Many studies have been carried out to try to figure out the factors that influence the diversity of bacteria inhabiting our intestines and the impact these have in the developement of various diseases such as diabetes, obesity1, Inflamatory Bowel Disease2, neurological ailments3, amongst others. For this, the relative abundance and diversity of bacteria is analyzed in healthy individuals and is compared with such of individials that present a series of clinically relevant ailments. Thus trying to elucidate the characteristic bacterial composition of each group and being able to propose therapies in the future that lead individuals to have a healthier microbiota.
Nonetheless, this is no easy task since multiple factors influence the bacterial composition of the intestines. These factors include: age, body bass index, diet, lifestyle, immune system, antibiotic use and genetics. In order to analyze multiple factors, one investigation gathered the information posed in previous studies and analyzed the influence of geography, ancestry and lifestyle, in the intestinal microbial diversity of healthy individuals of various geographic regions.
In order to analyze multiple factors, one investigation gathered the information posed in previous studies and analyzed the influence of geography, ancestry and lifestyle, in the intestinal microbial diversity of healthy individuals of various geographic regions.
The study concluded that lifestyle is the most impactful factor in the characteristic intestinal bacterial diversity of each population. These lifestyles can be resumed in 3 large groups based in their means of livelihood: hunting-harvesting, agriculture-fishing and occidental industrialized urban life.
The hunting-gathering is characterized by the consumption of tubers, fruits, plants, seeds and the meat of wild game. On the other hand, populations of farmers are characterized by the consumption of fruits, vegetables, plants and the meat of domesticated animals. Lastly the industrialized urban societies show a high consumption of protein rich processed foods and a high quantity of fatty acids.
An interesting discovery made was that there´s a distinctive reduction in the microbial diversity parting from a hunting-gathering lifestyle to the industrialized urban lifestyle.
An interesting discovery made was that there´s a distinctive reduction in the microbial diversity parting from a hunting-gathering lifestyle to the industrialized urban lifestyle. The large diversity of microbial species present in the hunting-gathering group, is suggested to possibly benefiting their capacity to digest different types of foods depending on seasonality, and likewise the presence of beneficial bacteria could counteract the presence of pathogens. While the inhabitants of cities could have greater access to medical services and the use of antibiotics, that influence in the quantity and variety of bacteria in the intestine.
Depending on the lifestyle, the bacterial genres with larger and smaller representation in the intestinal microbiota were: Prevotella with the greatest abundance in hunters-gatherers; this bacterial genre is associated with a larger ability to digest fiber rich foods, and a low abundance of Bacteroids that are associated with protein and animal fat rich diets. On the other hand, in inhabitants of industrialized cities, a larger quantity of Bacteroids and an almost null one of Prevotella were found. Whilst the farmer group showed an intermediate abundance between these groups, thus demonstrating a transition from the hunting-gathering lifestyle -> farmer -> urban life.
It’s worth emphasizing that in the hunting-gathering and farmer groups the presence of the Treponema genre has been noticed, genre lacking on individuals of the urban industrialized societies5. The presence of the Treponema genre has also been reported in the intestinal microbiome of ancient humans6 and in another primate species4. This bacterial genre could contribute in the metabolization of polysaccharides such as xylan, present in vegetables5.
In a similar fashion, other study7 that confirms the influence of lifestyle, analyzed the intestinal microbiota of individuals who changed their lifestyle from farming to a characteristic industrialized city one, by migrating to the USA. 6 months after migrating, the individual´s microbiota changed drastically, with a pronounced loss of microbial diversity and a noticeable increase of up to ten times the proportion of Bacteroids in relation to Prevotella. Another interesting aspect was that, by analyzing these individual´s diet, it was discovered that the latter was not fully responsible for the identified changes in micriobiota, it is consequently proposed that there are other factors that may be contributing to these changes, such as the consumption of municipal water, antibiotics and antiparasites and even stress and physical activity.
Without a doubt there´s still many things to be studied in the field of human intestinal microbiota. Nonetheless, these results clearly reflect the changes that populations have been exposed to throughout the years, since the beginning of farming and the domestication of animals, to the transition to a lifestyle with high consumption of processed foods, which has led to a loss of microorganisms, that played in some moment of our history a metabolic role important to the utilization of nutrients stemming from different food sources.
Thereupon, it is clear that all the elements that form our dietary lifestyle, are factors that determine the type of bacteria that inhabits our intestines, which in turn, conditions the metabolic becoming of human populations, something that should also be considered when using therapies that alter the intestinal microbiotal composition.
- Barlow, G. M., Yu, A. & Mathur, R. Role of the Gut Microbiome in Obesity and Diabetes Mellitus. Nutr. Clin. Pract. 30, 787–797 (2015).
- Ni, J., Wu, G. D., Albenberg, L. & Tomov, V. T. Gut microbiota and IBD: causation or correlation? Nat. Rev. Gastroenterol. Hepatol. 14, 573–584 (2017).
- Tremlett, H., Bauer, K. C., Appel-Cresswell, S., Finlay, B. B. & Waubant, E. The gut microbiome in human neurological disease: A review: Gut Microbiome. Ann. Neurol. 81, 369–382 (2017).
- Gupta, V. K., Paul, S. & Dutta, C. Geography, Ethnicity or Subsistence-Specific Variations in Human Microbiome Composition and Diversity. Front. Microbiol. 8, 1162 (2017).
- Angelakis, E. et al. Treponema species enrich the gut microbiota of traditional rural populations but are absent from urban individuals. New Microbes New Infect. 27, 14–21 (2019).
- Tito, R. Y. et al. Insights from Characterizing Extinct Human Gut Microbiomes. PLoS ONE 7, e51146 (2012).
- Vangay, P. et al. US Immigration Westernizes the Human Gut Microbiome. Cell 175, 962-972.e10 (2018).
Is a Biologist from the National Polytechnic Institute (IPN), Master of Science from CINVESTAV/ Irapuato, also from IPN, where she worked in the area of Synthetic Biology. She is currently working on her doctoral thesis at the LIIGH of UNAM, in the group of Dr. María C. Ávila Arcos.
