Forest Bathing Has Immune Health Benefits

Written by: Anna Andersen, 4Life Senior Manager of Research and Development

Have you ever taken a walk in nature and felt refreshed, energized, and calm? It seems self-explanatory, but there’s actually quite a bit of science behind why. Doctors have been recommending spending time in nature to improve health for centuries. Hippocrates himself even said, “Nature itself is the best physician.”¹

What Is Forest Bathing?

Scientists from around the world have explored “Shinrin-Yoku” or “forest bathing,” the practice of spending time in nature to improve health, for years. Forest bathing usually involves spending time in the forest, but you can experience benefits even by observing virtual nature environments after as little as 15 minutes! Many scientific studies throughout the years demonstrate the many benefits of spending time in the forest.

Health Benefits of Forest Bathing

Improves Stress and Mood

Research shows that forest bathing can improve many health markers in the human body. A 3-day forest excursion can lower stress levels (as measured by blood pressure, heart rate, and cortisol levels) and boost mood, compared to spending time in urban landscapes.² Forest bathing also may improve mental health. Study participants also reported feeling more refreshed and relaxed after spending time in the forest.²

Decreases Inflammation and Blood Pressure

Another study demonstrated a positive effect on blood pressure after a seven-day trip through the forest. Markers of inflammation such as interleukin-6 and markers of disease such as angiotensin were positively affected after the seven-day trip. This same study even tested the air quality in the forest versus an urban landscape and found much cleaner air in the natural environment. This may contribute to reduced inflammation and better heart health.³

Improves Sleep Quality

Interestingly, a forest environment can even improve aspects of health such as sleep,⁴ and another study in young men in Japan showed a positive effect on depression and serotonin, which is a neurotransmitter involved in positive moods.

Supports Brain Health

Spending time in the forest can also have some beneficial effects on the brain. Walking in nature or even just viewing pictures of nature can improve focus and cognition.⁵ One study done in elderly people showed that a forest healing program helped decrease risk factors for cognitive decline due to dementia.⁶

Increases Relaxation

An interesting feature of virtual forest bathing is the ability to provide pain relief and increase relaxation. In a study done last year, mobility-impaired and low-energy participants reported that viewing pictures and videos of forests improved their quality of life in a number of ways.⁷

Improves Recovery

A trip to the forest can also hasten recovery from physical injuries. In one study, participants spent time walking in the forest and their chronic neck pain was rated on a ten-point scale, and the participants showed improvement in pain levels after walking in the forest. Participants who also did stretching exercises showed improvement in their range of motion and the number of trigger points in the neck was reduced.⁸

Forest Bathing Benefits on Immune Health

All these effects are amazing, but there’s one more we’d like to focus on today: how forest bathing affects the immune system! Forest bathing has been shown in several studies to positively affect the immune system.

One study performed in Hungary took blood samples from people who walked in the forest in late spring for two hours. The scientists measured several immune system markers, including CD69, granzyme B, NK cells (Natural Killer cells), and many more. Several of the markers of a healthy immune response improved after the forest walk.⁹

In another study, participants spent three days and two nights in a forest setting, and their blood was collected at different time points. The NK cells were extracted from the blood and tested. The percentages of lymphocytes and monocytes (types of white blood cells) in the blood increased! NK cell activity was also measured, and it improved after the forest trip.⁹ The most interesting result of this experiment is that NK cell activity was still elevated for up to 30 days after the forest trip!¹⁰ That means longer-lasting immune support, all from a few days in the forest!

Phytoncides Stimulate NK Cells

But we can be even more specific! What is it about the woods that helps boost the immune system so well? Trees have essential oils called phytoncides that can cause some specific effects. In an in vitro study, these tree wood essential oils were used to stimulate NK cells to fight immune system threats. These phytoncides stimulated the NK cells to have a greater cytotoxicity against the target cells and increased some markers of immune system activity called perforin, granzyme A, and granulysin. Even damaged NK cells in this study showed a restorative effect from the wood essential oils. ¹¹

Forest bathing has been shown to improve immune system function. A literature review done in 2021 reviewed thirteen separate studies that tested the effects of forest therapy on the immune system, some of which we’ve mentioned above. Other studies showed that NK cell activity increased or other immune system or stress markers were improved. ^{12 13, 14, 15, 16}

Conclusion

Being in the forest or even viewing pictures or videos of the forest or nature can be very beneficial to many aspects of your health, especially your immune system. The next time you get the chance to go for a walk in nature or go camping, know you’re doing something amazing for your health as well as having a great time.

Sources:

1. https://sitn.hms.harvard.edu/flash/2021/nature-itself-is-the-best-physician/

2. https://www.tandfonline.com/doi/abs/10.1080/02827580902903341

3. https://www.sciencedirect.com/science/article/pii/S0914508712001852

4. https://www.jstage.jst.go.jp/article/ehpm/27/0/27_22-00136/_pdf

5. https://thehealthsciencesacademy.org/wp-content/uploads/2017/05/The-Cognitive-Benefits-of-Interacting-With-Nature_The-Health-Sciences-Academy.pdf

6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9027266/

7. https://www.mdpi.com/1999-4907/14/5/1033/

8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4720772/

9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7923773/

10. https://journals.sagepub.com/doi/pdf/10.1177/03946320070200S202

11. https://www.tandfonline.com/doi/abs/10.1080/08923970600809439

12. https://www.sciencedirect.com/science/article/abs/pii/S1550830712002571

13. https://www.sciencedirect.com/science/article/abs/pii/S1618866715000114

14. https://www.sciencedirect.com/science/article/abs/pii/S1876382015300111

15. https://www.besjournal.com/fileSWYXYHJKX/journal/article/swyxyhjkx/2016/3/PDF/20160307.pdf

16. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4808918/