A growing body of research is demonstrating just how closely the microorganisms in soil, plants and humans are interconnected – a topic covered in a previous article (see ‘One Health’: How the microbiomes of soil, plants and the human gut are interconnected, Part I). This article now describes specific interactions. For example, contact with nature from an early age can have a positive influence on microbial diversity in the gut. Growing up in a rural environment, as well as playing in nature-based day-care centres, is beneficial in this regard. A study from 2025 also demonstrates such an effect in adults, where even brief stays in green spaces had a positive impact on the gut microbiota. The method of food production also plays a role. This is confirmed by a study comparing the microbiome of biodynamically grown apples with that of conventionally grown fruit. The way in which microorganisms interact with one another is highly complex, but one thing is becoming increasingly clear: health is a collaborative process in which everyone is involved – ‘One Health’.
The microbiomes of soil, plants and the human gut are interconnected and interact in highly complex ways – as demonstrated by a review article by Ma et al. (2025), (see ‘One Health’: How the microbiomes of soil, plants and the human gut are interconnected, Part I ) [1]. It becomes clear that it is not only food that influences the gut microbiota, but also the environment in which one lives. The ‘farm effect’ is already well known: children who grow up on a farm tend to develop allergies less frequently than children from urban areas [2]. A Finnish study also shows that the kindergarten environment has an influence: children who spend more time playing on forest floors and lawns have a more diverse microbiota compared to children from urban kindergartens with no contact with nature. This increased diversity is associated with a higher prevalence of bacteria that support the immune system and can thus help prevent allergies [3]. Whether this link also applies to adults has so far been investigated much less frequently. Against this background, researchers conducted a randomised study in China to analyse how spending time in urban green spaces affects the microbiome of adults [4].
A total of 30 healthy adult participants took part in the study and were divided into three groups: the first group spent time in outdoor green space (GS), the second group in outdoor non-green space (NGS), and the third group spent their time indoors (indoor group). The participants were instructed to spend two hours a day in their respective assigned environments for seven consecutive days. The park used by the GS group featured a wide variety of plant species, including trees, shrubs and grasses. The participants in the NGS group spent their time in an open outdoor area near shopping streets. The indoor group spent the two hours in a university lecture theatre. Before and after the intervention, the researchers collected stool and saliva samples to analyse the microbiota. All participants were advised to maintain a balanced diet.
At the start of the study, the average diversity of the gut microbiota was comparable across all three groups. Following the intervention, the GreenSpace group showed a significantly increased microbial diversity (p < 0.05). Furthermore, an increase in health-promoting bacteria, such as Lactobacillus, was detected in the stool samples. In the NonGreenSpace group, however, which spent time in an urban environment, a decline in microbial diversity was observed. Analysis of the stool samples from the Indoor group revealed hardly any changes. The gut microbiota can evidently change rapidly and in a detectable manner.
Spending time in a park is often associated with reduced stress. Lower stress levels can influence gut function and thereby bring about changes in the composition of the gut microbiota. Furthermore, by breathing in air or coming into contact with surfaces in natural environments, people are exposed to microorganisms. These can interact with the microorganisms already present in the gut, thereby triggering various biological responses. The effects of these interactions depend on the bacterial species involved. A recent study from 2026 showed that certain bacteria can introduce proteins into human cells that influence key signalling pathways of the immune system. The researchers see a possible link here with autoimmune diseases such as Crohn’s disease [5]. Changes in the gut microbiome are also associated with conditions such as obesity and type 2 diabetes, as well as with stress and mental health disorders. Indicators of a disrupted gut microbiome include low microbial diversity, high levels of pathogenic bacteria and insufficient levels of beneficial bacteria such as lactobacilli [6].
However, over the course of a person’s lifetime, diet has so far been regarded as one of the strongest influences on gut bacteria. A high-fibre, plant-based diet comprising whole grains, pulses, vegetables, fruit and nuts is beneficial to health because this type of diet increases microbial diversity [6 ].
Where antibiotics are used in animal husbandry – as is widespread in conventional agriculture – antibiotic resistance genes can be detected in the environment. These are pathogenic insofar as antibiotic resistance can be transmitted to humans. This is demonstrated by the study described in Part I, which investigated pig farms and their surroundings [7].
When it comes to plants and plant-based products, the method of cultivation plays a major role. One study compared the microbiome of apples from conventional and biodynamic cultivation [8]. Whilst the total number of bacteria on the apples differed only slightly, their composition did: biodynamically grown apples exhibited significantly higher microbial diversity and a more even distribution of bacterial communities than conventionally grown apples. Furthermore, the researchers found fewer potentially pathogenic microorganisms on the biodynamically grown apples.
All these findings underscore the close connection between soil, plants and humans: microorganisms interact with one another and across species boundaries. And they do so even within a short period of time. A diverse soil microbiome, such as that found in biodynamic soils, promotes microbial diversity in plants, which in turn can influence the human gut microbiome via the food we eat. Health begins in the soil in which plants and our food grow. It extends beyond our plates to the tiniest cells in the gut. It is a form of health that we all share: ‘One Health’.
References
[1] Ma H, Cornadó D & Raaijmakers JM (2025): ‘The soil-plant-human gut microbiome axis into perspective’. Nature Communications 16, 7748.
https://doi.org/10.1038/s41467-02562989z
[2] Illi S, von Mutius E, Neuherberg (2018): ‘Die PASTURE-Geburtskohorte’ in: Pädiatrische Allergologie 4. Gesellschaft für Pädiatrische Allergologie und Umweltmedizin (GPA). Available at: https://www.gpau.de/fileadmin/user_upload/GPA/dateien_indiziert/Zeitschriften/Paed_Allergologie_2018_4.pdf, accessed on 9 June 2026
[3] Roslund MI, Puhakka R, Grönroos M, Nurminen N, Oikarinen S, Gazali AM, Cinek O, Kramná L, Siter N, Vari HK, Soininen L, Parajuli A, Rajaniemi J, Kinnunen T, Laitinen OH, Hyöty H, Sinkkonen A, ADELE research group (2020): ‘Biodiversity intervention enhances immune regulation and health-associated commensal microbiota among daycare children’ Science Advances 6:eaba2578.
https://www.science.org/doi/10.1126/sciadv.aba2578
[4] Wang L, Li JY, Zhu XQ, Jiang JC, Li C, Zheng ZH, et al. (2025): ‘Intervention effects of exposure to green spaces on the human microbiota: A randomised controlled trial in young Chinese adults’. Ecotoxicology and Environmental Safety 296:118183. https://doi.org/10.1016/j.ecoenv.2025.118183
[5] Young V, Dohai B, Halder H. et al (2026): ‘Effector-host interactome map links type III secretion systems in healthy gut microbiomes to immune modulation’ Nature Microbiology 11:442–60.
https://doi.org/10.1038/s41564-025-02241-y
[6] Backes G (2026): ‘Das Mikrobiom – Update für die Ernährungsberatung’ in: DGE-Blog. Deutsche Gesellschaft für Ernährung e. V. (DGE). Available at: https://www.dge.de/blog/2026/das-mikrobiom-update-fuer-die-ernaehrungsberatung/ accessed on 16 June 2026.
[7] Song L, Wang C, Jiang G, Ma J, Li Y, Chen H & Guo J (2021): ‘Bioaerosol is an important transmission route of antibiotic resistance genes in pig farms’. Environment International 154, 106559.
https://doi.org/10.1016/j.envint.2021.106559
[8 ] Wassermann B, Müller H, Berg G (2019): ‘An apple a day: Which bacteria do we eat with
organic and conventional apples?” Frontiers in Microbiology 10:1629. https://doi.org/10.3389/fmicb.2019.01629
Further articles on the topic of microbiota:
Playing outdoors helps prevent allergies in children
https://www.sektion-landwirtschaft.org/ernaehrung/artikel/ea/draussen-zu-spielen-beugt-allergien-bei-kindern-vor
Bacteria from the field to the gut – a comparison of biodynamic and conventional apples
https://www.sektion-landwirtschaft.org/ernaehrung/artikel/ea/bakterien-vom-acker-bis-zum-darm-ein-vergleich-von-biodynamischen-und-konventionellen-aepfeln
Off to the countryside – a healthy immune system thanks to the ‘farm effect’
https://www.sektion-landwirtschaft.org/ernaehrung/artikel/ea/raus-aufs-land-gesundes-immunsystem-dank-bauernhofeffekt
Fermented foods for sharp minds
https://www.sektion-landwirtschaft.org/ernaehrung/artikel/ea/fermentierte-lebensmittel-fuer-kluge-koepfe
Glyphosate and the microbiome
https://www.sektion-landwirtschaft.org/ernaehrung/artikel/ea/glyphosat-und-das-mikrobiom
Microbiota
https://www.sektion-landwirtschaft.org/ernaehrung/artikel/ea/microbiota
