Aging is associated with a modest slowing of gastric emptying, which may predispose to anorexia and weight loss by prolonging gastric distention and increasing meal-induced fullness and satiety. Small Intestine Aging has only minor effects on the structure of the small intestine, with some alteration in villus architecture and a reduction in the neuronal content of the myenteric plexus. Aging does not result in major changes in small-intestine motility, transit, permeability, or absorption. Although changes in small-intestine immune function occur, there is no evidence that these changes are clinically important. Predisposing conditions include hypochlorhydria, diverticulosis, and diabetes mellitus.
Bacterial overgrowth is also a cause of diarrhea in the elderly.
With age, calcium absorption diminishes, even in healthy persons who are vitamin D replete. In such cases, the reduction appears to be due to intestinal resistance to the action of 1,25-dihydroxyvitamin D, not to a reduction in the plasma concentrations of this hormone. Vitamin D deficiency also occurs often in the elderly and is associated with malabsorption of calcium. Large Intestine Aging does not appear to be associated with major changes in colonic or anorectal motility. Rectal compliance and tone are normal, but the perception of anorectal distention is reduced in the elderly.