The Effect of Bacteria Modulation with Probiotic Consumption in Neurodegeneration During Aging: A Narrative Review of the Literature.

Aging is the result of the accumulation of a great variety of molecular and cellular damage over time. During aging, the brain undergoes changes and diseases such as depression, dementia, anxiety, Alzheimer's, delirium, behavioral disorders and aggression, and prolonged mourning, among others, appear. The gut-brain axis suggests that the gut and the brain have a bidirectional communication, so it is important to maintain proper intestinal health to strengthen the neurological changes of this age group. The intestinal microbiota is a dynamic and highly complex ecosystem of microorganisms residing in the gastrointestinal tract. The bidirectional and dynamic communication between the homeostatic systems, such as the endocrine and immune systems, as well as the nervous system, allow us to face problems associated with several diseases. Probiotics are defined as non-pathogenic live microorganisms that provide beneficial effects to the organism and participate in the prevention and treatment of diseases, which is the reason why it is important to promote interventions that keep intestinal microbiota in eubiosis (microbiota balance). The concentration and balance of the intestinal microbiota depend on several conditions, such as diet, antibiotic consumption, and lifestyle, to mentioned a few. However, interventions with probiotics have shown improvements in both cognitive function and processes that promote neurodegeneration. It is such that the research has been directed on designing strategies that improve not only oral bioavailability but also intestinal adhesion and retention, to clarify the frequency and dosage that should be consumed.