How urbanization affects microbiota in Senegal
Access to running water, healthcare, and a varied diet does not prevent some babies from having a less mature gut microbiota than others born in an underprivileged rural environment. This is the main finding of a study 1 carried out in Senegal.
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About this article
The environment – diet, hygiene, place of residence, lifestyle, pollutants, drugs, etc. – shapes the evolution and composition of the gut microbiota. But so do genetics.
Changes in the microbiota are associated with certain diseases, such as obesity and allergies. Since lifestyle contributes to microbiota changes that influence disease, a team of researchers set out to determine the impact of urbanization on the gut microbiota, while overcoming genetic factors.
Senegalese Fulani people as a study model
They recruited 60 young Senegalese Fulani women and their newborn infants, most of whom were delivered vaginally. All the women belonged to the same ethnic group and were, therefore, genetically unified. However, they lived in radically different environments:
- Half lived in a “traditional” (rural) environment with little or no access to amenities (electricity, health centers, running water, etc.) and a diet that was not very diversified;
- The other half lived in Dakar (urban), with electricity, running water, healthcare, and a much more diversified diet.
The “urban” mothers had a higher body mass index (sidenote: Body Mass Index (BMI) Body Mass Index (BMI) assesses the corpulence of an individual by estimating the body fat mass calculated by a ratio between weight ((kg) and height squared (m2). https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm https://www.euro.who.int/en/health-topics/disease-prevention/nutrition/a-healthy-lifestyle/body-mass-index-bmi ) than the “rural” mothers.
The scientists took stool samples from the mothers and babies at two points in time: within six months of delivery (T1), then one year later (T2).
5 major factors that influence the gut microbiota of babies 2
• Mode of delivery: a child born by vaginal delivery has greater microbiota diversity than a child born by cesarean;
• Gestational age at birth: premature delivery has an adverse impact on microbiota colonization;
• Breastfeeding: breast milk provides beneficial microbes, nutrients, immunoglobulins, and antibacterial agents, all of which are absent from infant formula;
• Environment: siblings, eating habits, place of residence, etc. may modulate microbiota colonization;
• Genetics: a study of children under the age of ten showed that microbial similarity between identical twins was higher than between fraternal twins or unrelated children. 3
Better living conditions, but adverse effects on gut microbiota
The researchers observed a “delayed maturation” of the gut microbiota in urban infants, characterized by lower microbial diversity. This deficit was not observed in rural infants. This may indicate that urban sanitary conditions, pollution, or diet influence the evolution of their microbiota.
On the other hand, differences in microbiota composition between urban and rural babies were less significant than those between urban and rural women. According to the authors of the study, this may be due to the fact that the babies had been exposed to certain urbanization factors, such as diet, for a shorter time than their mothers, with dietary diversification generally not occurring until the sixth month.
However, according to the authors, these differences may also be explained by the exposure of urban mothers to a greater number of factors – urbanization, as well as a higher prevalence of parasitism and excess weight – than rural mothers.
Nature and microbiota: how does it affect your health?
Significant health consequences
The researchers also noted that infants with an immature microbiota at one year of age were more susceptible to respiratory and dermatological infections at T2 than rural infants, but not at T1. They also had more allergy symptoms. Lastly, the urban mothers had a higher body mass index (sidenote: Body Mass Index (BMI) Body Mass Index (BMI) assesses the corpulence of an individual by estimating the body fat mass calculated by a ratio between weight ((kg) and height squared (m2). https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm https://www.euro.who.int/en/health-topics/disease-prevention/nutrition/a-healthy-lifestyle/body-mass-index-bmi ) than the rural mothers, as well as a higher presence of Lachnospiraceae and Enterobacter, bacteria that have been associated with obesity in numerous studies.
According to the authors, although the study suggests that urbanization alters the microbiota, it does not clearly identify the factors involved among all those to which mothers and their children are exposed (water sanitation, diet, pollution, working conditions, etc.). Further studies are therefore required before any conclusions can be drawn.
