Nuns and natural killers

As I write this, I am sitting in the garden. We have a little oasis of greenery in the middle of the ancient Dutch city that I currently live in. I am lucky enough to reside in an apartment situated in a renovated Beguinage, or 'begjnhof' - one of the many architectural complexes of this sort that are scattered throughout the low countries, and characterized by private houses surrounding an inner courtyard with a communal garden. Beguines, the women who lived in these complexes, were women who devoted themselves to prayer and their community, without taking formal religious vows. Like nuns, but less regulated and with more freedom and self-direction. The Beguines were indeed religious and humble, and took vows of chastity while they lived in the Beguinage, but they were also free to keep their worldly possessions, go out into the city on their own and when they wished, and to leave more permanently at any time. As I read about this order, they seem like very smart women. In the 13th through 16th centuries, when the Beguine order was most active, life didn't hold much promise for women. But by coming together and supporting each other, the Beguines found a way to make the most of their life. As is written on Wikipedia, "Beguines seemed to enjoy the best of both worlds: holding on to their property and living in the world as laypeople while claiming the privileges and protections of the professed religious."

Of the many scattered pieces of their legacy, the one that I get the most out of personally is this almost enchanted garden that my apartment faces on to. It is a lush green space in the middle of the city hustle and bustle. As I write, the sunlight dapples through the leaves of two ancient trees to my right, and my neighbours pick leafy greens from their garden plots to my left. I can hear the breeze whispering through the branches, and as I listen I can feel the tension of life as a PhD student leave my neck and shoulders.

There is no question about the fact that modern living is stressful. I cannot say for sure if it is more stressful than life in previous centuries - but I imagine that living as a woman in the middle ages wasn't a piece of cake. Nonetheless, modern life is undoubtedly stressful in different ways than life pre-technology. Now, there is no escape from our electronics. A couple of years ago, my phone was stolen, so I went without one for three months until I could pick up a second-hand one from my Mum. At the time, I was complimented for my fortitude in enduring so long without access to WhatsApp, Instagram, SnapChat, Facebook Messenger. I found this reaction understandable, but also strange. For me, it was amazing to be able to say to people that they couldn't get in touch with me at any moment of any day. That they'd have to wait. Honestly, I often miss being unreachable.

This constant reachability, combined with the disruption of our circadian rhythms by using artificial light, moving towards technological rather than natural leisure activities, and all the other downstream effects of our increasing embracement of and dependence on technology, has led to exacerbation of humanity's collective stress. You've probably noticed it too. So many people have tentatively and half-ashamedly commented that being forced to slow down during the COVID-19 lockdown was a blessing in disguise.

But how does all of this connect with Microbial Mondays? Well, stress has a heavy impact on the immune system. We've known for a long time that chronic stress is especially nasty, disrupting immune signaling and eventually leading to a sort of exhaustion of your immune cells. Small bursts of stress are fine - this tells your body to be on high alert. But when stress is extended endlessly, your body is also on high alert endlessly. Eventually, something's gotta give. And oftentimes, what gives is your health. However, this is by no means inevitable.

A couple of months ago, I ended a Microbial Mondays post on diet and the immune system with the paragraph, "That's all for this time. Until next week, I challenge you to take advantage of the long summer days and get outside! It's good for your immune system." Today's post is in response to a question that Michael sent me that week. He asked, "How?"

As well as the benefits of clean fresh air and, for kids, immune system training by exposure to harmless dirt and bugs and other messy outdoor stuff, which is thought to help prevent allergy development, there is something more at play. This something more can be summed up by the term, "Nature Therapy".

In recent years, research stemming primarily from Japan, where people have a long tradition of connection with nature, has indicated that spending time in nature can improve immune system functioning, acting as a sort of preventative medicine. For a scientist like me, nature therapy seems at first tricky to define, because it will not provide highly specific effects. There is no targeting protein X for effect Y, like there is with empirically tested pharmacological treatments. But, just because it is trickier to study within the lens of Western medicine, doesn't mean we should throw it by the wayside.

In particular, a type of nature therapy called "forest bathing", (shinrin-yoku in Japanese), seems to promote health. Several different benefits of forest bathing, or mindfully taking in the atmosphere of the forest through all our senses, have been reported. For many years, there have been reports that forest bathing decreases circulating stress hormones, pulse rate and heart rate variability, and blood pressure in young people. More recently, two studies on hypertensive middle aged men showed a reduction of heart rate, and the stress hormone cortisol, after walking in a forest as compared to walking in an urban area (here and here). Those results were also replicated with middle aged women. In terms of the immune system, the reduction in cortisol is notable. The relationship between cortisol and the immune system isn't fully understood yet, but we do know that there is feedback between the immune system and the body's stress system, and that major disruptions in the stress system seem to promote development of, or worsen, autoimmune disorders and cancers.

Interestingly, the benefits of forest bathing don't even stop there. Multiple studies (like this one and this one) have also shown that natural killer cell activity increases with forest bathing - and that these cells' activity even increases with each additional day of the nature therapy. Natural killer cells are cells of the innate immune system - meaning they respond quickly to signs of problems, and don't need extensive immune system training to do so. As the name implies, these cells are the James Bonds of the immune system. They act quickly and independently to target and kill virus-infected or cancerous cells. In line with this, those same scientists also found that forest bathing increased the amount of cancer-controling proteins produced by your body.

These results, that natural killer cells became extra James Bond-y after forest bathing (I guess even Bond needs a break once in a while), were shown in both males and females, and the benefits seemed to last for up to a month. Interestingly, the authors of these studies even found a specific substance derived from the forest that promoted the NK cell activity. Aromatic volatile (i.e. really smelly) substances called phytoncides that are produced by the hinoki cypress alone were able to give a kick-start to natural killer cell immune activity. So, that delicious, fresh smell of trees? Your immune cells like it too.

To sum up, based on the current literature, it seems that forest bathing helps with not only feeling more relaxed, but regenerating your immune system to some extent. However, there is still not a full understanding of this phenomenon, which is complicated by differences in methodology by the researchers, individual differences in participants, and even the types of forest used for this type of nature therapy.

We can't put these studies in a petri dish, so the relationships between the many variables are more difficult to tease apart. But for myself, I've read enough. I will continue to bathe in the dappled light of the ancient trees in my Beguine binnenhof.

Until next time, let your immune system revel in the dappled light filtering through the leaves...

~ Alex