Prebiotics and probiotics in ulcerative colitis: where do we stand?

or VSL#3 [5–8] . The latter contains 8 different strains of lactobacillae and bifidobacteriae. E. coli Nissle is probably the best explored probiotic preparation for the treatment of UC patients [9] . Other bacterial species are less well explored. In addition, the combination of a probiotic together with a prebiotic substance (a so-called symbiotic preparation) has rarely been studied [10] . Therapy with E. coli Nissle for maintenance of remission of UC is now recommended in several European guidelines on the treatment of UC [11] . In this issue of Digestion, Ishikawa and co-workers investigated the effect of bifidobacteria in patients with ulcerative colitis (Beneficial Effects of Probiotic Bifidobacterium and Galacto-oligosaccharide in Patients with Ulcerative Colitis: A Randomized Controlled Study). They had previously found that bifidobacteria-fermented milk containing live Bifidobacterium was effective in maintaining remission in UC patients and also in treating patients with mild to moderately active UC [12] . The latter study was a randomized placebo-controlled trial. However, such bifidobacteria-fermented milk not only contains live bacteria but also their metabolic products, making it difficult to decide whether the bacteria itself is anti-inflammatory or whether these metabolic products can downregulate inflammation. This illustrates another difficulty in pre-/ pro-/synbiotic studies: it remains unclear whether the live bacteria are necessary for a clinical effect of metabolic The human gastrointestinal tract is occupied by a complex and abundant microbial community accounting for as many as 10 13 –10 14 microorganisms in the colon. This microbiota participates in a symbiotic relationship with their eukaryotic host and this partnership is viewed as essential for maintaining homeostasis. The coexistence of the host with its intestinal micriobiota is tightly controlled at various levels and an accumulating body of evidence suggests that the failure of this homeostasis is an important contribution to disease development in inflammatory bowel disease such as ulcerative colitis (UC) [1, 2] . According to a recent survey, 2 out of 5 patients with inflammatory bowel disease use probiotics regularly [3] , therefore it is most mandatory to evaluate the potential efficacy of preand probiotics in UC. A recent meta-analysis by Zigra et al. [4] found 9 studies on the effects of probiotics acceptable for further analysis in the field of UC. The analyzed studies were very heterogeneous in concept and methodology. Consecutively, the results also vary among those trials. The improvement in UC activity, induction of remission and the frequency of adverse effects did not differ significantly between probiotictreated groups and control patients mainly treated with 5-aminosalicylic acid preparations [4] . Specific probiotic products have been established for the treatment of UC, such as Escherichia coli Nissle 1917 Published online: April 15, 2011