Forest Bathing

To me, the smell of pine-scented candles is wonderful all year round – not just at Christmastime. Apparently, I am far from alone in my scent preferences; they are universal and their health benefits are backed by numerous studies! Known in the medical literature as “forest bathing,” what is really just time out in nature is well-studied and has a multitude of benefits. Simply viewing a photograph of a forest increases your natural killer cell activity¹ and actually setting foot out into a forest increases your natural killer cell activity AND absolute numbers!² As if this situation could possibly get any better, changes occur within minutes, and even just the one trip out into the forest can cause this effect to last for 30 days!³

History

Cyrus The Great built lush green areas into the capital city of Persia 2500 years ago to improve health and to increase the sense of “calm” in that busy metropolis. Paracelsus, the great physician asserted in the 16^th century that “the art of healing comes from nature, not from the physician.”⁴ Doubtless this is why the city of Savannah, Georgia was laid out with green-space squares, that New York City has Central Park, and that San Antonio, Texas has the River Walk.

Benefits

Despite this knowledge existing in unofficial form for millennia, forest bathing has not (as yet) made its way into our medical armamentarium. As recently as 2021, a meta-analysis (a study of studies) found that forest bathing had benefits to the cardiovascular system and immune systems, caused decreased symptoms of both depression and anxiety, as well as decreased stress levels overall.⁵  Kaplan found that an exposure to naturally-occurring stimuli (all 5 senses) had a direct effect on stimulating the parasympathetic nervous system, resulting in a state of relaxation.⁶ The multitude of these effects seem to come from the inhalation of what one writer appropriately termed “quasi-pharmaceuticals.”⁷ These are volatile aromatic compounds such as alpha-pinene and limonene that produce the wonderful scent of pines that we might associate with being out in nature. Indeed, it took only pumping cypress essential oils into a hotel room to achieve identical effects to those of physically setting foot in a forest.⁸ But the scents are not completely responsible for the health benefits, as similar effects were found by having subjects simply look out a window⁹ or view images of a forest.¹⁰  How fascinating is it that what is part of the tree’s immune system helps strengthen our own immune systems?¹¹

Simplicity

Incredibly we have an expert in forest bathing at Practice Works medical co-working space in Birmingham! So I went for my first “forest bathing” dip at the Birmingham Botanical Gardens and found that the structure provided by a guide (in this case Anne Markham Bailey) for that first experience was immensely helpful. Not only did I get to enjoy the Gardens, I left with a greater sense of calm and gratitude, with the happy knowledge that my immune system had been rejuvenated. Not only is this free to all, it can be done alone, in groups, in the city, out of the city – how many other medical “treatments” can boast of this??

Time in nature, we need more!

Long story short, keep those pine and cedar candles burning, just not at both ends please. Sleep is a critical part of immunity. Sleep generates melatonin, which is the only intra-mitochondrial antioxidant (that I am aware of) that we can generate by our own actions.¹²  More on that topic later. This coming summer, please take advantage of the many opportunities we have in Birmingham, from the pine-tree-surrounded Pinson Valley Recreation Center track to Oak Mountain State Park, and know that you are both enjoying nature and priming your health!

References:

1. Li Q, Nakadai A, Matsushima H, et al. Phytoncides (wood essential oils) induce human natural killer cell activity. Immunopharmacol Immunotoxicol. 2006;28(2):319-33.
2. Ibid.
3. Li, Q., Morimoto, K., Kobayashi, M., et al (2008). Visiting a forest, but not a city, increases human natural killer activity and expression of anti-cancer proteins. International journal of immunopathology and pharmacology, 21(1), 117–127.
4. Williams, F. This Is Your Brain on Nature. Natl. Geogr. 2016, 229.
5. Stier-Jarmer M, Throner V, Kirschneck M, et al. The Psychological and Physical Effects of Forests on Human Health: A Systematic Review of Systematic Reviews and Meta-Analyses. Int J Environ Res Public Health. 2021 Feb 11;18(4):1770.
6. Kaplan, R.; Kaplan, S. The Experience of Nature: A Psychological Perspective; Cambridge University Press: Cambridge, UK, 1989
7. https://www.prevention.com/life/a20461067/how-nature-naturally-boosts-your-mood-and- happiness/(accessed 5/31/22)
8. Li Q, Kobayashi M, Wakayama Y, et al. Effect of phytoncide from trees on human natural killer cell function. Int J Immunopathol Pharmacol. 2009 Oct-Dec;22(4):951-9.
9. Ulrich, RS. (1984) View through a window may influence recovery from surgery. Science 224(4647):420-427.
10. Tsutsumi, M.; Nogaki, H.; Shimizu, Y.; Stone, T.E.; Kobayashi, T. Individual reactions to viewing preferred video representations of the natural environment: A comparison of mental and physical reactions. J.Nurs. Sci. 2017, 14, 3–12
11. Riedlmeier M, Ghirardo A, Wenig M, et al. Monoterpenes Support Systemic Acquired Resistance within and between Plants. Plant Cell. 2017 Jun;29(6):1440-1459.
12. Claustrat B, Leston J. Melatonin: Physiological effects in humans. Neurochirurgie. 2015 Apr-Jun;61(2-3):77-84.