Digestion, General | June 30, 2014 | Author: The Super Pharmacist
Probiotics are defined as "live microorganisms which when administered in adequate amounts confer a health benefit on the host." Early in the 20th century, investigators first discovered that intestinal flora could be altered, and harmful microbes could be replaced with beneficial bacteria.
Probiotics, which are regulated as dietary supplements and foods, consist of yeast or bacteria. They are available as capsules, tablets, packets, or powders and are contained in various fermented foods, most commonly yogurt or dairy drinks.
Probiotic products may contain a single microorganism or a mixture of several species. The most widely used probiotics include lactic acid bacteria, specifically Lactobacillus and Bifidobacterium species. The yeast Saccharomyces boulardii also appears to have health benefits.
It is noteworthy that probiotic effects tend to be specific to a particular strain, so a health benefit attributed to one strain is not necessarily applicable to another strain, even within one species. Therefore, generalisations about potential health benefits should not be made.
The strongest evidence for the use of probiotics lies in the treatment of certain diarrhoea diseases, especially rotaviral diarrhoea in children. Studies are inconsistent regarding the efficacy of probiotics for antibiotic-associated diarrhoea and travelers' diarrhoea. Although clinical trial results are conflicting, probiotic therapy may also be beneficial in the treatment of Crohn's disease, ulcerative colitis, irritable bowel syndrome, and Helicobacter pylori infections.
Probiotics have also been shown to decrease the symptoms of lactose intolerance.
Some studies have suggested the benefit of probiotics in the treatment of vulvovaginal candidiasis, but these studies had important methodological limitations, including small sample sizes, inadequate controls, and lack of blinding.
Irritable bowel syndrome, characterised by abdominal pain, bloating, flatulence, and altered bowel habits, may be due to bacterial overgrowth in the small intestine, causing increased fermentation activities and gas production. Some studies suggest that probiotics may be beneficial in reducing bloating and flatulence associated with this condition. However, limitations exist in interpreting study results due to the lack of standardization of strains, dosages, treatment durations, and assessment of clinical outcomes.
Several studies have found that probiotics have a beneficial effect on atopic eczema. Kalliomaki et al20 conducted a double-blind, randomized, placebo-controlled trial where pregnant women were given probiotics or placebo.
The study demonstrated a 50% reduction in the frequency of atopic eczema during the first two years of life in the children born to mothers on probiotics compared with placebo (23% versus 46%). This cohort was re-examined after four years, and significantly fewer children who had previously received Lactobacillus rhamnosus GG were diagnosed with atopic eczema.
This suggested the protective effect of this probiotic on atopic eczema in at-risk children continues beyond infancy.
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Decrease intestinal pH: The most frequently used probiotics include lactic acid bacteria, particularly 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, thereby reestablishing the balance of the gut flora.
Toxin production: Another mechanism of bacterial interference involves the production of various substances, such as hydrogen peroxide, organic acids, bacteriocins, and biosurfactants, that are toxic to pathogenic microorganisms. One probiotic with this ability is Lactobacillus species strain GG, which has been shown to secrete a low-molecular-weight compound that inhibits a broad spectrum of gram-positive, gram-negative, and anaerobic bacteria. The nonpathogenic yeast, S. boulardii, may have a role in Clostridium difficile infection by producing a protease that decreases the toxicity of C. difficile toxins A and B.
Block epithelial attachment: Probiotics also decrease colonisation of pathogenic organisms in the urinary and intestinal tracts by competitively blocking their adhesion to the epithelium.
Immunomodulation: Another proposed mechanism of action of probiotics involves immunomodulation. Animal studies have found that some probiotic strains augment the immune response by stimulating the phagocytic activity of lymphocytes and macrophages.
When ingested orally, probiotics are generally considered safe and well tolerated. The most common adverse effects include bloating and flatulence; however, these are typically mild and subside with continued use. Constipation and increased thirst have also rarely been associated with S. boulardii.
One theoretical concern associated with probiotics includes the potential for these viable organisms to move from the gastointestinal tract and cause systemic infections. Although rare, probiotic-related bacteremia and fungemia have been reported.
The most important thing is to determine what type of probiotic microorganism is needed for a specific condition.
Probiotic benefits associated with one species or strain do not necessarily hold true for others.
Their efficacy relies on their ability to survive passage through the gastrointestinal tract and colonise.
To prevent destruction by gastric acid and intestinal bile salts, some probiotic preparations may be enteric coated or microencapsulated.
For colonisation to occur, probiotics must contain living, viable organisms and must be ingested on a regular basis in order to maintain effective concentrations.
Unfortunately, the manufacturing process may cause living organisms to become nonviable, thus reducing probiotic effectiveness. The quantity, quality, and purity of the bacteria or yeast in probiotics can vary among products due to the complexity of quality control with live microorganisms and the lack of universal quality-assurance programs.
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