SUMMARY Using the combined results of oral and intravenous xylose tests, it is demonstrated that 26% of a group of geriatric patients absorb from the small bowel less efficiently than younger subjects.The method used excludes poor renal function and incomplete bladder emptying as possible causes for the differences found between the two age groups. Altered gastric emptying is also excluded as a possible factor. Phillips and Gilder (1940) reported reduced absorption of dextrose in aged rats when direct measurements were made on luminal residues after an oral load. In man, Meyer, Sorter, Oliver, and Necheles (1943) were probably the first workers to present evidence suggestive of impaired small bowel function in the elderly in relation to theabsorptionofmonosaccharides. Their findings were based on the results of observing blood galactose levels in elderly subjects after oral ingestion of galactose. Although slow removal of galactose from the subjects' blood could account for the differences between their young and elderly groups, the initial low levels found only in the elderly could have been caused by the impaired absorption of the monosaccharide.Guth (1968), using similar reasoning to Meyer et al, concluded from the xylose tests that he performed that small bowel absorption was impaired in the elderly. (However, both groups' conclusion can be criticized, as impaired renal function was not actively excluded and could therefore be influencing their results.) Davies and Shock (1950), Dontas (1963), and Friedman, Raizner, Rosen, Solomon, and Sy (1972 all clearly demonstrated by different methods the frequency of renal functional impairment with increasing age.Sapp, Seasions, and Rose (1964) and Fikry and Aboul-Wafa (1965) attempted to exclude elderly subjects with subnormal renal function from their studies on the effects of age on the standard xylose test, and found a decrease in urinary recovery of the substance after an oral dose.

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