A wide range of health effects, including enhanced metabolism of dietary compounds, alleviation of disturbed bowel functions, improved resilience of the gastrointestinal (GI) microbiota, resistance against infections within and outside the GI tract, and prevention of allergies, have been linked with the use of specific (combinations of) probiotic microbes. The findings are based on the potential etiological role of the gut microbiota in the pathogenesis of a number of clinical conditions and in the modulation of host immune functions, providing means for modulating the host immune responses both locally and systemically. The proposed and documented GI benefits of the probiotics are based on several clinical intervention studies with varying quality and methodology and on meta-analyses of the aforementioned (Table 25.1). This chapter will discuss the outcomes of probiotic intervention studies on GI disorders and diseases.410 411