probiotics, prebiotics and the gut microbiota - International Life ...

18 Concise Monograph Seriesbacteria can initiate and/or exacerbate inflammatorybowel conditions. CD and UC may thus result from aninappropriate mucosal immune response to the GImicrobiota in genetically susceptible individuals. There isalso some evidence from clinical studies that the balanceof different groups of commensal bacteria might bealtered in IBD patients.Numerous studies of both probiotics and prebioticsin animal models have shown a positive impact on theprevention or treatment of IBD. Clinical studies in CDsubjects have not been effective in prolonging remissionof CD, but there are promising data indicating thatsome probiotics are useful in maintaining remission inUC. In another inflammatory bowel condition known aspouchitis, which can occur after surgery to treat UC, onemixture of probiotic strains appeared to be effective inhelping maintain remission. The potential for prebioticsand synbiotics to help the management of IBD has beenshown in several small studies with fructans, mainly in thereduction of inflammatory markers, but as yet the datado not allow a final conclusion. Although there are stillinsufficient data to draw firm conclusions on the effect ofpre- or probiotics on IBD, importantly, none of the trialsconducted thus far have raised concerns regarding theirsafety in patients with IBD at the levels of intake tested.Irritable bowel syndromeIrritable bowel syndrome (IBS) is a distressing conditionthat is characterised by an array of symptoms such asabdominal pain, bloating and altered bowel habits thatmay often alternate between constipation and diarrhoea.As similar symptoms can be observed from time to time inthe general population, a specific set of criteria (known asthe Rome criteria) was developed to improve consistencyof diagnosis of IBS. In industrialised countries, IBS affectsbetween about 5 and 20% of the adult population, withrates higher in women and older people. Recently, therehas been interest in the role of inflammatory processes asa potential cause of IBS. In addition, in a certain subset ofsubjects, it appears that previous gut infections play a rolein onset of IBS (post-infectious IBS). Furthermore, in somestudies, lower levels of bifidobacteria have been observedin subjects with IBS compared with healthy subjects.Because of the lack of good therapy for IBS and theidentification of abnormal microbiota in IBS subjects, bothprobiotics and prebiotics have been investigated for theirability to help subjects manage this condition. A coupleof probiotic preparations have been shown to providereduction in a global symptom score (the sum of a numberof different symptom scores) and in reducing abdominalpain; however, no change in diarrhoea, constipation orbloating was confirmed. In other studies, some strainshad no effect or resulted in worsening of symptoms. Forsome prebiotics, studies showed that low doses led toan improvement in the condition, whereas a larger loadled to an enhancement of the perceived symptoms.Thus, additional research will be required to determine ifconsistent benefits can be observed by those experiencingIBS if they use prebiotics and probiotics.Impact on the GI tract specific toprebioticsColon cancerColon cancer has been linked to diets low in dietary fibreand thus the potential for prebiotics to reduce coloncancer risk has also been investigated, mainly usingin vitro techniques and animal models. Results fromanimal studies with endpoints such as DNA damage,aberrant crypt foci as well as tumours in the colonsuggest that prebiotics may reduce the risk of coloncancer. This is supported by ample in vitro evidence.Synbiotics were investigated in a few animal studies andwere found to be more effective than either prebioticsor probiotics alone. One synbiotic study (SYNCAN