Probiotics is a term used to describe supplementation with the friendly bacteria of the large intestine; the most important of which are lactobacillus acidophilus and bifidobacteria. The official definition of the term probiotic (as defined by Havenaar and Huis In’t Veld) is described as “microorganisms in sufficient numbers, which alter the microflora (by implantation or colonization) in a compartment of the host and by that exert beneficial health effects in this host.”
The health effects attributed to the use of Probiotics are numerous. Well documented effects include lower frequency and duration of diarrhea associated with antibiotics, rotavirus infection, chemotherapy, and to a lesser degree traveler’s diarrhea; stimulation of humoral and cellular immunity; and decrease in unfavourable metabolites in the bowel that are linked to colon cancer development (ammonium and procarcinogenic enzymes). Other health benefits are also related to the use of Probiotics as reviewed below.1,2
It has been shown that lactobacilli inhibit the growth of less desirable organisms in the large intestine through competition for nutrients, alteration of pH and oxygen tension to levels less favourable to pathogens (disease-causing organisms), prevention of attachment of pathogens by physically covering attachment sites, and production of limiting factors such as antimicrobial factors.1,3,4
The gut microflora (normal bacterial population) is an important constituent in the intestine’s defense barrier, as demonstrated by increased antigen transport across the gut mucosa in the absence of an intestinal microflora. The gut microflora also elicits specific immune responses at a local and systemic level. A healthy composition of microflora has also been shown to tone-down hypersensitivity reactions involving food allergies, infant atopic dermatitis, autoimmune conditions (rheumatoid arthritis, juvenile arthritis), and inflammatory bowel conditions.
In general, evidence exists to show that probiotic supplementation reduces the entry of pathogens and antigens from reaching the bloodstream. Supplementation with probiotics tends to stimulate and enhance systemic immune function in healthy individuals, while toning-down (down-regulating) the exaggerated immune reactions that contribute to food allergies and inteolerance, atopic dermatitis (eczema), certain autoimmune diseases and inflammatory bowel conditions such as Chrohn’s disease and ulcerative colitis, as noted above.
In one placebo-controlled trial, patients with pouchitis (inflammation of the ileal pouch-anal anastamosis after colectomy) had fewer episodes of clinical relapse when treated with Probiotics, and had clinical outcomes as good as those treated with the anti-inflammatory agent mesalamine.
Probiotic supplementation has also been shown to reduce the secretion of pro-inflammatory cytokines (particularly, tumor necrosis factor alpha) from white blood cells that promote inflammatory responses in conditions such as atopic dermatitis. At the same time, Probiotics stimulate the release of interferon gamma which has positive effects on the gut, preventing inflammation, and providing systemic benefits as well.5,6
One researcher states “these data point to the conclusion that Probiotics can be used as innovative tools for treating dysfunction of the gut mucosal barrier, including acute gastroenteritis, food allergy, and inflammatory bowel disease. Many of the probiotic effects are mediated via immune regulation, in particular by control of the balance of pro-inflammatory and anti-inflammatory cytokines.
Clinical Application and Mechanism of Action
1. Post Antibiotic Therapy
During and after antibiotic therapy supplementation with a mixture of bifidobacterium bifidum and L. acidophilus can prevent the candida overgrowth, diarrhea and urinary tract infections that can result from antibiotic therapy.
Probiotic supplementation can maintain or re-establish the bacterial flora equilibrium during or after treatment with ampicillin. Research exists to support the use of probiotic supplementation during antibiotic administration.1,3,7,8,9
2. Fibrocystic Breast Disease (FBD) and Premenstrual Syndrome (PMS)
To improve the excretion of estrogen conjugated with glucuronic acid some practitioners recommend the ingestion of 10-20 billion L. acidophilus living organisms per day. L. acidophilus inhibits the overpopulation of the bacteria that secrete beta-glucorinadase enzyme, which in turn deconjugates estrogen from glucuronic acid.
In this instance, estrogen can be re-absorbed back into the bloodstream (entero-hepatic pathway) and over stimulate metabolic processes that exacerbate FBD and PMS.
Research supports the view that FBD and PMS are aggravated and possibly caused by a high estrogen to progesterone ratio. Improving estrogen detoxification and intestinal excretion of estrogen has been shown to improve symptoms of FBD and PMS.10
Gastroenteritis is the main cause of acute diarrhea. It is usually due to viral or bacterial pathogens or to parasites, but the most frequent cause in children is rotavirus. A number of clinical trials have shown that supplementation with Probiotics (especially with Lactobacillus rhamnosus), is effective in shortening the duration of this condition, particularly in infantile gastroenteritis. Other studies have shown that probiotic supplementation can reduce risk of diarrhea in children admitted to hospital.11
4. Traveler’s Diarrhea
Acute diarrhea occurs in half of travelers who visit high-risk areas. Although most cases are mild and self-limiting, there is considerable morbidity. Some, but not all, studies indicate that the use of probiotic supplementation can reduce the incidence of traveler’s diarrhea (from 71% to 43% in one study).11
5. Irritable Bowel Syndrome and Inflammatory Bowel Disease
Limited evidence exists to support the use of Probiotics for the treatment of irritable bowel syndrome, other than to control symptoms of diarrhea in some cases. Evidence is stronger to support the use of probiotic supplementation for ulcerative colitis and Crohn’s disease. In a study of 120 ulcerative colitis patients, comparable results were seen in relapse of the disease in patients receiving probiotic supplementation as compared to those taking the anti-inflammatory drug, mesalamine. A second study involving 116 ulcerative colitis patients revealed similar findings. As noted above, patients with pouchitis have also experienced benefit from the use of Probiotics, with respect to a reduction in inflammation and pain. In general, the positive effects upon immune function and the suppression of the inflammatory process are likely the ways in which Probiotics reduce relapse of inflammatory bowel disease and help to effectively manage pouchitis and related inflammatory conditions of intestinal tract.
1. Concurrent or Post Antibiotic Therapy: 15-20 billion living organisms per day8,9
2. Fibrocystic Breast Disease and Premenstrual Syndrome: 5-10 billion living organisms per day7
3. Gastroenteritis, (Prevention of Traveler’s Diarrhea), Ulcerative Colitis, Crohn’s Disease: 10 billion living organism per day.
Adverse Side Effects and Toxicity
Amounts exceeding 10 billion living organisms per day may lead to mild gastrointestinal disturbances. Probiotics are extremely safe with no toxicity reported at the above recommended doses. Some probiotic preparations contain the yeast organism Saccharomyces boulardii. In patients with compromised immune status, this organism has produced severe, invasive fungal infections. In otherwise healthy individuals this yeast has been shown to work synergistically with other Probiotics, producing positive health outcomes.
L. acidophilus and B. bifidum are negatively affected by alcohol and antibiotics.14 They may also interfere with the metabolism of sulfasalazine, chloramphenicol palmitate, and phthalylsulfathiazole, especially L. acidophilus
Author's Note on Quality Assurance
Unlike other types of supplements that can have their potencies confirmed by third party analytic methods, when purchasing a probiotic supplement it is impossible to know the true potency of the product. This is due to the fact that many variables can affect the number of live bacteria that exist within the capsules at any given time. As a rule, Probiotic supplements should be refrigerated from the time they are encapsulated until the time they are purchased by the end user in order to slow down the division rate (germination rate) of the bacteria, as bacteria can only multiply a fixed number of times before death of the bacteria occurs. Unfortunately, most probiotic supplements are not refrigerated during shipping and transportation to distribution centers and on route to retail outlets, or during direct shipment to consumers (e.g. Internet sales, catalog sales, shipped directly to the consumer’s home by mail or courier). Thus, it is thought that a large number of probiotic products sold in the market place contain no live bacterial cultures or a minimal concentration, by the time consumers begin using them. Bacterial germination is also much faster during the summer time and in warmer climates, as heat is a factor that increases the cell division rate of these bacteria. As such, the expiry date should be shortened in the summer and in warm weather areas. As a rule of thumb, it is probably best to use a probiotic within the first three months of its encapsulation, and to purchase only refrigerated products, and then to refrigerate the product within one’s home as soon after the purchase as possible. Keep in mind that the use of prebiotics may be considered as a substitute for Probiotics. Prebiotic supplements can have their potency verified through third party analysis, and do not lose their potency over time in the fashion as do Probiotics (see Prebiotics in this document).
Finally, the first method of delivery, and likely the most effective delivery of Probiotics is through the intake of foods that contain live bacterial cultures, such as yogurt and other soured dairy products. (see the Am J Clin Nutr 2001, volume 73, supplement 2 edition, for more details on probiotic quality).
N.B. A 1990 study showed that most Probiotic supplements purchased in retail outlets contained no living bacteria at the time of purchase. Thus Prebiotic supplementation and soured dairy products may be a preferred method by which to modify the gut micro-flora.
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