Twice in the past week I have been left wondering about the positive associations between exposure to nature and our mental and physical health. The first, as I was washing my hands at the allotment where I had been tending to my patch of vegetables. It’s nothing fancy, just some runner beans, different types of lettuce, kale and chard, some courgette and some garlic. But that said, I have noticed an unmistakable and overwhelming difference in my mood cumulatively over the last 4 weeks since I took over the allotment and started to get my hands dirty.

Is it the sense of community? Afterall, we all chit chat as we do the watering in the evenings, we have shared experiences and interests, plus a quiet and unspoken competitiveness as we all judge the quality and symmetry of each other’s patches. Or is there something else at play here?

The second time was when I put my feet up with a cup of tea after a day hike in the bucolic Somerset countryside. Legs mottled red from nettle stings and bramble cuts, again, I couldn’t help but notice my smug level of serenity after 5 hours of solitude, putting one foot in front of another, under blue skies and warm sun.

Biologist E.O. Wilson suggests that these feelings are because of our innate, evolutionary connection to nature. Afterall, it wasn’t that long ago in historical, evolutionary terms that we were wild in nature ourselves. This is known as the Biophilia Hypothesis. It states that we have a deep-seated need for contact with the natural world to thrive both physically and emotionally. This hypothesis argues that our well-being is enhanced by exposure to natural environments, such as plants, animals, and landscapes, which can reduce stress, improve cognitive function, and promote overall health – that our affinity for nature is not merely a preference, but an essential part of our biology that influences our happiness and wellbeing.

So naturally (pardon the pun), the research nerd in me wanted to dig into this a bit further…

“I have noticed an unmistakable and overwhelming difference in my mood cumulatively over the last 4 weeks…since I started to get my hands dirty”

Natural environments reduce stress

Spending time in nature has been consistently linked to reduced stress levels. Nature settings, such as parks, forests, and gardens, provide a calming and soothing environment that promote relaxation and help alleviate stress.

In a Japanese study, the evidence showed that cortisol levels (our stress hormone) are significantly reduced after mild to moderate exercise in natural environments compared to urban environments. Similar studies from Japan report marked reductions in systolic and diastolic blood pressure after participants were exposed to nature – stating that forest walking may lead to a state of physiological relaxation.

Trees positively influence our immune system

Phytoncides are natural chemicals emitted by plants, particularly trees and forests. These volatile organic compounds are part of the plant’s defence mechanism against insects, pathogens, and other harmful organisms. When we are exposed to phytoncides, we can potentially experience several health benefits, including improvements in immune function.

Natural killer (NK) cells are a type of white blood cell that plays a crucial role in our immune system’s defense against infections and cancer cells. Researchers have shown that exposure to phytoncides on days where participants undertook forest bathing activities versus control days can significantly increase the activity of NK cells. They also have anti-inflammatory properties, reducing the production of inflammatory markers in the body.

Phytoncides may be the missing mechanism behind how exposure to nature helps to reduce stress – they have been found to activate the parasympathetic nervous system, which is responsible for the body’s rest and digest response. Activation of this system promotes relaxation, lowers heart rate, and reduces stress overall.

“When we are exposed to phytoncides, we can potentially experience several health benefits, including improvements in immune function”

Protective effects of nature on mental health

A number of studies exist which have tracked and observed large scale population samples and the associations between nature exposure on physical as well as mental health.

Exposure to nature is associated with a lower prevalence of depression – with the optimal dose of 5 – 7 hours over the space of 4 – 5 times per week. In another study, those who were found to spend 5 – 8 hours outdoors over the course of a weekend had much lower odds of being mildly depressed versus those who spent less than 30 minutes or less outdoors.

Time in nature has been linked to increased physical activity, social interaction, and improved cognitive functioning, all of which contribute to better mental wellbeing and a lower likelihood of depression. Nature’s ability to restore attention and promote relaxation is believed to play a crucial role in combating depressive symptoms.

The hygiene hypothesis and soil exposure

The hygiene hypothesis suggests that reduced exposure to microbes in early childhood may lead to an increased risk of developing allergies and autoimmune diseases.

Studies have shown that individuals growing up in environments with higher microbial exposure, such as rural areas or farming communities, tend to have lower rates of allergies and autoimmune disorders.

Exposure to soil has received a lot of attention due to its rich microbial diversity. Soil contains a wide array of microorganisms, including bacteria, fungi, and viruses, which interact with the human immune system when ingested or inhaled. These interactions can modulate immune responses, promote immune tolerance, and protect against the development of allergic and autoimmune diseases.

Several mechanisms have been proposed to explain how exposure to soil can influence human health. One mechanism involves the activation of specific immune pathways that help regulate immune responses and prevent excessive inflammation. Another mechanism suggests that exposure to diverse microbial communities early in life promotes the development of a balanced immune system capable of distinguishing between harmless and harmful substances.

Studies have also explored the role of specific microorganisms found in soil, such as Mycobacterium vaccae, which has been shown to have immunoregulatory effects and may protect against inflammation and allergic responses.

While the research on the hygiene hypothesis and exposure to soil is promising, it is important to note that the relationship between microbial exposure, immune system development, and disease is complex and multifactorial.

“Vitamin N isn’t just a coincidence; there’s real science behind it. Time spent in natural environments offers a respite from stress and promotes deep relaxation”

Nature-based Interventions when working with a Registered Nutritionist

A registered nutritionist will be able to advise and work with you not only on implementing dietary improvements, but we are trained to incorporate lifestyle recommendations into the protocols we design for our clients.

As a keen outdoorist, nature-based interventions play a leading role in the personalised programmes I design for my clients alongside more traditional dietary approaches.

In Summary:

Vitamin N isn’t just a coincidence; there’s real science behind it. Time spent in natural environments offers a respite from stress and promotes deep relaxation. Plants emit phytoncides, natural chemicals that boost our immune system and calm inflammation. The positive impact on mental health can’t be ignored either, with lower rates of depression and enhanced cognitive capabilities with consistent exposure to the outdoors.

So with this in mind, maybe consider adding a solid dose of Vitamin N (Nature) to your supplement stack from now on.

References

Kellert S.R., Wilson E.O. The Biophilia Hypothesis. Island Press; Washington, DC, USA: 1995.

Song C., Ikei H., Miyazaki Y. Physiological Effects of Nature Therapy: A Review of the Research in Japan. Int. J. Environ. Res. Public Health. 2016;13:781. doi: 10.3390/ijerph13080781

Ideno Y., Hayashi K., Abe Y., Ueda K., Iso H., Noda M., Lee J.-S., Suzuki S. Blood Pressure-Lowering Effect of Shinrin-Yoku (Forest Bathing): A Systematic Review and Meta-Analysis. BMC Complement. Altern. Med. 2017;17:409. doi: 10.1186/s12906-017-1912-z

Li Q., Morimoto K., Nakadai A., Inagaki H., Katsumata M., Shimizu T., Hirata Y., Hirata K., Suzuki H., Miyazaki Y., et al. Forest Bathing Enhances Human Natural Killer Activity and Expression of Anti-Cancer Proteins. Int. J. Immunopathol. Pharmacol. 2007;20:3–8. doi: 10.1177/03946320070200S202

Li Q, Morimoto K, Kobayashi M, et al. A forest bathing trip increases human natural killer activity and expression of anti-cancer proteins in female subjects. J Biol Regul Homeost Agents. 2008;22(1):45-55.

Cox, D. Shanahan, D. Hudson, H. et al. (2017) ‘Doses of Nearby Nature Simultaneously Associated with Multiple Health Benefits’ International Journal of Environmental Research and Public Health, 14 (2), pp. 172

Beyer K.M., Szabo A., Nattinger A.B. Time Spent Outdoors, Depressive Symptoms, and Variation by Race and Ethnicity. Am. J. Prev. Med. 2016;51:281–290. doi: 10.1016/j.amepre.2016.05.004

Kaplan R., Kaplan S. The Experience of Nature: A Psychological Perspective. Cambridge University Press; Cambridge, MA, USA: New York, NY, USA: 1989

Kaplan S. The Restorative Benefits of Nature: Toward an Integrative Framework. J. Environ. Psychol. 1995;15:169–182. doi: 10.1016/0272-4944(95)90001-2.

Grönroos, Mira et al. “Short-term direct contact with soil and plant materials leads to an immediate increase in diversity of skin microbiota.” MicrobiologyOpen vol. 8,3 (2019): e00645. doi:10.1002/mbo3.645

DISCLAIMER: The information provided on this website is for informational purposes only and should not be used for diagnosis. It is not intended as a substitute for advice from your GP or other qualified health practitioner.

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