Frequent exposure to microbes in the environment has been associated with better immune system functioning. In addition, living in green areas and engaging in activities outdoors in nature have been linked with improved breathing and health-promoting changes in the gut. But whether indoor gardening favors having a more diverse population of healthy microbes and supports the immune system remains to be explored. Check out this study doing just that with participants from two cities in Finland.
Key Takeaways
Indoor gardening leads to a more diverse population of microbes in the skin and to higher levels of a molecule that promotes healthy immune reactions
Benefits in the skin population of healthy microbes and in immune functioning are only seen when using a growing medium rich in microbes
Microbes from plants, animals, and natural waters can colonize parts of the human body such as the skin and gut where they profoundly affect our health. According to the “biodiversity hypothesis,” having contact with natural environments enhances the human microbiota — the collection of all microbes living in association with the human body — and supports a healthy immune system. In fact, studies have shown that exposure to microbes in soil helps with the development and functioning of the immune system.
Studies have shown that exposure to microbes in soil helps with the development and functioning of the immune system.
With immune functioning issues becoming more prevalent in developed countries, concerns have been raised regarding the loss of immune defenses derived from nature as a result of a global shift of populations from rural to urban areas. Research in Finland and elsewhere in Europe has indeed indicated that a greener environment around the home, including more species of plants and more diverse bacteria in the skin, supports health. Such a benefit has been shown as early as the first year of life. Urban spaces seem in fact to lack elements that are key to developing and maintaining proper immune regulation.
Indoor Gardening Increases Diversity of Skin Microbes
Trials in people living in urban areas have explored the impact of vegetation and soil rich in microbes on immune regulation and on the human microbiota — which besides bacteria, includes fungi, viruses, and other microorganisms. Their results have generally shown better immune regulation and a more diverse microbial population in the human body. However, they were mostly small.
Gardening, in particular, has been shown to provide a number of health benefits, supporting cognition and mental well-being. While a few studies showed that indoor green walls and having contact with soil rich in microbes promote better immune functioning and a healthier microbial population in the skin, no evaluations had been made of indoor gardening as a way to provide these two types of benefits at the same time.
Studies have shown that indoor green walls and having contact with soil rich in microbes promote better immune functioning and a healthier microbial population in the skin.
Investigators in Finland addressed this knowledge gap by recruiting healthy adults from two cities and providing them with growing medium and crop species for indoor gardening. Fifteen participants were given a growing medium rich in microbes, whereas 13 were assigned a poorer, peat-based growing medium. Such a clinical trial addressing the links between indoor gardening, microbes living in the human body, and immune functioning was the first of its kind, the scientists noted.
Crop species used by both groups included lettuce, white mustard, radish, garlic, ginger, pea, and fava bean, a set chosen as some of these species can be harvested shortly after sowing, and some others later on. According to the investigators, the fact that the participants were exposed to the environmental microbes not only through their skin but also via the digestive tract by consuming the crops marked a difference to previous studies. Potential effects on the microbial population of the gut, where trillions of microbes normally live, might result in changes in immune functioning, the team noted.
The rich microbial mixture contained materials including tree bark and mulch, dung, leaf litter, and agricultural sludge. Besides other instructions, all participants were told to work barehanded, monitor moisture by inserting a finger deep into the growing medium, water, and mist with the spray bottle, harvest, and resow. The trial was conducted in winter, which likely minimized contact with soil unrelated to the experiments.
Results first showed that exposure to the growing medium rich in microbes led to higher blood levels of a molecule called interleukin-10 one month later. Interleukin-10 has been associated with benefits for several immune regulation issues.
Also, the same participants showed increased diversity of several groups of bacteria in skin samples taken from the back of the hand. Again, no such differences were seen in participants gardening with the poorer growing medium.
In addition, the findings further revealed that although the complexity of the skin’s bacterial networks grew in both groups, they were multiple times higher in participants exposed to the richer growing medium. After one month, the skin bacterial population in the group using the richer medium had more microbial diversity and more intricate connections between microbes than controls.
Among specific groups of bacteria whose diversity increased through gardening were Bacteroidetes, known to promote digestive system health, and Cyanobacteria, which help protect the skin against UV-induced damage.*
Overall, the trial’s results support the authors’ hypothesis as daily gardening with microbially rich growing medium enriched the skin population of microbes and drove changes in immune functioning a month later. They also show the benefits of handling and being exposed to microbes year-round, as the experiments were conducted during the winter season.
The study showed that one month of indoor gardening increased the diverse population of microbes in the skin and resulted in higher levels of a molecule that optimizes immune reactions.
While more studies are needed to assess whether these changes persist over longer periods and also happen in people from other regions, the findings demonstrate how indoor gardening in cities is a cost-efficient way to increase your exposure to beneficial microbes. That can be a valuable activity to implement in various contexts and stages of life, from kindergartens and schools to offices and nursing homes.*
Support a Healthy Gut Microbiome with Qualia Synbiotic
Qualia Synbiotic is a combination of prebiotics, probiotics, postbiotics, fermented foods, herbs, and digestive enzymes that work complementarily to support digestive health, gastrointestinal performance, the gut microbiota, the gut-immune axis, and the gut-brain axis. We developed Qualia Synbiotic to support gut health, gastrointestinal performance, and the gut-brain axis.*
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Referenced study:
Saarenpää, M, Roslund, MI, Nurminen, N, Puhakka, R, Kummola, L, Laitinen, OH, Hyöty, H, Sinkkonen, A: Urban indoor gardening enhances immune regulation and diversifies skin microbiota — A placebo-controlled double-blinded intervention study. Environ Int. 2024, 187:108705. doi: 10.1016/j.envint.2024.108705
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