If there are two things our family loves to do, they’re spending time in Nature and laughing with abandon. Now that we know they’re proven to naturally increase natural killer cells, we’ll love them even more!
Yesterday brought the usual stresses, but regardless of how much school and work we left undone, we were determined to spend the late afternoon and evening in the woods.
My daughter likes to dance no matter where we are. And, like a good yawn, dancing and laughter are contagious. So, before we knew it, we were dancing our way through the trees. The stress melted away to the sounds of our laughter.
Why Laughter May Truly Be the Best Medicine
Researchers at Loma Linda, California’s School of Public Health tested “mirthful laughter’s” impact on immunity.
They had 52 healthy males watch a humorous video for one hour and then measured their killer cells’ activity level.
Before they started watching, it registered 24 percent. By the video’s end, it was around 39 percent – over 60 percent higher simply from a good laugh!
A similar study from the Terre Haute Indiana State University School of Nursing assigned 33 healthy women to watch either tourism or humorous videos.
Only the participants who laughed increased their natural killer cell activity. And the more heartily they laughed, the greater it was. They experienced a dose-dependent response – evidently we can all use a good dose of laughter!
Head Outdoors to Naturally Increase Natural Killer Cells
In this 2019 meta-analysis, Italian researchers reviewed nearly 1,000 published studies on the beneficial effects of spending time in forest environments. Eventually, they concentrated their efforts on 22 that examined forest bathing’s impact on stress levels.
Over 90 percent of the studies showed that after bathing, levels of the stress hormone cortisol were “significantly lower… in forest groups.”
They also compared forest and urban walking. Only forest walking brought an anti-stress response, which began before people even arrived in the woods. It seems the mere anticipation of spending time in Nature lowered cortisol levels!
The meta-analysis’s findings supported this earlier study from Nippon University’s Department of Hygiene and Public Health.
It tracked the NK numbers and activity of 12 healthy men who spent three days and two nights in three different forest fields. All of them took several two-hour walks during the excursion.
When it was over, 11 had a 50-percent increase in their NK levels. And, as we learned yesterday, NK cells do increase with regular, moderate exercise.
Could exercise alone, regardless of the forest setting, have accounted for the increase? That’s the question the Nippon University researchers sought to answer with a second study.
This time, they had a forest and urban group take walks at precisely the same time. The forest group experienced a significant rise in NK-activity. The city walkers had no increase whatsoever.
What’s even more striking is that the Italian study found forest bathers maintaining their lower stress hormone levels for an entire week. And in 2011, another Nippon University study revealed spending time in the forest elevated NK cell activity for a whole month.
What Do Forest Paths Have That City Sidewalks Don’t?
What’s the difference between the forest and the city?
The Nippon researchers suggested it may have been the woodsy smells, also known as phytoncides. Sure enough, testing revealed their positive association with NK cell activity.
And we may be able to enjoy the same benefits without heading to the woods! In 2009, the Nippon team was at it again. They put 12 healthy men up for three nights in hotel rooms with humidifiers releasing hinoki cypress oil vapors.
Their findings: “Phytoncide exposure significantly increased NK activity.”
Whether you spend time in Nature every day, once a week, or even once a month, substantial research has established that you’re helping your immune system’s natural killer cells fight illness – including cancer.
I’ve written this entire post outside, surrounded by trees. It’s still a bit chilly, and I’m wearing a few layers, but the effort has been worth it.
Now it’s time for another family hike, full of dancing, laughter, and drinking in the phytoncide-scented air!