In a recent review published in Current Opinion in Microbiology, researchers reviewed existing data on variations in human microbiota, emphasizing on ageing- and ethnicity-associated changes in the microbiota.
Human microbial heterogeneity lays the foundation for precision therapeutics, and thus, the potential of personalized microbiota-based diagnostic and therapeutic strategies can be tapped fully by understanding human microbial variations. However, the factors associated with alterations in the human microbiome have yet to be well-characterized.
Further, most of the human microbiota data has been obtained from residents of westernized and socioeconomically developed nations, with the probable skewing of microbiota variations and their associations with health. Moreover, the under-sampling of ethnic minorities in microbiota analyses must be addressed for assessing the history, context, and evolving dynamics of the human microbiota in the context of disease risks.
About the review
In the present review, researchers highlighted recent advances in characterizing human microbiota variations associated with ageing and various ethnicities globally.
Age-related changes in the microbiota of humans
Factors that shape the human microbiota include birth type, family sizes, cohabitation, housing, domestic animals, age, sex, physical fitness, diet, antibiotics, non-antibiotic drugs, and alcohol intake. At the societal level, complex associations of health inequalities, socioeconomic status, and social networks with the human microbiome balance have been reported.
Studies have demonstrated an inverse association between the microbiota and an individual’s age, and conversely, microbial compositional variations contribute to the process of ageing and age-associated diseases. All individuals do not age uniformly, and the differential ageing rates reflect in the human microbiota. Therefore, the human microbiota abundance is evolving as a biomarker to evaluate differences in the biological age and chronological age and between health and disease. Human microbiomes lacking Bacteroides species have been strongly associated with a healthy type of ageing.
Other factors related to variations in the human microbiota composition
Mediterranean diets, involving reduced intake of saturated-type fats, red meat, and milk products, with high consumption of fruits, vegetables, fish, legumes, nuts, and olive oil, have been reported to reverse age-associated microbiota alterations and delay cognitive decline. Studies have reported the co-evolution of human beings and intestinal microbes, with notable variations in Helicobacter pylori diversity associated with human migration.
Microbiome compositions vary among individuals residing in industrialized or non-industrialized regions. Non-industrialized region-associated microbiomes or ancestral microbes have adapted to metabolizing complex-type carbohydrates from diets with high fibre content. The microbial compositions vary by season, climatic fluctuations, and accessibility to unprocessed-type foods. The microbiome of individuals living in non-industrialized regions reportedly has lower Bacteroides/Prevotella spp. ratio, elevated counts of Treponema species, and varying abundance of parasites that affect the immunity of the host.
Naturally maintained palaeofaeces microbiome genomes resemble the genomes of non-industrialized human intestinal microbiota. Socioeconomic developments and industrialization have been associated with microbiome diversity losses, lowered parasitism, reduced counts of ancestral microbes like Helicobacter pylori species and elevated counts of microbes associated with non-communicable and chronic metabolic and inflammatory diseases.
Immigration has been related to an increased abundance of microbes associated with obesity. A study on Irish travellers reported three key factors influencing the human microbiota composition, i.e., living conditions, closeness to domestic pets during childhood and family sizes, with the average number of siblings among traveller families and other families being 10, and one, respectively).
Based on the review findings, the human microbiome is influenced by age, diet, ethnicity and immigration. Further research is required to improve understanding of age-related microbiome changes to identify targets and develop tailored microbiota-based therapeutic interventions. The increase or decrease in microbial abundance associated with changes in dietary patterns and modernization needs to be assessed further to develop highly specific precision medicine catered to the residential locations and food consumed.
The co-diversification of microbes with humans globally warrants in-depth analysis of microbial compositions by ethnicity, region, diet, and industrialization status to maximize the benefit of microbiota-based interventions to one and all. Microbial analyses were performed to evaluate the risk of disease in relation to microbiome dysbiosis and abrupt changes following immigration could inform policy-makers and decision-making and aid in developing personalized therapeutics to improve the standard of care for all individuals across the globe.