Are urban green spaces good for our microbiota?
Diet, pollution, urbanization... many factors influence the composition of our various microbiota and are potentially linked to the increased prevalence of non-communicable diseases. In response, exposure to green spaces allows new microorganisms to colonize our microbiota, potentially to their benefit.
The microbial world present in the air, soil and plants is considered critical for our health. Certain theories suggest that low exposure to green spaces and to the microorganisms found in them has contributed to the contemporary rise in obesity, diabetes mellitus, and allergies. Therefore, a better understanding of the interactions between man and nature, and especially between microbiota and environment, seems key to fighting these non-communicable diseases. To this end, a team of scientists evaluated the impact of green spaces on the composition and diversity of the skin and nasal flora of three individuals following visits to urban green spaces in three different countries, Australia, India, and the UK.
Green spaces increase microbial diversity
During their walks, the participants took soil, leaf, and air samples in order to analyze the bacteria in the environment. They also took samples from their nose and skin before and after each exposure to the environment so as to assess the impact of green spaces on their microbiota. The analysis revealed that the skin flora had changed following the walk: it was richer in bacteria, more diverse and closer to that of the soil, evidence that environmental bacteria had colonized the skin. Furthermore, the composition of the nasal microbiota was similar to that of air samples.
Even more interesting was the overall similarity between the changes in microbial diversity and composition in the three countries visited, even though many factors known to influence the composition of the microbiota, such as pollution, humidity, or diet, differed between these three countries. It is not yet known how long these changes in the flora last, but previous studies suggest that most environmental bacteria transferred to humans disappear after 2 hours, with less common types potentially persisting for up to 24 hours on the skin. Further research is required to establish whether there are any health benefits from these microbial changes, but in the meantime, feel free to roll around in the grass!
Selway CA, Mills JG, Weinstein P, et al. Transfer of environmental microbes to the skin and respiratory tract of humans after urban green space exposure. Environ Int. 2020 Sep 22;145:106084. doi: 10.1016/j.envint.2020.106084.