ABSTRACT
Aging affects the gastrointestinal (GI) tract in many ways. The aging-associated physiological changes inuence the GI tract microbiota both directly and indirectly. First, physiological changes affecting a person’s eating behavior include increased taste and smell thresholds, decreased muscle strength for chewing, and loss of teeth, which all can lead to a very selective consumption of foods and consequently to an altered nutritional status or even to malnutrition. Further, difculties in swallowing may narrow the range of consumed products. In addition, hypochlorhydria due to atrophic gastritis or due to use of proton pump inhibitors or H2-antagonists
CONTENTS
16.1 Gut Function and Microbiota of Elderly Individuals .................................... 341 16.1.1 Aging and Gastrointestinal Tract Function ....................................... 341 16.1.2 Assessment of Microbiota ................................................................. 342 16.1.3 Aging and Gut Microbiota ................................................................ 343
16.2 Probiotics and Prebiotics for Elderly Individuals.......................................... 345 16.2.1 Probiotics and Prebiotics ................................................................... 345 16.2.2 Efcacy of Probiotics ........................................................................ 345 16.2.3 Efcacy of Prebiotics ........................................................................348 16.2.4 Synbiotics .......................................................................................... 350
16.3 Summary and Concluding Remarks ............................................................. 350 References .............................................................................................................. 351
is common among elderly people and may lead to small intestinal bacterial overgrowth, chronic diarrhea, and malabsortion.1,2 Atrophic gastritis may also affect the bioavailability of calcium, ferric iron, and vitamin B12 and contribute to the de- ciency of these minerals and vitamins. Also colonic transit may slow with aging, but the individual variation is high. Constipation, which is a common symptom in elderly people, may be partly explained by the decreased intestinal motility. Another factor linked with constipation is low fecal weight, which has been reported among the elderly people. The slow intestinal transit has been associated also with increased bacterial putrefaction and, consequently, increased levels of ammonia and phenols in the gut. The immune system is often adversely affected by the aging process and the resistance to diseases may be decreased. More detailed description about the aging-related physiological and functional changes in the GI tract can be found elsewhere.3,4 The microbiological changes in the GI tract due to aging have been characterized and are discussed in detail below after the short introduction on modern microbiota assessment techniques. Further in this chapter, we discuss the possibilities of counteracting the aging-associated changes in the GI tract with probiotics and prebiotics. There is experimental and clinical evidence that they may support antibacterial and barrier-enhancing actions, have antiinammatory effects, as well as enhance immunity.5,6
16.1.2 Assessment of Microbiota
The knowledge on intestinal microbiota has been gained over the years by using various microbiological techniques. Although early studies relied entirely on cultivation, today molecular biological techniques complement the culturing techniques and also allow us to study the microbiota in a culture-independent way.7
