Define colonization of the gut - probiotic effect?

It is not clear how probiotics influence the flora and produce a beneficial effect. However, colonization of the gut appears to be a prerequisite for the probiotic effect. Important relevant features may be:

- Resistance to low pH and bile acids, and

- Ability to adhere to intestinal epithelium.

However, ability to adhere to intestinal epithelium does not ensure that an organism will permanently colonize the gut. Also, there is a continuous interchange of species with one strain being replaced by another, which is possibly better suited. Since some strains are more suitable than others. Organisms such as Saccharomyces boulardii are effective although they do not grow in the gut. For such organisms, continuous administration is required to ensure the presence of large numbers of metabolizing cells in the GIT. As a dietician, you must be now curious to know which foods contain probiotics.