By Dietitian Laura Tilt.
Most of us have the instinctive sense that spending time outdoors can have a positive effect on our state of mind. But evidence suggests the benefits of natural environments reach beyond the brain, right down into the gut.
It’s Great, Outdoors
If there’s one thing that Mother Nature is guaranteed to deliver on, it’s a sense of wellbeing. Whether you’re lying under a tree in the park, watching a sunset, hiking up a hill or walking along a beach, being in the great outdoors offers restorative qualities that benefit mind and body.
Happily, the apparent benefits of nature for health are backed by research. Studies investigating the effects of nature on mental and emotional health show that being in a natural environment can improve mood, lower stress and help us feel more relaxed. Listening to nature sounds like ocean waves or birdsong can switch our nervous system into ‘rest and digest’ mode, whilst exercising in a green space (such as a park) appears to be more beneficial for mental health than exercising indoors.
And because nature doesn’t require our direct attention, it can actually help us recover from mentally fatiguing tasks, making an after work walk the kind of tonic that we can easily benefit from. Some studies even show that the mental wellbeing of populations is linked (at least partially) with their proximity to green and blue environments like parks and oceans.
So what’s this all got to do with gut health?
Well firstly, we know that there is a strong relationship between mental health and gut health. Stress can impact gut function and the microbiome in unwanted ways, so anything which helps to manage stress will arguably have a positive impact on your gut health too.
But the benefits don’t stop at the level of the mind. In fact, the benefits of nature seem to travel right down to the microbes in your gut.
Nature and Your Gut
Scientists have suspected for some time that the natural environment may influence the human gut microbiome. Research has shown that populations living in urban environments (like towns and cities) have less diverse microbiomes than those living in rural environments and farms. At the top of the tree in terms of microbiome diversity are populations who still follow a traditional hunter-gatherer lifestyle, such as the Hadza tribe in northern Tanzania. Microbiome diversity matters because it seems to be a marker of microbial fitness - the more diverse the microbes in your gut, the more robust they seem to be to disturbances from antibiotics for example. A lack of diversity on the other hand, has been associated with a number of different conditions. This isn’t necessarily a case of cause and effect, but it is an interesting observation.
Diet and other lifestyle factors aside, what causes these differences? One explanation is that urban living (in towns and cities) means reduced contact with nature and reduced exposure to beneficial environmental microbes, which may play an important role in training our immune systems. Whilst our ancestors evolved in close contact with nature and the soil (which served as a medium for growing and foraging food and providing shelter), the majority of the world’s population now live in cities, leading to a loss of contact with the natural environment. At the same time, we’ve become less involved with food growing, which means less exposure to nature and importantly, soil.
Just like your gut, the soil beneath your feet is heavily populated with microbes. And, just like the microbes in your gut, the microbes in the soil protect against pathogens and support the immunity of the plants growing in it. But the change to mechanical means of farming together with the use of fertilisers and pesticides means soil biodiversity has been reduced, which probably means less exposure to microbes which may benefit our health.
Altogether, these changes have led some researchers to hypothesise that our modern lifestyle and loss of contact with natural environments and soil is adversely affecting the human gut microbiome.
In 2018, a group of Finnish researchers explored how another outdoor activity - gardening - may impact the microbiome of a small group of healthy city dwelling adults. Over a period of two weeks, one half of the group was asked to rub their hands with a mix of soil and plant material three times a day before washing with water, whilst the other group acted as controls. Stool samples and skin swabs taken at day 0, 14 and 35 revealed that compared to the control group, the adults whose hands had been exposed to the soil had increased diversity in their stool microbiome after the intervention period.
More recently, the same research group showed that Finnish adults living in homes with access to gardens containing shrubs and flowering plants had more beneficial microbes in their gut than those living in built up city areas with no access to a garden.
There’s no doubt that more research is needed before we can make any conclusive statements about the impact of the natural environment on the gut microbiome, but for now, there seems good reason to embrace the great outdoors, particularly if you are a city dweller.
Bringing Nature Into Your Life
If reading this has made you reflect on your proximity to nature and you’re wondering how to bring more nature into your life, here’s some inspiration.
Take your activity outdoors
Commit to taking a daily walk in a green space, or move your usual movement (be that running, cycling or yoga) outdoors when the weather allows. For support and motivation, try the couch to 5k app, or follow the Swedish trend for plogging - jogging whilst picking up litter. And if you have a garden, patio or terrace, make the most of the space by eating breakfast outside.
Explore your area
Find out where your local nature reserve is here, seek out your local beach for a weekend walk or plan a camping trip. Or for an experience closer to home, stay up late and star gaze in the garden on a clear night.
Grow your own
If you’re new to gardening, take heart - even the most novice gardener can grow lettuces and herbs in a window box. If you have a balcony or a patio you can buy deeper pots and grow French beans, radishes, tomatoes and spring onions.
Bring the outdoors into your home
Nature can have a calming effect, so bringing the outdoors in can help create a relaxing environment. If you can, arrange a spot to sit next to the window with cushions, grow flowers on a windowsill or cultivate a few pot plants on your desk to create connection with nature.
Gould Van Praag, C. D., Garfinkel, S. N., Sparasci, O., Mees, A., Philippides, A. O., Ware, M., Ottaviani, C., & Critchley, H. D. (2017). Mind-wandering and alterations to default mode network connectivity when listening to naturalistic versus artificial sounds. Scientific Reports. https://doi.org/10.1038/srep45273
Yard vegetation is associated with gut microbiota composition | Elsevier Enhanced Reader
Microorganisms | Free Full-Text | Does Soil Contribute to the Human Gut Microbiome?
Nurminen, N., Lin, J., Grönroos, M., Puhakka, R., Kramna, L., Vari, H. K., Viskari, H., Oikarinen, S., Roslund, M., Parajuli, A., Tyni, I., Cinek, O., Laitinen, O., Hyöty, H., & Sinkkonen, A. (2018). Nature-derived microbiota exposure as a novel immunomodulatory approach. Future Microbiology, 13(7), 737–744. https://doi.org/10.2217/fmb-2017-0286