Time in Nature

Time in nature 

If you want to have better health, something as simple as spending more time in nature, could be an easy option. Known benefits include reducing the symptoms of anxiety and depression, increasing our immune system activation, and lowering blood pressure, and stress hormones. At One5 Health we feel the strong association of time in nature for better health, at all ages is well-established. Studies have defined and measured some of these effects, while others have emerged from reviewing population data, spanning many years. This article explores the science behind how time in nature can be used to treat common diseases, and explains the physical and psychological processes involved.

GENERAL HEALTH

A 2019 study examined data from a diverse adult population in England, finding that people who spent over two hours a week in nature reported better health and well-being regardless of age, illness, mobility factors, and physical activity levels. Benefits were the same for urban or rural residents, with no difference between a weekly two hour woodland walk, or 20 minutes a day in a local park. However, less than two hours a week in nature did not have the same benefits. This study relied on self-reported effects, so we are still lacking data that defines exactly how time nature affects biomarkers. A large observational study assessing population health in European capitals found that people were 40% less likely to be obese if they lived near the greenest part of the city, and a review of American data identified a link between time in nature and healthy aging (longer telomeres). 

ANXIETY & DEPRESSION

A recent systematic review, using data spanning 20 years from high income countries with a diverse population, examined the association between forests or national parks and improved health outcomes for adults. Over half the studies found that anxiety was reduced when people spent time in nature, with some lesser evidence for depression. Interestingly, participants experienced different health effects depending on which department made the referral, highlighting that patient beliefs can influence outcomes. Forest bathing trips were found to significantly decrease participants’ scores for anxiety, depression, and anger, using a validated mood assessment survey. A large review looking at the psychological effect of time in nature found that longer, and more frequent visits to green spaces was associated with reduced risk of depression for urbanites. Interestingly, it identified that time in nature showed strong positive effects for participants with depression, but not for those without. 

BLOOD PRESSURE HEART DISEASE 

Many studies, and reviews have explored the relationship between spending time in green spaces and reduced risk of heart disease. The 2021 review mentioned previously, also examined the physical health effects of time in nature, confirming an association with reduced blood pressure and heart rate, perceived pain, and increased aerobic fitness. A large meta analysis supports this finding. A small study of 60-77 year olds with elevated blood pressure, and self reported stress found that six sessions of forest bathing significantly reduced blood pressure, in hypertension. Weekly sessions were two hours long, with blood pressure and heart rate readings taken before, and after the forest bathing. Interestingly, heart rate was not significantly reduced (only by two beats per minute). An article in the American Journal of Lifestyle Medicine reviewed the current evidence and found a link between visiting or exercising in green space at least once a week for 30 minutes and improved blood pressure. Increasing this to at least three times a week was linked with reduced use of medication. 

IMMUNE FUNCTION

A  2010 Japanese Forest Bathing review tested participants who spent 3 days and 2 nights in woodland for immune function and adrenaline levels, finding a significant increase in NK (natural killer) immune cells, and a decrease in adrenaline. Notably these immune effects lasted for 30 days. They compared this with a two day urban sightseeing trip, which showed no increase in participants immune cell levels. The review attributed the influence on immune function to exposure to phytoncides - essential oils, alpha-pinene and beta-pinene - from the evergreen trees. Another forest bathing study confirmed positive immune effects via white blood cell changes (increasing lymphocytes, monocytes and decreasing granulocytes), while other studies have revealed lowered cortisol levels in males and females, after exposure to nature. A well-known study from 1984 clearly showed that patients in hospital beds with a view of nature had faster recovery time and less pain medication, than patients who had a view onto a brick wall. 

FOCUS AND CREATIVITY

Looking at patterns in nature encourages a switch to an alpha brain state, which is associated with increased relaxation, creativity, concentration and attention. Researchers in Chicago reviewed data of over 500 participants on a reverse order memory test (BDS) before and after exposure to nature, and compared it to urban environments, concluding that performance improved more after time in nature, compared to an urban environment. Effects were increased if the green space was varied, and reduced if it was artificial (virtual reality or photos). Explanations for these changes include; Attention Restoration Theory, the idea that time in nature resets our attention span, and the Biophilia Hypothesis that humans have an innate affinity with the natural world. Studies have demonstrated that living walls can reduce negative thinking by 30% in office workers, and biophilic office designs can promote an alpha brain state increasing creativity and productivity. 

EXERCISE 

Being in nature requires us to be more active to get from one place to another so the link with improved wellbeing and general health might not be surprising. However, studies comparing indoor and outdoor exercise have concluded that participants burn more calories when exercising outdoors, running, cycling or using gym equipment in the park. The reason is unclear, some suggest wind resistance plays a role, or the changing environment helps maintain motivation, or that social connections are increased. One American study even measured an additional weight loss in participants who exercised outdoors, compared to indoors. 

These wide-ranging physiological benefits are broadly attributed to activation of the parasympathetic "rest and digest" nervous system, and an alpha brain state; when a person is alert but not actively thinking about something specific. These have downstream effects to slow heart rate and breathing, relax muscles and increase focus. An extensive Japanese review from 2022 identified that the parasympathetic nervous system is triggered when in nature due to sensory stimulation via sights, sounds, smells, and the physical feel of the environment.

TAKEAWAYS

• For general health benefits spend 2 hours in nature each week - this can be one outing, or regular shorter exposures of 20 minutes a day. 
• For pronounced effects on immune function, adrenaline, and blood pressure. Spend 2-3 days immersed in nature overnight.
• For blood pressure, spend 30 minutes being active in nature 1-3 times per week. 
• Invoke the principles of Forest Bathing; Use all five senses to connect with nature (see, smell, listen, touch), slow down, turn off devices and focus on the environment.
• Spending time near a living wall, cultivating plants in your home, or just looking at nature on a screen has benefits for relaxation, and creativity. 
• Exercise outdoors for additional benefits including vitamin D.
• Potential side effects include anxiety, or fear from being in nature, or irritation from bird noises, or strong winds. 

These sites will connect you with the great outdoors https://www.gojauntly.com/features/walks-near-me

https://www.forestryengland.uk/wellbeing-trails

Kew Gardens holds regular expert-led Forest Bathing sessions https://www.kew.org/kew-gardens/whats-on/forest-bathing

References 

1. Bauer A, White ND. Time in Nature: A Prescription for the Prevention or Management of Hypertension. Am J Lifestyle Med. 2023 Mar 25;17(4):476-478. doi: 10.1177/15598276231165662. 
2. Garibay-Chávez MG, Curiel-Ballesteros A, García de Alba-García J, et al. ‘Effects of Forest Bathing on Blood Pressure and Heart Rate in Older Adults in Mexico’. Forests. 2024; 15(7):1254. https://doi.org/10.3390/f15071254
3. Huynh, L.T. et al. (2022) ‘Linking the nonmaterial dimensions of human-nature relations and  human well-being through Cultural Ecosystem Services’, Science Advances, 8(31). doi:10.1126/ sciadv.abn8042. 
4. Jimenez, M.P. et al. (2021) ‘Associations between Nature Exposure and Health: A review of the  evidence’, International Journal of Environmental Research and Public Health, 18(9), p. 4790.  doi:10.3390/ijerph18094790. 
5. Li Q. Effect of forest bathing trips on human immune function. Environ Health Prev Med. 2010 Jan;15(1):9-17. doi: 10.1007/s12199-008-0068-3. 
6. Nguyen, P.-Y. et al. (2023) ‘Effect of nature prescriptions on cardiometabolic and mental health,  and physical activity: A systematic review’, The Lancet Planetary Health, 7(4), pp. e313–e328.  doi:10.1016/s2542-5196(23)00025-6. 
7. Ogletree, s, Huang J-H, Reif, D, et al ‘The relationship between greenspace exposure and telomere length in the National Health and Nutrition Examination Survey’, Science of The Total Environment, Volume 905, 2023, https://doi.org/10.1016/j.scitotenv.2023.167452.
8. Shao, Yiming & Zhou, Zhenghuan & Ding, et al ‘Psychological Effects of a Living Wall System on Office Occupants: A Comparative Study Based on Physiological Responses’. Buildings. 14. 1981. (2024). 10.3390/buildings14071981. 
9. Stenfors CUD, Van Hedger SC, Schertz KE, et al ‘Positive Effects of Nature on Cognitive Performance Across Multiple Experiments: Test Order but Not Affect Modulates the Cognitive Effects’. Front Psychol. 2019 Jul 3;10:1413. doi: 10.3389/fpsyg.2019.01413. 
10. Summers JK, Vivian DN. Ecotherapy - A Forgotten Ecosystem Service: A Review. Front Psychol. 2018 Aug 3;9:1389. doi: 10.3389/fpsyg.2018.01389. PMID: 30123175; PMCID: PMC6085576.
11. Ulrich, R.S. (1984) ‘View through a window may influence recovery from surgery’, Science,  224(4647), pp. 420–421. doi:10.1126/science.6143402. 
12. White, M.P. et al. (2019) ‘Spending at least 120 minutes a week in nature is associated with good  health and Wellbeing’, Scientific Reports, 9(1). doi:10.1038/s41598-019-44097-3.