Probiotics in Irritable Bowel Syndrome - IBS
Irritable Bowel Syndrome is a widespread and multifactorial functional disorder of the digestive tract (114). It affects 8-22% of the population with a higher prevalence in women. It accounts for 20-50% of referrals to gastroenterology clinics and is characterized by abdominal pain, excessive flatus, variable bowel habit and abdominal bloating for which there is no evidence of detectable organic disease. Suggested etiologies include gut motility and psychological disorders as well as psycho-physiological phenomena and colonic fermentation (115).
A large proportion of patients have periods characterized by sudden and unforeseeable changes in the two main symptoms, constipation and diarrhea, even within a few days (115). It is very likely that the syndrome represents different groups of patients with probably different pathogenesis. Irritable bowel syndrome may follow gastroenteritis and may be associated with an abnormal gut flora and with food intolerance (117). The fecal microflora in some of these patients has been shown to be abnormal with higher numbers of facultative organisms and low numbers of lactobacilli and bifidobacteria (115).
Bacteria are the major component of formed stools and are influenced by substrates arriving with the ileal affluent. Stool production is related to quantitative and qualitative aspects of the colonic microflora and nearly 80% of the fecal dry weight consists of bacteria, 50% of which are viable.
Although there is no evidence of food allergy in irritable bowel syndrome, food intolerance has been identified and exclusion diets are beneficial to many of these patients. Food intolerance may be caused by an abnormal fermentation of food residues in the colon, as a result of disruption of the normal flora (115).
Some reports suggest that probiotics play a role in regulating the motility of the digestive tract (114). This may result in improvements in pain and flatulence in response to probiotic administration (115).
To assess whether preceding gastroenteritis or food intolerance were associated with colonic malfermentation, King et al. (117) conducted a crossover controlled trial with a standard diet and an exclusion diet matched for macronutrients in six female patients with irritable bowel syndrome and six female controls.
In this study fecal excretion of fat, nitrogen, starch, and nonstarch polysaccharide was measured during the last 72 hours of each diet. The total excretion of hydrogen and methane were collected over 24 hours in purpose-built 1.4 m3 whole body calorimeter. Breath hydrogen and methane excretion were measured for 3 hours after 20 g oral lactulose. The maximum rate of gas excretion was significantly greater in patients than in controls. The total gas production in patients was not greater than in controls, whereas hydrogen production was higher.
After lactulose, breath hydrogen was greater on the standard than on the exclusion diet. This means that colonic-gas production, particularly of hydrogen, is greater in patients with irritable bowel disease than in controls, and both symptoms and gas production are reduced by an exclusion diet. This reduction may be associated with alterations in the activity of hydrogen-consuming bacteria. It was therefore concluded that fermentation may be an important factor in the pathogenesis of this syndrome (117).
Spiller et al. (118) studied the intestinal permeability (Iactulose/mannitol ratio) and histological and immunological features in rectal biopsy specimens in 21 patients who had acute Campylobacter enteritis, 10 patients with postdysenteric irritable bowel syndrome and 12 asymptomatic controls. They found that the increased enteroendocrine cell counts, T lymphocytes, and gut permeability, which may survive for more than a year after Campylobacter enteritis, contribute to post-dysenteric irritable bowel syndrome (118), thus offering a rationale to use probiotics for several months after the infectious episode.
VSL3 in patients with Irritable Bowel Syndrome
The effect of the probiotics was studied by Brigidi et al. (119) in a clinical trial in which 10 patients suffering from this syndrome were administered the VSL#3 probiotic preparation. The results indicated that the administration of VSL#3 improved the clinical picture and changed the composition and biochemistry of fecal microbiota. The exact mechanisms of the positive effects are not known. The selection of patients may have had an important role in detecting the positive effects. Whether the induction of a significant increase in lactobacilli, bifidobacteria, and S. thermaphilus contributed to the regulation of the motility disorders or the increase in fecal B-galactosidase with a decrease in urease content indicate that a good response requires further study. The importance of this study is that it showed that the measurement of specific parameters and changes in the specific microflora was possible.
Kim et al. (120) investigated the effects of VSL#3 on gastrointestinal transit and symptoms of patients with Rome II-Irritable Bowel Syndrome with predominant diarrhea. Twenty-five patients with diarrhea-predominant Irritable Bowel Syndrome were randomly assigned to receive VSL3 powder (450 billion lyophilized bacteria/day) or matching placebo twice daily for 8 weeks after a 2-week run-in period.
Pre- and post-treatment gastro-intestinal transit measurements were performed in all patients. The patients recorded their bowel function and symptoms daily in a diary during the 10-week study, which was powered to detect a 50% change in the primary colonic transit endpoint. There were no significant differences in mean gastrointestinal transit measurements, bowel function scores or satisfactory global symptom relief between the two treatment groups, pre- or post-therapy.
The differences in abdominal bloating scores between treatments were borderline significant. Abdominal bloating was reduced with VSL3, but not with placebo. Furthermore, VSL#3 had no effects on individual symptoms such as abdominal pain, gas and urgency. VSL3 was well tolerated by all patients, and thus it seems to relieve the abdominal bloating in patients with diarrhea-predominant Irritable Bowel Syndrome (120).