Anyone who has walked in a forest knows by common sense the beauty of it. It's why some people choose to live in forests, or next to them, and why other people travel thousands of miles to stand in Redwood forests, or the rain forests of Costa Rica or Ecuador. But researchers in Japan, where the tradition called shinri-yoku, or "forest bathing" is still strong, have discovered some biochemical reasons why. Researchers found that forest bathing optimizes natural immunity, which is important to prevent cancer as well as other chronic illnesses. How does that happen?

When researchers sampled people before and after a 2-hour forest walk, they found all but one forest walker had a 50% higher killer T-cell count. They also had lower blood pressure, and felt calm and clear head
Researchers explained the phenomenon: the forest trees and plants infused the environment with "antimicrobial allelochemic volatile organic plant-derived compounds called phytoncides that exterminate fungi and bacteria". Translation please? Fungi and bacteria can spell trouble for our immune system. Turns out trees don't like them either. Forests trees are often hundreds, if not thousands, of years old. The trees, and other plants, have evolved a protection, a compound they can produce, that kills fungi and bacteria. When you walk in the forest, you breathe and are infused with these compounds. The effect lasts for about 2 months.

Let's say, when you walk in a forest, you bathe in the forest's natural immunity. You're immersed in the forest's phytochemical immune system.

Professor Qing Li, of the Department of Hygiene and Public Health at Nippon Medical School in Tokyo, gave this story to American Scientist writer Anna Lena Phillips. There's more specific info in the article about effects on specific hormones as well, including noradrenaline and DHEA that affect stress response, and adiponectin, lower levels of which is associated with Type 2 Diabetes and obesity. The study appeared in the European Journal of Applied Physiology.