On Nutrition
Back in February, I wrote the column “Do you really want to live forever, or just be healthier for longer?“ In it, I mentioned that being in green spaces can contribute to a robust gut microbiome. I received a few emails from readers asking me, “How?” As an avid gardener and camper — and general lover of green spaces — I am delighted to answer that question in this week’s column.
A healthy gut microbiome — the community of trillions of bacteria and other microorganisms that reside in our intestines, plus their genes — is important for overall health. But the environment has a microbiome, too, and while research in this area is still limited, it lends support to the idea that the gut and environmental microbiomes are linked, and that human contact with soil microbial communities plays an important role in human health.
Just as the human gut is not sterile, soil is not sterile. It’s home to billions of bacteria, fungi and other microbes, especially in the top foot. A growing body of research is finding that the soil microbiome may influence the human gut microbiome both directly and indirectly. Indirectly, plant roots are immersed in soil, and soils rich in biodiversity not only produce more nutritious plant foods, they can crowd out “bad” microorganisms that could affect plant health and our health.
Directly, we’re in contact with soil from early childhood as our gut microbiotas were developing. We sit on the lawn, garden, camp, hike and swim in natural bodies of water. We inhale soil and drink water that has passed through soil at one point. We pet dogs that rolled around outside. We eat fresh, raw produce. Some researchers have wondered if the health effects of eating adequate fruits and vegetables — or not — could be partially due to the microbes we do or don’t ingest.
Because our gut and gut microbiota play a big role in the health of our immune system, it’s likely that exposure to soilborne microorganisms also plays an important role. A 2020 study found that gut microbial diversity — and healthy stimulation of the immune system — increased among children at select day care centers that covered part of the play yard gravel with forest floor and sod, added planters for growing annual plants, and provided peat blocks for climbing and digging. Another 2020 study found that proximity to a natural environment plus pet ownership has the capacity to alter gut microbial diversity in formula-fed infants to more closely resemble that of breastfed infants.
Here are a few ideas for nurturing our gut microbiomes by exposing ourselves into nature, even if we don’t get dirty:
- Strengthen connections to nature in everyday life. Visit parks, walk barefoot or sit on a picnic blanket in grassy areas where herbicides aren’t a concern. Walk on nature trails and swim in lakes and rivers. If you like to hike or camp in the woods, good news: forest soil is two-to-five times richer in microbes than even soil on an organic farm.
- Plant a garden. Digging in the soil, pulling weeds, planting seeds and harvesting root vegetables puts you into direct contact with the soil.
- Eat more fresh fruits and vegetables. While washing produce is important from a food safety standpoint, some gut microbiome researchers suggest being less thorough when the produce comes from your own garden.
- Wash hands less. It’s important to wash hands that may have been exposed to toxins, pesticides or viruses, but maybe be less vigilant after gardening or petting a dog.