Take the Green Pill

It's good for your health

I’ve been feeling under the weather for about two weeks. I’m not looking for sympathy. I’ve identified the cause. Since the beginning of October, it has rained almost non-stop. For me, this is less time outdoors with nature, no river swimming (too dangerous), little gardening, fewer walks, and more time in front of a screen.

My time beneath the oaks is medicine and I’m missing my daily dose.

Trees are good for your health, so much so, there is little from contemporary medicine’s potions and pills to compare. Whether you’re feeling blue or have something more serious affecting you, a couple of hours with trees this week is the best pill you can take. Unless you have pollen allergies, you don’t need to worry about toxicity, side-effects or equipment. You don’t even need to exercise. You can sit as still as you like for that couple of hours.¹

Sycamore Gap Tree by Clementp.fr - Own work, CC BY-SA 4.0,

In a review of more than 200 studies into the relationship between urban trees and health, green spaces are associated with a lower prevalence of asthma in children and lower incidence of lung cancer.

The benefits however, go well-beyond good respiratory function. The same study found that trees decrease the chances of heatstroke and heat-related morbidity. Leaf pores release tiny puffs of water vapour, cooling the air beneath the canopy. Tree canopies reduce UV exposure, improve cognitive function and reduce stress-related symptoms and depression.

Some of the effects are indirect. For example, the higher the urban tree cover, the higher are levels of commuter walking and cycling, more recreational walking, and more children’s play. Correspondingly, a lower prevalence of obesity was found in neighbourhoods with good tree canopy.

In a Hungarian forest, two separate studies discovered increased production of Natural Killer (NK) cells. This means green spaces boost immune system function. If you plan a visit, May is better than January to take a break from it all. This boost to the immune system works better in Spring. Perhaps not so surprising a result?

However, this may surprise you: the incidence of lethal prostrate cancer is lower when people live near urban green spaces.

And if you’re suspicious about self-reports of good health and well-being after time spent in the forest, this can be accounted for. Time with greenery raises serotonin levels which correlate with self-reports of improved mood.

While the health benefits of being in green spaces, being able to see greenery from your place of work, and taking a walk in a forest of trees, are positive in a wide range of studies, they are complicated by other factors. For instance, some trees emit pollens which exacerbate asthmatic conditions and other results are complicated by age and gender. Some studies are not generalisable as their focus is highly specific.

There are more outstanding questions arising from the results than answers. So don’t dispose of your doctor’s pills in favour of the green pill, but certainly considerate it as a desirable boost.

Why are the effects so positive?

It has been argued that our affiliation with nature is grounded in our evolutionary past. Urban living is only a recent phenomenon, one for which we are ill-equipped, and therefore benefit when we find solace in nature. The main problem I have with this theory is that it doesn’t explain my former neighbour who thought nature was untidy, a woman I met on a walk who told her child not to pick the bilberries as they’re dirty, the loss of Northumberland’s Sycamore Gap tree, nor the council which chopped down mature cherries to make way for a city park. Only a few examples, but I know that you have had similar experiences as you shared your own sad tree felling tales.

Whether innate or not, this growing body of evidence clearly demonstrates that spending time with nature is good for your health even for those who don’t have the tree gene.

The healthy effects of green spaces are often attributed to what they lack. Pollutants, including light and noise, which are contributory factors in stress and stress-related illness, are absent from forests. Time spent there gives your system a boost because it gets a break from chronic stress and short-term stressors can actually strengthen immune system function. However, this doesn’t explain why when in an urban environment with all those same pollutants, health benefits have been observed when research participants only have a window with a view of a green space.

Another suggestion is what we do when we spend time with nature. A trip to the forest is likely to be a social or family outing, which may involve physical activity, sometimes strenuous. Both social connection and exercise are linked to better health. However, this doesn’t account for nature’s ability to stave off cognitive decline.

Perhaps then, it is awe? I never had the opportunity to experience the magnificent redwoods of California, but discovered a small redwood forest in the north of Spain. It wasn’t as old as other redwood forests, but I felt immense awe looking up into its cathedral-like canopy. There were other visitors, but all maintained a quiet presence, as if in awe too.

Awe is a state which arises when you encounter a phenomenon that blows your mind, such that your current knowledge doesn’t account for what you’re experiencing. Time spent reflecting in the forest can create peak experiences in which awe is present, enabling a reframing of a negative experience or mood. The experience temporarily suspends the stress response in the same way social connection and exercise does. Awe is a new area of study, so its impact for health, mental well-being and cognitive function is yet to be verified, leaving it open as to whether awe is the reason behind the effects of green spaces on human health.

The answer, however, could lie within nature itself - trees (and plants) directly affect human physiology.

Altruistic Trees

It begins with trees’ ability to remove pollutants from the air. This handy tool, displays the pollutants a specific tree near you removes from the air (and also the extent to which it manages stormwater). It works best if your tree is in the US.

I applied the app to the largest oak in our garden. The feedback is revealing. On average 20 lbs (9kg) of carbon dioxide is released into the atmosphere for every gallon (4.5l) of fuel used in cars. Compare that to my one oak which soaked up around 16,000 lbs (7300 kg) in its first 20 years. We need a lot of trees and the older they are, the better.

In addition to extracting pollutants and feeding them to soil between their roots as healthy nutrients, tree leaves also collect particles which filter the air. The end result is being able to breathe more easily. The cleaner air and water provided by trees are beneficial factors in health improvement.

Yoga in the Woods

The health benefits of simply sitting mindfully with the forest are so positive that Japan’s government invested in a forest bathing health programme.

The deeper the [forest bath] walk goes, I just feel like I am both guided into nature and I am guided into the depth of myself. ... There’s no rightness there’s no wrongness, there’s just being.

Tam Willey, certified forest therapy guide and founder of Toadstool Walks.

The practice, which entails engaging all the senses while spending time in the forest, arose out of a health crisis in Japan related to the stress-related illnesses arising from increased time spent with technology. Designated forest trails were equipped with medical professionals who not only assess individuals walking the path and provide health advice, but over the course of thirty years have contributed to a vast body of knowledge on the effects of forest bathing on human physiology.

Have you ever noticed a blue, smokey haze over a conifer forest, especially after rain? If you have, then you have witnessed the by-product of the trees’ transpiration.

In last week’s post, I shared how plants release a chemical mix which is communicated to other plants in the area, generally warning them of danger. Some plants, but in particular conifers, release terpenes into the atmosphere. They combine with moisture and ozone molecules to form tiny particles which scatter blue light. Hence the blue hazy effect you may have witnessed. It is believed to be a conifer forest’s temperature regulation system.

Terpenes also affect humans and in a positive way. Exposure to terpenes reduces physiological stress responses, blood pressure, heart rate and inflammation.

If you have stiff joints, time spent with conifers might help alleviate your symptoms.

Green Pill Dosage

If the forest is a pill, then what dosage would be good to take?

Several researchers have addressed this question and results are promising. You don’t need to become a hermit and cast yourself off into the wilds to feel the benefits. In the UK, one study found that just two hours a week in nature is associated with self-reported well-being and good health across all social groups. It didn’t matter if you did it all in one go, or over a period of short visits, and if you were feeling lazy, that didn’t matter either.

The findings of this study (and other replications) led a team to develop a phone app, NatureDose, to help people ensure they get their 120 minutes per week in nature. They also developed NatureScore which tells you how nature rich your area is, and where you might be able to go to get a higher nature score. The team plans to keep the apps free, but hopes for funding to track time spent in nature over longer periods of time and to compare it with long-term health. It is one means for precisely identifying what it is about elements of the natural world (like terpene rich environments) that yields the results I’ve described above.

Meanwhile, I’m getting back to my daily dose of the green pill. I know it works in the same way as I know the water potion works.

Embers

I used to be a fan of the bookstagram world, and was pleased to discover

Simon Haisell

has brought his own bookstagram to Substack. It goes by the same name as it does in Instagram,

Footnotes and Tangents

, and beginning January 1st, 2024, he plans to host a chapter a day read of War and Peace alongside the a slow read of Wolf Hall by Hilary Mantel. I intend to join both, so hope to bump into you over there at his own fireside gatherings.

Come meet the slow readers

Shortly after launching The Fiertzeside I mentioned permaculturalist, Heather Jo Flores. She particularly encourages women (but not exclusively) to become involved in permaculture practice. She has a new 40 day writing challenge for Wild Women (and I’m sure for wild men too), which I began yesterday. Let me know if you decide to take up the challenge too!

For anyone new to The Fiertzeside, please check out the Community Area, particularly the Introductions, where you’ll learn a little more about others’ work and interests. I have been updating this as we’ve been going along, but have decided to do this more systematically by setting time at the end of each series to update the community area. I’ll let you know in the embers when the community area has been added to. Please be patient with me if your name and/or newsletter don’t appear immediately.

Up Next

Like access to good health care, access to green space is linked to social inequity. Next week, we’ll take a trip to Mexico City (and elsewhere) to see how this issue is being addressed.

Beyond The Fiertzeside

Below are the sources used in the writing of this post for anyone who wishes to dig deeper.

On radio

Trees: Our Mental, Physical, Climate Change Antidote (Listen to or read this article which describes several research studies into trees and health and discusses the social implications)

Absorbing Nature and Finding Inner Peace Through ‘Forest Bathing’ At The Arnold Arboretum (personal subjective experience)

Articles in the media and university sites

The Health Benefits of Trees (a short outline of one person’s research at Harvard’s School of Public Health)

Research that takes your breath away: The impact of awe (article on Michelle Shiota’s work into awe)

Forest Bathing for Health: How Nature Nurtures Wellbeing (an overview of the benefits of forest bathing)

The Blue Haze of the Great Smoky Mountains (the terpene phenomenon)

Nature Is Medicine. But What’s the Right Dose? (article on NatureQuant’s apps)

‘Forest Bathing’ Is Great for Your Health. Here’s How to Do It (article by forest bathing expert, Dr Qing Li)

Scientific reports

Urban Trees and Human Health: A Scoping Review (The full literature review)

Spending at least 120 minutes a week in nature is associated with good health and wellbeing (full report)

The association between neighborhood greenness and incidence of lethal prostate cancer: A prospective cohort study (full report)

1. I am not saying you should stop following your doctor’s advice. As you’ll see, the story is more complex and there is a great deal more work to be done to gain full understanding of this phenomenon.