[Characteristics of disease and involution-induced changes in intestinal absorption]

With advancing age functional and morphological changes take place within the intestinal tract. The absorption rate (constant k12), the time of appearance of the relative maximum of the D-xylose concentrations in the blood serum after oral administration (time tm), and especially the extent of the relative absorption in the small intestine until the time tm RR (tm) determined by graphic-mathematical evaluation of the blood levels kinetics of D-xylose after oral and intravenous administration, are useful parameters for differentiation between involutively and pathological changes in intestinal absorption. Absorption disorders in old age are due to morbidity and not, sui generis, to involution.