Forest bathing, or Shirin-yoku, lowers cortisol, boosts the immune system and lowers heart rate because it is calming and trees and plants produce phytoncides.
Ever had the urge to take a relaxing walk in the woods or spend a day or two in the forest? Actually you could be helping your health enormously.
Sunlight even encourages the production of anti-depressant serotonin by your gut bacteria (they make approximately 90 per cent of it).
The Infra Red end of sunlight can also directly reverse ‘Hypoxia’. Hypoxia is a state of low oxygen in your body tissues that can cause increased heart rate, a bluish skin, confusion, difficulty breathing and hypoxia is also loved by cancer tumours. Hypoxia is actually promoted by blue light and countered and even reversed by warm light – the red end of the sunlight spectrum being an example. Sunlight, even on the darkest day, reverses hypoxia.
Melatonin, SAD and a walk in the woods
It’s why people who live indoors and people who are highly influenced by blue light (computers, TVs, mobile phones) often sleep poorly and have poor immune systems. SAD is Seasonal Affective Disorder and the Mayo Clinic defines (2) this as ‘Sad is sometimes called Winter Depression. Feeling hopeless, worthless or guilty, it may cause oversleeping, appetite changes, a craving for carbohydrates and increased weight. SAD can be reduced by increasing melatonin, avoiding blue light, switching electronic equipment to night shift and red light and going for a walk in the woods. It’s why ‘Lockdowns’ are terrible for our health.
Of course, you might think that walking in the woods is exercise in the fresh air. Sunlight will increase your vitamin D levels and that alone can reduce depression. Oxygenation and endorphin productions might also be benefits. Endorphins are powerful drugs that we make ourselves when we exercise and they reduce stress hormones (3).
Forest Bathing, Shirin-yoku
But this article is about Forest Bathing, which is done slowly, listening to the birds, a gentle wind rustling the leaves, heightening the senses. A Japanese study on young women showed that Forest Bathing actually did far more – it lowered the activity in the sympathetic nervous system and heart rate. When measure ‘mood’ scores for negative feelings such as tension–anxiety, depression–dejection, anger–hostility, fatigue, and confusion were significantly lower (8).
The Forest lowers your cortisol; stimulates your immune system
But then we come to the trees and plants themselves – almost all trees and plants release phytoncides, essential oils or organic chemicals with protective antimicrobial qualities. Phytonicides also increase NK immune cells which fight viruses. Yes, they stimulate your immune system. And phytonicides have even been found to lower stress-hormone cortisol levels in those people who spend time with them. Lowering your cortisol is one of the main benefits of forest bathing (Shirin-yoku) (4).
Phytoncides actually protects the forest from bugs and disease. The most common are limonene, pinene, myrcene, camphene and sabinene. But there are thousands of them. That’s why you can ‘smell’ the forest, the plants, the pine trees.
Shirin-yoku is not just a walk through the woods. It is a Japanese-originated healing programme. After realizing they had a growing health crisis on their hands in the 1980s, with indoor working and technology becoming the norm, the Government actually created trails, and trained guides to take people through the woods at a slow pace to observe nature and to calm their bodies. It may surprise you to know that there are approximately a thousand research articles on Forest Bathing. And in an Italian meta-analysis (5), where people who participated in Forest Bathing were compared to those left behind in the office, cortisol levels dropped significantly.
Not surprisingly, Forest Bathing has also been shown to reduce blood pressure significantly (6) in a Japanese meta-analysis.
And in a very recent review of all research up to November 2021, Forest Bathing was concluded to be ‘A complementary practice for the promotion of psychophysical well-being, with a positive benefit on individual quality of life” (7).