There is a growing interest in the manipulation of the gut microbiome. Changes in the balance of microbial populations occur with age, leading to an increase in harmful, inflammatory species at the expense of species that produce beneficial metabolites. Animal studies have demonstrated that even radical changes in the microbiome from a one-time procedure, such as that produced by fecal microbiota transplant from a young individual, can be sustained over time, rejuvenating the balance of microbial populations and improving health as a result. As yet there seems to be little enthusiasm or funding to run clinical trials in older people, however, despite the sizable benefits produced in animal models.
Far from being a static entity, the gut microbiome (GM) suffers various modifications during different life stages of the individual. The transformation of these biocommunities in older adults is particularly evident after considering that when a person reaches an advanced age, they have been exposed to different environmental factors over an extended period. Multiple studies that analysed GM compositions from people of advanced age concluded that there is a general decrease in microorganism diversity and probiotics, together with an increase in opportunistic agents that could be related to age-related chronic diseases. Although the modifications vary according to the specific age group, numerous studies that found differences in the GM composition of elderly groups (ages 99-80 and 79-60) agree on the predominance of the phyla Bacteriodetes and Firmicutes, the first one being more prevalent in the elderly than in younger adults where the phylum Firmicutes is more abundant.
Similarly, studies have also found decreases in several bacterial groups, including Actinobacteria, certain Ruminococcaceae and Bacteroidaceae members, and Bifidobacterium, Faecalibacterium, Eubacterium, Bacteroides, Clostridium, and Oscillospiraceae genera. In addition, numerous microorganisms, mainly opportunistic pathogens and those related to chronic inflammation, increase during ageing.
In recent years, scientific evidence has shown the possibility of delaying ageing by manipulating the regulatory pathways involved in its bidirectional relationship with the GM. It is known that there is a relationship between intestinal dysbiosis and multiple age-related diseases, such as inflammatory bowel disease and musculoskeletal diseases and neurological conditions. Nevertheless, there are beneficial bacteria that, rather than deleterious consequences of ageing, may contribute to homeostasis maintenance and healthy ageing. In this respect, prebiotics, probiotics, a healthy diet, regular physical activity, and drugs have gained scientific interest in microbial activity regulation.