Phytoncides: The Invisible Forest Compounds That May Support Our Health
Released by trees and other plants, phytoncides are fascinating airborne compounds that have attracted scientific attention because of their possible effects on human health and well-being. What are phytoncides, what does the research say, and how do they fit into forest bathing?
In this article:
Why do trees release phytoncides?
Phytoncides are a broad group of volatile organic compounds (VOCs), many of which belong to the terpene family — aromatic molecules with characteristic scents. Terpenes are also major constituents of many essential oils. One example is alpha-pinene, a naturally occurring compound also used in some fragrances and household products.
Naturally present in the air around the trees and plants that release them, phytoncides form part of plants’ chemical defence systems against insects, fungi and bacteria. Plants use these compounds in interactions with pathogens, herbivores and their surrounding environment.
Trees also live within complex ecological communities, respond to threats and interact with neighbouring organisms. Some exchanges within forests are associated with connections involving soil fungi and mycorrhizal networks. Although phytoncides travel through the air, they are one part of the remarkable chemical toolkit used by trees. Volatile compounds can also play a role in plant signalling and communication, as you can read elsewhere on the blog.
Conifers are among the trees known for releasing abundant terpene-rich volatile compounds. Cedars, cypresses, spruces, pines and firs are notable examples. Emissions often increase during warmer periods, while evergreen conifers can continue releasing volatile compounds during winter, when many deciduous trees are dormant.
What might they mean for health?
Because some phytoncides show antibacterial or antifungal activity in laboratory settings, researchers have explored how these compounds contribute to the chemical environment of forests. They are only one part of a much broader forest environment, which also includes cleaner air in many locations, shade, humidity, natural sounds and opportunities to slow down.
This helps explain why forest bathing (shinrin-yoku, closely related to forest therapy) has become so popular. The practice involves spending unhurried time in a forest, breathing naturally and engaging with the environment through the senses. It is the most direct way to experience the natural atmosphere in which these compounds occur.
But what does research suggest about the health effects of forest bathing?
Some answers can be found in a review led by the College of Forestry at Jiangxi Agricultural University in China and published in Environmental Health and Preventive Medicine in 2019. The authors reported findings across several physiological measures, including possible benefits for cardiovascular function as well as hemodynamic, neuroendocrine, metabolic, electrophysiological, antioxidant, immune and inflammatory markers. As with much forest-bathing research, study design and evidence quality vary.
Importantly, the authors were cautious in their conclusions. They also discussed improvements in emotional state, attitudes and subjective feelings among participants in the studies reviewed.
Other possible benefits discussed in the literature include physical and psychological recovery and reductions in symptoms of anxiety or low mood, although forest bathing should not be presented as a substitute for medical or psychological care.
The review concluded that forest bathing may support physical and psychological health, while emphasising the need for stronger empirical studies, better methodology, interdisciplinary research and reduced risk of bias in order to improve the quality of scientific evidence.
Other settings and uses
In most cases, encountering phytoncides naturally means spending time around living plants.
Forest bathing offers the most immersive experience, but botanical gardens, parks and other green spaces can also provide meaningful contact with nature, especially for people living in cities. Even shorter visits to green spaces have been associated in research with aspects of well-being.
Some people also bring more plant life into their homes. Caring for indoor plants can add natural scents and a sense of contact with greenery, although concentrations of forest-derived volatile compounds indoors are far lower than in a woodland environment. The psychological value of tending plants may itself be part of the experience.
Another traditional practice sometimes mentioned involves using fresh conifer branches with hot water to release their aroma. Essential oils from conifers are also used aromatically by some people, but concentrated oils require appropriate precautions and are not equivalent to simply spending time in a forest.
Research into phytoncides adds an intriguing biological dimension to something humans have long experienced intuitively: time in nature can support well-being. These volatile compounds may be one of several mechanisms involved in the effects studied in forest environments.
But the experience makes far more sense when you live it, not only when you read about it. 😉
That is why I invite you to experience forest therapy for yourself: through my forest therapy training at the Ranch in Mouzeil, between Nantes and Angers in western France or my guided walks, to slow down, explore your relationship with the plant world and use trees as a source of sensory experience and metaphorical reflection.
Comments