KEYWORDS: microbiota; dietary modulation; dietary intervention; healthy ageing; dysbiosis
ABSTRACT: The human intestinal microbiota has defined health-promoting properties. Alterations in the composition of the microbiota have been linked to common health problems, particularly at dynamic life stages such as older age. Environmental conditions, including diet, shape the composition of the intestinal microbiota. Recent studies have begun to link dietary intake with distinct microbiota compositional profiles and to link these profiles with health parameters in older populations. Defining the role of diet in supporting health-promoting microbiota profiles provides the foundation for the development of dietary interventions specifically targeted at sustaining health in older age.
THE HUMAN GUT MICRIOBIOTA: ITS ROLE AND ITS POTENTIAL
The total collection of microbes that naturally exist in the gut of an individual (the microbiota) contains trillions of bacteria – approximately tenfold more than the 1014 human cells in the body (1). The microbiota is unique, remarkably diverse and stable over defined periods of time (1, 2), with older adults displaying greater inter-individual variation than that of younger adults (2). The human gut microbiota has a close symbiotic relationship with its host and conveys essential benefits; it extracts energy from the diet, produces nutrients, regulates the stress response, protects against attack by other organisms and both primes and modulates the immune system (3, 4). In addition, the collective genetic information of the gut microbiota (the microbiome), contains over 100 times the number of genes in the human genome and provides increased physiological abilities (5).
The availability of improved, and constantly improving, culture-independent, sequencing and bioinformatics technologies to interrogate the complexity of the microbiota has driven efforts to understand its role in promoting and maintaining health, particularly in populations at dynamic life stages such as the very young and older adults. Such technological advances allow for greater numbers of subjects to be examined in ever-greater depth, providing increasingly valuable information as to the composition and function of the human gut microbiota and its influence on health. Characterising the fundamental compositional microbiota profile of healthy individuals will allow for the identification of those detrimental differences associated with disease, thus offering the potential to predict disease and/or disease progression. It will provide the basis for the development of modulatory regimes with the potential to mitigate disease progression and maintain or return the microbiota to a health-promoting state.
THE MICROBIOTA AND AGEING
The development of the dynamic infant gut microbiota to that of a stable adult profile is influenced by maternal, dietary and environmental factors (6, 7). Evolution of the infant gut microbiota composition towards an adult-like composition has been found to occur within the first three years of life across diverse geographical and socioeconomic populations (8). The total number of bacterial species in the adult gut microbiota has been reported at >1,000 distinct groups, of which Firmicutes and Bacteroidetes dominate (>90%) and Actinobacteria and Proteobacteria constitute...