Exposure to nature strengthens your immune system, activating natural killer cells that help protect you from cancer and infection. Contact with soil has been clinically shown to improve the composition and diversity of your microbiome. In this episode we explore forest bathing and the scientifically proven benefits that exposure to nature has on your gut and overall health.
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On today’s show, I’m here in the Gutbliss studio with my good friend, Doug Barker. Doug is president of a management consulting business, but his true passion is gardening and nature. He is what we would call a plant nerd. He was chief information officer for the Nature Conservancy, the world’s largest conservation organization, is vice chair of the board of the American Horticultural Society, and he’s a founding member of the Rock Creek Conservancy here in DC. Doug, welcome to the podcast.
Thank you. It is really great to be here.
So let’s dive right into it. Tell us about the impact gardening has had on your own health and well-being.
So time in my garden, and that could even just be houseplants, or out in my garden, just makes me feel better physically and mentally. I am more aware of things. I’m more present. I eat better. I sleep better. I just feel better about my life and planet Earth.
And were you always interested in plants? Because you’re not just sort of a part-time naturalist. I mean, you’ve worked in the conservancy world. So tell us about how you got interested in it.
Well, even growing up both of my parents were always big nature lovers and gardeners, and my grandparents were big gardeners, so I grew up around it, but I didn’t have a green thumb to start with. I remember my first houseplants I immediately killed them I did not know what I was doing, and it takes a while to kind of build up that knowledge and that confidence, but I’ve always just felt at home with plants. Plants are just, they’re just wonderful. They’re wonderful to eat, they’re wonderful to touch, they’re wonderful to grow, and they respond to us in such beautiful ways.
Well, people who are listening to this can’t see it, but you and Sam have the most beautiful home, and the backyard is like Shangri-La out there with the plants. I’m glad you mentioned about not having a green thumb in the beginning because every time I look at my little lemon tree which is a year and a half and barely has leaves much less lemons and I look at your lemon tree full of these huge ripe beautiful lemons I hope that there is still hope for me.
There is a lot of hope for you Robynne. My tree has gone through a lot of different iterations and sometimes not so healthy. And the thing that I love about gardening is you can just get deeper and deeper into it, both the science of it, but then also the art of it. And there’s just always more to learn. It’s just a beautiful thing. It really gets you in sync with the seasons and with your own circadian rhythm and with your own daily routines.
Well, I love that you mentioned the science of it because historically humans have interacted with soil in every culture, and soil is one of the main sources of our microbes. We get our microbes, those of us who are lucky enough to be born vaginally, in that initial passage through the birth canal, the head of the baby turns posteriorly to swallow a mouthful of microbes, and those microbes become the founding species of our own microbiome. But where else do we get microbes beyond that initial first step? It really is through interaction with nature and with soil. And there’ve been several studies that show that the microbiome of people who garden is different, and I dare say superior. There’s more diversity generally in the microbiome and these detectable changes in the microbial community. And the experiment has been done where you take somebody who is sort of a city dweller, doesn’t have much exposure, and then you expose them, and in just two weeks, you see significant changes in the microbiome. So there’s a real science to it. It is actually physically changing us.
That makes a lot of sense. I think that any time that I’m in nature, I realize that I’m interacting with the microbiome and just with all the bacteria and everything out there, both in terms of touching it with the soil, but also breathing it, tasting it, smelling it. It’s just the thing that was a real sea change for me was when I realized that most of what is our human body is actually not made up of human cells. I think I was reading, what, 43% of the cells in our body are actually not human? They’re microbial.
And the number is actually greater. So we have about 23,000 genes and about 3.3 million microbial genes, and that number is growing. And in terms of the ratio of human cells to microbial cells, we’re outnumbered somewhere between two to three to one. So we have two to three times as many microbial cells in our body as human cells. We’re just the hive. And we are animated by our microbes. They’re like the bees who are in there making all the stuff. So I want to talk a little bit about something that you and I are huge fans of, which is this concept of shinrin-yoku, forest bathing. Tell us a little bit about forest bathing.
Shinrin-yoku, forest bathing, it started in Japan, but now it’s become popular the world over. The Norwegians also have their corollary to it, but what it is, it’s not literally bathing in the forest, it is full immersion in the forest. All of your senses engaged. Don’t bring your cell phone, don’t bring anything else. Get quiet, get present, and start to engage your senses. What are you seeing? What are you smelling? Can you walk up and touch a tree and get in touch with it? Feel the soil.
And you know, the studies show, because we know intuitively that this stuff is good for us, but we have this scientific foundation of information that really supports it. And spending time outside in fresh air, what you described, surrounded by trees and nature, forest bathing, lowers blood pressure. It leads to a healthier cardiovascular system. It decreases anxiety, depression, fatigue. It enhances feelings of well-being, happiness, creativity. And it is also clinically shown to improve recovery after illness. And so this isn’t just, you know, this sort of hippie sense of, I feel better. We know that spending time in the woods confers benefit to us by increasing the activity of natural killer cells in our immune system. And those are cells that not just fight infection, but they actually fight cancer. And in the sort of original forest bathing study that you and I have talked about, you knew that just a two-hour walk in a forest park in Tokyo showed a significant drop in the stress hormone levels and other health benefits in the study participants that lasted a full week. So just think about that. I mean, a two-hour exposure. And these were city forests. These weren’t, you know, people weren’t driving hundreds of miles away, can have benefits that last up to a few weeks. It’s pretty astounding. It really is, and it’s accessible to all of us.
We’ve all got parks nearest or other places we can go to be in nature. I did a little mindful walk in the park the other day in Rock Creek Park. It was maybe only about 45 minutes, but when I got home, I just felt my breath was deeper and fuller and better. I felt calm. My whole nervous system was kind of like rewired, and I felt so alert, but at the same time relaxed. It was just a presence that was a beautiful thing.
And you’re also getting from a sort of health point of view, you’re also benefiting from these phytoncides in plants which are natural oils that plants produce to defend themselves from bacteria and fungal organisms etc. And they’re in a lot of wood essential oils and they’re in high concentrations in places like Rock Creek and other forest environments. And again, inhaling those phytoncides, you talked about that feeling you had when you come home, again, improves your immune system, reduces stress, lowers blood pressure and heart rate, lowers cortisol levels. And again, these benefits can last for weeks at a time. So phytoncides are such an important part of arming our immune system. When we come back, we’re going to be talking about the open air factor and how being outside can protect you from infections.
We are back with my guest and friend, Doug Barker, plant nerd, talking about forest bathing and the open air factor. So in the Spanish flu epidemic of 1918, there was an observation made about recovery, and the observation was that the enlisted soldiers who were recuperating inside the hospital with recirculated air, they had a higher mortality of 40%. And it was that exposure to the open air, what is called the open air factor, that’s credited with that dramatic decrease in mortality, 13% versus 40% for recovering outside versus inside. The open air factor is defined as the germicidal constituent in outdoor air that reduces the survival as well as the infectivity of pathogens. It can protect you not only from harmful bacteria like E. coli, but viruses like influenza and SARS-CoV-2. And we have seen similar numbers during this last pandemic of not just less infectivity outside, but also better recovery. So this exposure to open air was actually standard treatment for infectious diseases like tuberculosis before we had antibiotics. It’s pretty powerful medicine. And you have a practice, Doug, of how you bring the outdoors into your home that I’d love you to tell folks about.
Oh, absolutely. It’s one of my favorite things to be doing. So part of it is, you know, a lot of potted plants. I’ve got a wonderful Meyer lemon tree, a dwarf one, and right now, even though it’s a little tree, it’s probably got about 60 lemons on it. But in addition, there’s just so many different ways. One of them is, you know, we’re gearing up for the holidays now, and so I’m decorating the house and hanging the greens. For some people, that means pulling out boxes of plastic fake greens, which can give off microplastics and other things that I can’t imagine inhaling would be very healthy for us. But in my case, we’ve got pine roping and other fresh greens that I’m cutting and putting on the mantle and around the mirrors, just smelling those beautiful evergreens, the cedar and the other things. They smell great. And now based upon what you’ve shared today, I’m realizing they’re doing more than that. They are helping me fundamentally be healthier, fight disease, and have a good life.
Yeah, those natural killer cells. Your natural killer cells are thanking you for hanging all those greens. Give us a couple other of your big tips, because that was a really helpful one, decorating, whether it’s a holiday season or just regular everyday decorating. You don’t have to go out to the plant store and buy a plant. You can literally get some cuttings from your garden and, you know, stick some leaves in a vase. That’s totally acceptable. Or put some on your mantel. Give us some other tips for how people can bring a little bit of nature inside.
Well, I think when the weather permits and it’s nice outside, opening up a window is great. And particularly, we’ve got birdsong or other things out there to listen to, but also just that fresh air. Houseplants can be so rewarding. And you can start small. Just buy a houseplant, buy something that is low maintenance, and really learn what it wants. And when you start to listen to plants, and you start to pay attention to them, and they’ll tell you. They’ll say, I need water, or you’ve given me too much water, and when you start to listen to that language, you really get to a much deeper, more meaningful place with all of life.
I’m definitely an over-waterer, too much water. I kill plants with too much water. I’m sure for different plants it’s different, but you want to test the soil. And actually touching the soil is great because again, we have scientific evidence that exposure to soil, not just being out in nature and smelling and seeing and hearing and tasting, stuff comes into your mouth, but touching soil can really transform our microbiome. And we know that when we look at people in urban environments, for example, in cities, where there’s a lot of glass and concrete, their skin is colonized with different organisms and more Staph aureus that’s associated with eczema versus people in more rural communities who have more direct exposure to soil. And they tend to have different skin microbiome and less eczema and topical allergies. So touching the plants, touching the soil, feeling for moisture levels, all of that is actually really good for you.
Yeah and that’s one of the ways you can pay attention to your house plants. You stick your finger in the soil to see if they need watering or not. Now Doug, you have a couple organizations you want to tell us about when we come back.
We are back with my friend plant nerd Doug Barker to talk about how we can bring a little bit more of the outside into our lives and grow a good garden. So Doug, there are a couple organizations you wanted to tell us about.
Yeah, the first is the American Horticultural Society. It’s a wonderful organization and membership is reasonably priced. And once you’re a member, you get a great magazine, the American Gardener, but in addition you get access to over 300 public gardens throughout the United States. You either get free admission or very discounted admission. It’s a huge benefit and there’s all these beautiful places in all 50 states.
Does it include anything here in D.C.?
It does include several things here in D.C. I think the botanical gardens, those might be free. I’d have to look to see exactly, but it does. It’s throughout the whole country.
I’m obsessed these days with Longwood Gardens. I haven’t been yet, but I hear it’s absolutely beautiful, about two and a half hours from D.C.
Longwood Gardens and all the gardens up in that part of Pennsylvania and Delaware, there’s so many beautiful gardens up there. Chanticleer is another one that is just exquisite up there near Longwood.
I’m going to go do some forest bathing up there. Clothed. Make sure you’re clothed, people. Do not be walking around in the forest with no clothes and claim that the Gutbliss podcast told you to do that. So fully clothed. All right. What is the other organization you wanted to tell people about?
It’s one here in D.C. It’s called City Blossoms, and it’s really geared towards getting kids involved in kid-driven gardens. So they cultivate the well-being of communities through engaging kids in gardening. And if you’ve got your own children or your grandparent or an uncle or aunt or uncle, in my case a great-uncle, getting engaged in gardening with kids is so much fun. Their whole sense of discovery and wonder and everything else. It’s just like, think of how many classrooms they’ll give kids, you know, something like a sunflower seed and the kids will watch it sprout and begin to grow. It is really miraculous. It’s just a beautiful way to do it. It kind of reminds me, too, to really put on your children hat anytime, even if you’re just all adults. Have fun with this. I mean, gardening should be fun. Enjoy it.
And kids need exposure to dirt. I remember when my daughter was little, if she was at summer camp and she came home and she didn’t look dirty, I was pissed. I was like, what have you been doing? Are you just sitting inside with crayons? You need to be outside getting dirty! She loved Calleva summer camps here in the DC, Maryland, Virginia area and she would come home filthy. There’s a farm camp she went to. So kids are supposed to be getting out there in the dirt. I want to give a shout out here to Richard Louv’s excellent book, “Last Child in the Woods: Nature Deficit Disorder”. It’s not just the screens, the fact that kids and adults are spending more than 12 hours a day on screens is the latest statistic. It’s the fact that they’re not outside in nature. We need this exposure. We need it for our immune system. We need it for our microbiome. And kids need it for their cognitive development. So I love this organization. Thanks so much for telling us about it. Any final messages for folks about how to grow a good gut garden?
I think find your bliss with it and start small and have fun. And if it’s one house plant or just one walk in the city park, whatever it is, just get started and make time for it in the middle of the day. You’ll be happy you did.
I love that. Thanks so much, Doug. Thanks for joining us.
My pleasure. It was great to be here.
I want to leave you with three takeaways about growing a good gut garden:
1) Exposure to nature strengthens your immune system, activating natural killer cells that help protect you from cancer and infection.
2) Contact with soil has been clinically shown to improve the composition and diversity of your microbiome
3) If you can’t get outside in the woods, consider bringing the outside in with a house plant
So that’s it for this episode of the Gutbliss Podcast on how exposure to nature improves your gut and overall health.
Coming up next week on the Gutbliss Podcast: Getting regular, in the gym and in the bathroom!
