daily doses ranging from 250 to 500 mg. Products should be stored according to the manufacturer’s recommendations, as some may require refrigeration. In addition, the preparations may have a limited shelf life and many preparations contain many different species, so the dosage may vary depending on the product. It is recommended to be consumed on a full stomach to minimize the effect of stomach acids on probiotics, unless otherwise stated by the manufacturer.
Avoid taking them with hot drinks, as most of them are destroyed at high temperatures.
Contraindications and interactions
Consult your doctor if you are being treated with immunosuppressive and chemotherapeutic drugs, as probiotics could cause infection or pathogenic colonization in immunocompromised patients. Otherwise, probiotics are considered safe formulations without significant side effects and interactions.
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