Small Intestine

Aging has only minor effects on 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 intestinal motility, transit, permeability, or absorption. Although changes in small intestinal immune function occur, there is no evidence that these changes are clinically important.

Bacterial overgrowth in the small intestine, while unusual in healthy elderly people, is common among those with co-existing illness. Predisposing conditions include hypochlorhydria, small intestinal diverticula, and diabetes mellitus. Bacterial overgrowth may be asymptomatic or cause relatively nonspecific symptoms (eg, anorexia, weight loss) and may cause micronutrient malabsorption (eg, folate, Fe, Ca, vitamins K and B₆). Bacterial overgrowth is also a cause of diarrhea.

With aging, Ca absorption diminishes even in vitamin D-replete elders because of intestinal resistance to the action of 1,25-dihydroxyvitamin D. Vitamin D deficiency also contributes. Ca malabsorption is almost certainly a major factor in age-related bone loss in men and women; accordingly, the dietary Ca requirement is higher in the elderly.

This topic was last updated May 2005.