Time in a wild setting, studies indicate, unleashes a powerful cascade of hormonal and cellular responses. Salivary cortisol, for example, dropped on average 13.4% when subjects simply looked at a forest setting for 20 minutes. Pulse rate, blood pressure and sympathetic nerve activity decreased as well. Even more remarkable is the significant – and lasting – impact on so called “natural killer” cells, powerful lymphocytes known to fight off infection and attack cancer growth. A longer three day trip in the forest with daily walks resulted in a 50% rise in NK activity as well as an increase in the number of NK cells! The forest exposure, researchers found, also resulted in increased anti-cancer protein expression. Tests further indicated a rise in the levels of intracellular granulysin, perforin, and granzymes A/B and a decrease in urinary adrenaline. What’s perhaps most surprising is this: subjects who participated in this series of forest bathing trips showed immune NK benefits that lasted more than a month.