Intestinal bacteria and ageing

Abstract

Summary Advancements in science and medicine, as well as improved living standards, have led to a steady increase in life expectancy, and subsequently a rise in the elderly population. The intestinal microbiota is important for maintenance of host health, providing energy, nutrients and protection against invading organisms. Although the colonic microbiota is relatively stable throughout adult life, age‐related changes in the gastrointestinal (GI) tract, as well as changes in diet and host immune system reactivity, inevitably affect population composition. Recent studies indicate shifts in the composition of the intestinal microbiota, which may lead to detrimental effects for the elderly host. Increased numbers of facultative anaerobes, in conjunction with a decrease in beneficial organisms such as the anaerobic lactobacilli and bifidobacteria, amongst other anaerobes, have been reported. These changes, along with a general reduction in species diversity in most bacterial groups, and changes to diet and digestive physiology such as intestinal transit time, may result in increased putrefaction in the colon and a greater susceptibility to disease. Therapeutic strategies to counteract these changes have been suggested in ageing people. These include dietary supplements containing prebiotics, probiotics and a combination of both of these, synbiotics. Limited feeding trials show promising results with these supplements, although further longer‐term investigations are required to substantiate their use in elderly healthcare fields.

Nutrition and the gut microbiome in the elderly

“…With regard to other relevant intestinal microbial populations such as the phylum Bacteriodetes, the results are more variable, with some studies reporting lower levels 19,[23][24][25][26][27] while others have indicated increases of this microbial group in elderly subjects. 21 Similarly, variable results have also been observed for lactobacilli, with some studies reporting a reduction 22,28 and others an increase in the levels of these microorganisms at older ages. 24,27,29 It is still unclear whether this variability in the results obtained for certain microbial groups is related to actual population differences or to methodological issues, such as the different techniques used for determining microbial abundancies ( Table 1).…”

The bifidogenic effect of inulin and oligofructose and its consequences for gut health

“…In elderly persons, the content of bifidobacteria decreases, whereas that of enterobacteria and clostridia increases (Hopkins and MacFarlane, 2002;Woodmansey, 2007). It might, therefore, be expected that in elderly, the bifidogenic effects of inulin could be more pronounced.…”

Composition, variability, and temporal stability of the intestinal microbiota of the elderly

“…The gut microbiota composition of elderly subjects is expected to be in a state of flux, a theory supported by culture-dependent methods (29). More recent studies have suggested that the Bacteroides species diversity was marginally increased in the feces of elderly subjects and that of bifidobacteria reduced (30), whereas a further study suggested that both Bacteroides numbers and species diversity decline in the elderly (31,32). The proportions of the phyla Firmicutes, Bacteroidetes, and Proteobacteria were 58%, 15%, and 27%, respectively (33) in three elderly subjects in Japan, using 16S rRNA gene-clone library sequencing.…”