The gut microbiome changes with age in ways that are not favorable to health. Microbes that provoke inflammation and tissue dysfunction grow in number, replacing those microbes that generate beneficial metabolites. There are many plausible contributions to this process of change, and as is usually the case for anything to do with aging, it is hard to determine which are more or less important than the others. This is particularly the case here, as studies suggest that meaningful change in the composition of the gut microbiome begins as early as the mid-30s, a point in adult life at which very little is concretely known regarding which mechanisms of aging are dominant.
The authors of today's open access paper surveyed the literature to identify human studies that report specific differences in gut microbiome composition between various groups at different ages. Some of the studies specifically included long-lived populations such as centenarians. If interested in the results, skip ahead to table 2, which lists microbial taxons found to be increased or decreased with age, or in long-lived populations. A fair number of studies are listed, and some commonalities emerge.
This sort of data, taken in the aggregate, will form the basis for later efforts to favorably adjust the composition of the gut microbiome in specific ways in order to slow or reverse aspects of aging and age-related disease. Altering the composition of the gut microbiome can at present be achieved temporarily via probiotics, with some degree of control over the outcome, or permanently via approaches such as fecal microbiota transplantation, but with little control over the specifics of the outcome. It is to be hoped that future approaches can combine permanence of the changes following a single treatment with good control over the resulting mix of populations.
Gut microbiome and healthy ageing: a systematic review of literature
The gut microbiota comprises a diverse community of micro-organisms, including bacteria, archaea, viruses, parasites, and fungi, which inhabit the large intestine. These microbes play a crucial role in various physiological processes, including facilitating digestion, modulating immune responses, protecting against pathogens and synthesizing neurotransmitters and essential metabolites, such as vitamins, amino acids, secondary bile acids and short-chain fatty acids (SCFAs).
In 2023, researchers expanded the hallmarks of ageing framework by introducing three additional hallmarks, one of which is gut microbiome dysbiosis. This condition is characterized by reduced microbial diversity and an increased abundance of pro-inflammatory species. However, in the context of healthy ageing, the gut microbiome tends to maintain relative stability and contributes to systemic homeostasis. Studies have shown that the gut microbiome undergoes physiological changes throughout the ageing process. However, the direction and magnitude of these changes, including shifts in microbial diversity, are highly variable. These changes depend on several factors such as health status, diet, lifestyle, medication use, and population cohort. Microbial alterations often reflect a transition from a diverse and stable adult microbiome to a less balanced state in later life, marked by increased inflammation, reduced production of beneficial metabolites and disrupted immune function, changes that may contribute to the progression of age-related diseases
This systematic review aimed to identify compositional and functional features of the gut microbiome associated with healthy ageing. A total of 41 studies met the eligibility criteria and were included in this review. The included studies represented several regions, including recognized longevity hotspots, although geographic representation remained limited. Most studies used 16S rRNA gene sequencing (n=24; 58.5%), followed by shotgun metagenomics (n=13; 31.7%), both (n=3; 7.4%) or metaproteomics (n=1; 2.4%). Enrichment of specific taxa such as Akkermansia, Alistipes, and Parabacteroides was consistently reported in centenarians, alongside distinct patterns in older adults and long-lived individuals. Functional profiling suggested differences in pathways related to amino acid catabolism, vitamin biosynthesis, and pathways potentially linked to immune modulation, inflammatory processes, and gut barrier support.
View the full article at FightAging
