To me, the smell of pine-scented candles is wonderful all the 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 body's natural killer cell activity (1), and actually setting foot out into a forest increases the body's 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)!
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 16th century physician, asserted 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.
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 of all five senses to naturally-occurring stimuli had a direct effect on stimulating the parasympathetic nervous system, resulting in a state of relaxation (6). The multitude of these effects seems 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 only took pumping cypress essential oils into a hotel room to achieve identical effects to those of physically setting foot in a forest (8). But, they are not completely responsible for the health benefits as similar effects were found by having subjects simply look out a window (9) or view images of a forest (10).
Incredibly, we have an expert in forest bathing here in Birmingham at Practice Works! 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, and knowing that my immune system had been rejuvenated.
Long story short, keep those pine and cedar candles burning, just not at both ends please. Sleep is a critical component of a healthy immune system. This summer, 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 immune system!
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2. 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.
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. Jpn. J.Nurs. Sci. 2017, 14, 3–12.