Recently,
the term prebiotics was introduced. Certain oligo-saccharides (e.g. inulin, fructo- and galactooligo-saccharides) have the capability to be selectively metabolized by gut bacteria resulting in improved gastrointestinal functions. Up to now this concept is not studied adequately for EN. For clinical reasons, the classifications according to the phy-siological properties would be more useful but physiological effects are not always easy to measure