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Hanaway reports that Cordain 9 describes the dietary patterns most common today, and compares them with the characteristics of ancestral diets. He notes alterations in:
all of which have tremendous effects on the balance of the commensal* flora within the gastrointestinal tract.
The critical functions of the commensal* flora are:
New evidence is evolving that the persistent interactions between host and bacteria that take place in the gut may constantly reshape the immune system10.
He says that clinicians see the profound effects of altered commensal* flora in the nearly 15% of the population who are affected by the functional GI disorder, Irritable Bowel Syndrome - (IBS) 11. It is also becoming clear that the immune dysregulation of Crohns Disease and Ulcerative Colitis - (IBD) - is profoundly influenced by the role of gut flora12. This includes symptomatic evaluation of patients who have alterations in bowel patterns defined by the Rome II Criteria meet the definition of Irritable Bowel Syndrome (IBS)13.
Irritable Bowel Syndrome - IBS - Rome II criteria:
12 or more weeks of continuous or recurrent abdominal pain or discomfort, plus at least 2 of the following:
Hanaway says that studies have demonstrated the alteration in commensal* flora present in Irritable Bowel Syndrome - IBS - in both colonic biopsy samples 14 and stool analysis15. There is considerable research on optimal methodology for evaluating gut flora.
Dysbiosis can be measured by stool analysis and culture, but 99% of colonic flora are what he describes as 'facultative anaerobes' and so only about 50% will be picked up by culture methods. Hanaway explains that decrease or absence of normal Lactobacillus, Bifidobacter and E coli species in stool culture is an indication of imbalance16.
Recent studies on the pathogenesis of Irritable Bowel Syndrome - IBS - have evaluated the common association with small bowel bacterial overgrowth (SBBO), also known as bacterial overgrowth of the small intestine (BOSI) and small intestinal bacterial overgrowth (SIBO). SBBO is noted when the coliform and anaerobic bacteria from the large intestine produce deleterious effects within the delicate environment of the small intestine.
A simple breath test is performed by measuring hydrogen and methane gas produced after oral administration of lactulose. As gut bacteria ferment the lactulose, the gas production increases. Typically, the gas production will increase when the fermentable substrate has passed into the large intestine, but patients with SBBO have this increase in gas production much earlier.
Intestinal dysbiosis has been noted to be present in 78% of Irritable Bowel Syndrome - IBS - patients who tested positive for SBBO. Studies have recently begun to evaluate probiotic therapy to improve the rate of SBBO.
It is well recognized that several other chronic diseases have a high degree of overlap with Irritable Bowel Syndrome - IBS - including fibromyalgia, interstitial cystitis, and chronic fatigue syndrome17.
Studies in patients with fibromyalgia have shown that 100%18 and 77%19 of patients also have SBBO. It has been postulated that the immune response to bacterial antigens present in the small intestine provides a framework for understanding the hypersensitivity present in both Irritable Bowel Syndrome - IBS - and fibromyalgia20.
So, says Hanaway, we begin to see that alteration in the distribution of gut flora is associated with clinical syndromes outside of the gastro-intestinal tract. He says it is useful and important to modulate the gut flora for improved health by supplementing the diet with prebiotics and probiotics.
The word probiotic (derived from the Greek and meaning "for life") was first used in 1965 to describe a function that is opposite to that of antibiotics. It has subsequently been defined as "a preparation of or a product containing viable, defined microorganisms in sufficient number, which alter the microflora (by implantation or colonization) in a compartment of the host and by that exert beneficial health effects on the host" 21.
A probiotic must:
Other common desirable properties include being able to produce antimicrobial substances, modulate immune responses, and influence human metabolic activities.
A prebiotic has been defined as " a non-digestible food ingredient which beneficially affects the host by selectively stimulating the growth of and/or activating the metabolism of one (or more) health-promoting bacteria in the intestinal tract, thus improving the host's intestinal balance" 23.
Prebiotics induce antimicrobial effects via their selective stimulation of commensal strains that modulate immune function and compete with pathogens for receptors.
The most common probiotic bacteria are:
Probiotic supplementation has been shown to be beneficial in:
Recently, researchers have also demonstrated the beneficial effect of probiotics for improving symptoms in Irritable Bowel Syndrome (IBS)28 and for normalizing imbalances with inflammatory cytokine ratios29. Probiotics are moving into the mainstream of treatment options for Irritable Bowel Syndrome (IBS), as well as Crohns and Ulcerative colitis - i.e. Inflammatory Bowel Disease (IBD)30. He explains that disease-specific activity and modulation of the immune system are 'bacterial species' and 'subspecies-dependent' processes. Therefore, the overall community of bacterial flora becomes a critical determining factor for promoting health and preventing and/or treating disease.
In addition to the benefit of probiotic therapies in Irritable Bowel Syndrome - IBS - as well as Crohns and Ulcerative Colitis - i.e. Inflammatory Bowel Disease (IBD,) additional studies have successfully used probiotics as a preventive strategy for infants at risk for atopic illness. Based upon the immunologic imbalance of T-helper cells offered in the hygiene hypothesis, researchers in Finland gave probiotics to infants with a family history of atopic illness and demonstrated a 50% reduction in incidence31.
A follow-up study at four years confirmed these findings32. Isolauri and her colleagues showed that the anti-allergenic and anti-inflammatory activity of supplemental probiotics was mediated, at least in part, by a decrease in intestinal permeability33. These findings have been confirmed in children with moderate to severe atopic dermatitis, with the improvement in intestinal permeability correlating with improvements in the severity of eczema34.
The innate immune system discriminates between potential pathogens and commensal* bacteria by using a number of pattern-recognition receptors (PRRs). Mammalian cells express a series of toll-like receptors (TLRs) that recognize bacterial and microbial structures, including DNA35.
When infection or pathogens are present, the inflammatory response can increase intestinal permeability. This allows for increased sampling of gut flora by the immune system-a physiologic process of checks and balances. In the presence of an alteration of the gut flora, immune dysregulation, or a genetic predisposition, there is a sustained chronic inflammation and release of calprotectin from neutrophils36.
Conversely, the presence of healthy commensal flora and/or probiotics has been shown to have an anti-inflammatory effect on the gastro-intestinal epithelium37.
*Commensal: Living in a relationship in which one organism derives food or other benefits from another organism without hurting or helping it. Commensal bacteria are part of the normal flora in the mouth.