Spending time outside has long been associated with feeling better…but why? Does fresh air really do us good, or is there a more at play in our interaction with the natural world? At GJLD, we spend many hours a week in the landscape, and anecdotally, we can confirm the restorative qualities. But we also wanted the cold hard facts – is being in nature a placebo effect, related to being away from the daily grind, or are there quantifiable health outcomes from being outside? We did a deep dive into the research and found that there are significant health benefits associated with being in the landscape, largely due to the soil microorganisms beneath our feet, and the trees towering above us. We summarize the research below.
Soil Microorganisms and Human Health
Scientists studying our own gut microbiome discovered just how similar our gut bacteria are to soil bacteria. The theory is that they evolved alongside each other, over thousands of years, through the food that our ancestors ate. Our gut microbiome is known to influence our mood, immune system, and central nervous system. In fact, it’s colloquially called our second brain. As society becomes more urbanized, surrounded by manmade materials, and consuming a processed food diet, our gut microbiome has become increasingly less diverse. As land management turns toward industrial farming and synthetically maintained landscapes, soil microbe diversity is also decreasing.
Fortunately, restoring your gut microbiome is relatively simple: eat a high fiber diet (plants) and spend time in an organic landscape. Beneficial soil microbes, such as Microbacterium Vaccae, become airborne and are inhaled as we walk through the landscape. Gardening, eating off the vine, and playing in the dirt are other great ways to reconnect with these microorganisms, our so-called “Old Friends.”
Health Benefits of Soil Bacteria M. Vaccae
There have been many fascinating studies on M. Vaccae in just the last decade. Some findings on the link to human health include:
- Increased serotonin levels and brain neuron growth – displayed in mice fed M. Vaccae. They completed mazes twice as fast and exhibited neuron growth in their brains. These mice also had increased levels of tph2, an enzyme involved in the biosynthesis of serotonin.
- Reduced stress and anxiety – mice in the study were 50% less likely to exhibit stress-induced symptoms like colitis (cellular damage to the colon). When exposed to a larger, aggressive mouse, they exhibited less anxiety symptoms and more proactive behavior. Scientists believe M. Vaccae could be used as a PTSD treatment in humans.
- Reduced inflammation, improved immune response – M. Vaccae’s anti-inflammatory character affects our neuroinflammatory processes. When fed to rats, it enables their central nervous system to regulate more effectively and “mitigates the neuroinflammatory and behavioral effects of stress.”
Furthermore, children growing up in rural, agricultural environments were studied against city kids. The rural children (studied as adults) had better immune response during stress, and exhibited fewer allergies and lower cases of asthma. Researchers posit that exposure to soil microbes, especially as children, helps “educate” our immune system and shape our immune response as adults.
Trees, Forest Bathing & Human Health
Another body of research connecting nature to human health originated in Japan. Shinrin-yoku, which translates to Forest Bathing, became part of the Japanese national health program in 1982 to address a spike in mental health troubles, stress and suicide rates during the technical revolution of the 1980s.
Forest bathing combines meditative practices within a forest setting. To practice shinrin-yoku, carve out some time to sit or walk slowly through the woods, paying close attention to your breathing and five senses; allow yourself to notice all the sights, smells, sounds, and touch of the natural world around you.
Since the 80s, forest bathing has been studied extensively in Japan and around the world and linked to a wealth of health benefits.
Stress, Anxiety & Depression Reduction from Forest Bathing
Forest Bathing has been shown to reduce stress and relax the body. On a physiological level, after a forest bathing session, study participants exhibited lower rates of salivary cortisol, lower pulse rates, lower blood pressure, lower sympathetic nervous activity and higher parasympathetic nervous activity than those in the control group.
Participants were also asked to rate their mood using the Profile of Mood States (POMs) before and after Forest Bathing. All participants showed an improvement in mood afterwards, but the change was especially notable in those participants with depressive tendencies: their POMs scores increased dramatically, and in some instances, their scores no longer differed from the participants without depressive tendencies. Stress inhibits immune system function, so reducing stress has the added benefit of improve immune response.
Phytoncides Effect on Our Immune System
Many of the health benefits associated with trees can be traced to phytoncides, compounds that trees and other plants produce to help ward off predators and invaders. The anti-bacterial and anti-fungal properties of phytoncides are transferred to humans when we spend time in the forest and breathe in phytoncides as volatile organic compounds (VOCs).
Multiple studies have recorded a correlated increase in a type of white blood cell our bodies produce – natural killer cells or NK cells – when inhaling phytoncides. NK cells are known to fight infection and cancerous cells and are a valuable component of our immune defense.
Improved Sleep Linked to Phytoncides
Two common phytoncides in trees are α-pinene and 3-carene. They “enhance inhibitory synaptic responses” which positively promote sleep in the same way that common sleep-aid pharmaceuticals work (they “modulate the GABAA BZD receptor”). One study found exposure to α-pinene and 3-carene “enhance[s] the quantity of [non-rapid eye movement sleep] without affecting the sleep quality.”
Inflammation, Lung, and Heart Health Benefits
Phytoncides α-pinene and β-pinene have been demonstrated to have “antimicrobial, anticancer, anti-inflammatory, and antiallergic properties in humans.” However, the effects tend to be short-lived as they are volatile compounds in the body. α-pinene and cineole (another phytoncide) work as bronchodilators – making it easier to breathe – especially for those with asthma or other respiratory problems. Cineole is an active ingredient in cold medications because of its ability to thin mucus and relieve coughs. Camphene, another phytoncide common in conifers, reduced wheezing and coughing in one study.
Collectively these compounds promote better circulation and overall lung and heart health. A study compared heart and lung disease deaths in areas where forests were badly affected by Emerald Ash Borer infestations. Those areas with greater trees lost also had higher rates of lung disease deaths (6,112 more deaths) and heart disease deaths (15,080 more heart-disease-related deaths) across the fifteen states studied.
Key Takeaways: Optimizing Your Home Landscape for Human Health
So, how to take advantage of all these health benefits found in nature? If you are fortunate enough to live near protected land (state or national parks, forest service areas, conservation areas), incorporate visits to these areas into your daily or weekly routine. (For our Connecticut readers – check out the Aspetuck Land Trust preserve and trails!) The healthiest change is the one you stick to, so creating a nature sanctuary on your own property is about as hyper local as you can get, all barriers to entry removed!
Work with a landscape designer to develop a plan for your property that is more than a pretty garden viewed from behind a window. Design a landscape that invites you out in its midst, to explore the evolution and notice the intricacies. Practically speaking, we follow these principals:
- Organic Landscapes Only – synthetic additives to the soil do not help cultivate soil microbe communities. In fact, synthetic nitrogen starves microbes of an essential plant-microbe exchange for food and nutrients. You will not reap the benefits of M. Vaccae and other “old friends” in an chemically treated landscape.
- Garden Paths Guide Experience – Create nooks and garden rooms throughout your landscape for spots of contemplation and meditation. A set of sitting boulders or stumps integrates into a naturalistic landscape and invites you to slow down and take it all in. If you have a woodland, consider creating trails through it for your own personal forest bathing loop. Paths also make garden maintenance significantly easier.
3. Evergreens – Evergreen plants like Cedars, Spruces, Conifers, Pines and deciduous Oaks have more Phytoncides and more potential to reap health benefits.
4. Herbs, Vegetables – Incentivize yourself to touch dirt and absorb more beneficial soil microbes by dedicating a spot in your landscape where you will garden, getting your hands in the dirt! Often a vegetable or herb garden is the most motivating for clients – fresh produce to harvest!
5. Keep it Interesting – a garden should be full of surprises; it should be constantly evolving. Design so that each week a new bloom emerges while another turns to seed or berry. Not only will the plant material evolve, but each element is a food source for wildlife. Delight in the hummingbirds, goldfinches, swallowtails and ladybugs that find solace in your landscape.
6. Water Features – Trickling water has psychological and physical benefits, plus it can attract birds to bathe and drink. Create your meditative sanctuary that engages all of your senses.
7. Scented Plants – Speaking of senses, nothing draws people close to a landscape quite like a sweet-smelling flower. Our favorite scented natives include Clethra, Itea, Agastache and Clematis.
Contact us for help designing your dream landscape for mental and physiological health.