TORONTO -- It's no secret that a walk in the woods can be great for boosting your mood.

But a burgeoning group of nature enthusiasts say it can do much more -- including strengthen immunity, lower blood pressure, increase your ability to focus, and ultimately lower health-care costs if done regularly.

This is the forest bathing movement, a growing eco-trend that has nothing to do with water and is all about immersing oneself in the healing properties of trees and plants.

The concept is inspired by the Japanese practice of shinrin-yoku, which translates to "taking in the forest atmosphere."

It involves simply walking -- quietly, slowly and deliberately -- in a forest, and taking in the sounds, scents, colours, forms and general vibe of nature.

Although physical, it's not about exercise. The goal is to wind down and tune in to the natural world, explains certified forest therapy guide Ben Porchuk.

"You really take time to notice things that you take for granted and as you do that, this is where the relaxation comes in," says Porchuk, based in London, Ont.

"You start to breathe more regularly and your cortisol production lowers, which means you feel de-stressed."

He notes that forest bathing is a cornerstone of preventive health care in Japan, where Shinrin-Yoku emerged in the 1980s as stress associated with living in larger cities mounted.

Studies in Japan and Korea found forest bathers after their walks had an increased number of "natural killer cells," immune system cells that combat disease and may even help prevent some kinds of cancer. The researchers believe natural killer cells are boosted when people breathe in organic compounds called phytoncides released by trees.

The data is still largely focused on Japan and Korea, but it's nevertheless spurring similar studies around the world and spawning growth in forest bathing tours, says Amos Clifford, founder and director of the California-based Association of Nature and Forest Therapy Guides and Programs.

There are currently five certified forest therapy guides in Canada -- all of them in Ontario -- but more are on the way, Clifford says from Gort, Ireland, where he was leading a week-long training course.

Canada has another five guides-in-training and Clifford expects up to 15 new recruits will attend a training session next month just outside Toronto.

"We're going to easily triple, maybe quadruple the number of Canadian guides who are certified, probably about seven months from now," says Clifford.

But do you really need to pay a forest therapy guide $50 to take a walk in the woods?

Clifford says these are more than just walks -- they're guided experiences geared to getting stressed-out city dwellers to slow down and connect with their surroundings.

"That's very difficult for most people," says Clifford.

"I can help you get out of your head and into your senses. And through your senses I can help you re-establish an almost kind of remembered way of connecting relationally with the forest."

A session with Clifford can last three-and-a-half hours, but might only cover 400 metres. Guides suggest specific exercises along the way, such as watching leaves sway in the breeze or honing in on the furthest sound you can detect.

Porchuk keeps participants focused on introspection by playing a flute intermittently as they wander. He ends his sessions with a tea ceremony, in which he serves a brew made from leaves and flowers collected during the walk.

"When you move into nature this way and you disengage your mind you get heightened senses," says Porchuk, head of the Canadian chapter of the Association of Nature and Forest Therapy Guides and Programs.

"It just really gives you a sensory experience that you probably haven't experienced since you were a little kid."

The principles behind the movement are fairly well-established, even if the term "forest bathing" is relatively new, says Elizabeth Nisbet, an assistant professor at Trent University.

Nisbet, whose research focuses on the link between nature and health, points to Ontario Parks' "Healthy Parks Healthy People" campaign and the Ontario Mental Health Association's "Mood Walks," which promotes a daily stroll as something that can be as effective in treating mild cases of depression as taking an antidepressant.

In the United States, the Parks Rx program sees physicians actually prescribing time outdoors -- even identifying specific trails and activities tailored to personal needs.

"It doesn't mean that every single person will benefit the same way from nature contact," adds Nisbet, who says ties to nature can also motivate more sustainable and altruistic behaviour.

"But the evidence is slowly building that there's something positive about nature that helps people."

One problem in Canada can be its cooler temperatures, which limit outdoor activity for some. Clifford says forest bathing can be done in the winter, but more data is needed to understand how weather impacts the practice, he admits.

"A disproportionate amount of the research has come out of Japan and Korea and we're just starting to see the same level of research interest just starting to ramp up in many other countries right now, so I would say over the next 10 years we are going to learn a lot," he says.

"It's like 30 years ago if you said: 'I'm a yoga instructor,' people would think, 'Oh, does that mean you're a member of some kind of cult?' We're kind of in the same place. And we're not just promoting and developing a professional practice called forest therapy guiding, we're also creating a whole new class of jobs, a new profession."

For Porchuk, becoming a certified forest therapy guide meant taking a $4,000, seven-day course in California and following that up with a six-month mentored practicum.

He's now ready to help lead a training session on his own turf, set for July 23 in Caledon, Ont.

The curriculum is intense, says Clifford, who devised the association's standards in consult with a physician.

"I'm very interested in having a pretty strong degree of rigour in what we're doing so that this is indeed a credible practice," he says.

"The endgame for me is that it will become normal; an ordinary thing for physicians to refer people to forest therapy experiences. And in order to get there we better be very professional and very science-based."