Can nutritional strategies improve the microbiome and health status at the advanced age?

Abstract

The microbial community inhabiting our body is known as ‘microbiota’, and the ensemble of their genomes is named as ‘microbiome’. The gut, and more particularly the colon, is the most densely populated area of our body. The gut microbiota and its metabolites interact with the host at different levels, its correct composition and functionality being essential for maintaining a ‘healthy status’. The recent development of next generation sequencing (NGS) methods has greatly facilitated the study of the microbiota and has evidenced that its composition is strongly influenced by age and diet, although some aspects of its functionality still remain insufficiently known. On the other hand, the precise way in which the diet and its components modify the functionality of the intestinal microbiome is far from being completely understood. Changes in the intestinal microbiota occur during ageing and are frequently accompanied by physiological changes, modifications of the functionality of the gastrointestinal tract, impairment of the immune system (‘inflammaging’), and variation in dietary habits that frequently lead to nutritional deficiencies or malnutrition. All these alterations considered together may contribute to the higher susceptibility of elderly people to disease. There are a limited number of studies describing the composition of the microbiota in elderly individuals, and even less about its functionality. It is known that the core microbiota of the elderly significantly differs from that of healthy adults. Not all changes in the microbiota as age advances may necessarily mean a detrimental health effect, as functional redundancy exists in this ecosystem. However, the reduction in species diversity of most bacterial groups, shift in dominant species, increase of facultative anaerobic bacteria, and decrease in the production of short chain fatty acids in the gut are general features that impair the microbiota resilience, and contribute to the establishment of a state prone to disease and to the increase of infections risk in the elderly. To design nutritional interventions for this specific human group, it is necessary to establish the precise action targets by comparing the microbiota of defined elderly populations with healthy subjects from their near surroundings; these should be at preference adults from a socio-economic group with historic past, social habits and geographical location as close as possible to the elder population under study. Understanding the mechanisms underlying the interaction of specific nutrients with the microbiota, as well as the beneficial action of probiotics, prebiotics and bioactive dietary compounds will provide the scientific support for the rational design of specific diets and food products for the elderly population.