Most conventional forms of drug therapy suppress or modify the host immunoi
nflammatory response and neglect the other contributor to disease pathogene
sis-the environmental microflora. Probiotics are live microbial food ingred
ients that alter the enteric microflora and have a beneficial effect on hea
lth. The rationale for using probiotics in IBD is mainly based on evidence
from human studies and experimental animal models implicating intestinal ba
cteria in the pathogenesis of these disorders. The relationship between bac
teria and intestinal inflammation is complex and does not appear to reflect
a simple cause and effect. Similarly, the field of probiotics is complex a
nd in need of rigorous research. Until the indigenous flora are better char
acterized and mechanisms of probiotic action defined, the promise of probio
tics in IBD is unlikely to be fulfilled. Because of strain-specific variabi
lity and clinical and therapeutic heterogeneity within Crohn's disease and
ulcerative colitis, it cannot be assumed that a given probiotic is equally
suitable for all individuals. Although preliminary results of probiotic the
rapy in animal models and humans with ulcerative colitis and pouchitis have
been encouraging, their efficacy in treatment or maintenance of remission
of Crohn's disease remains to be clarified. However, the circumstantial evi
dence for some form of biotherapeutic modification of the enteric flora in
Crohn's disease seems compelling. In the future, probiotics may offer a sim
ple adjunct to conventional therapy with the emphasis on diet shifting from
one of nutritional replenishment alone to a more functional role.