A few years ago, on a visit to the offices of the Department for Environment, Food and Rural Affairs (DEFRA), I paused to admire a wonderful flowering plant in a meeting room. But when I touched its leaves, I discovered it was made of polyester. Of all the places I might have expected to find fake plants, DEFRA – the centre-point of our nation’s efforts to conserve and enhance nature – was not one of them!
It made me wonder whether it matters if plants are real or not with regards to the health benefits they’re known to confer. Could viewing ‘fake’ versions be just as effective in reducing stress and improving our mood – or do we need the real thing?
I’ve spent a lifetime thinking about plants. Indeed, the Institute I founded at Oxford provides evidence for policymakers to protect the Earth’s incredible biodiversity. But even I was surprised to find evidence which so clearly showed the health benefits of real plants over fake.
An experiment, in 2015, neatly demonstrated that for all the sophistication of modern fake flowers, nothing comes close to the impact of real nature on our body and mind.
Researchers asked students to view, for three minutes, either a planter containing fresh yellow pansies or a container of polyester pansies, identical in colour, size and markings to the real things.
The participants’ pulse rates were measured and they also answered questions about their state of mind. Surprisingly significant differences emerged.
Just looking at the real flowers led to a significant reduction in stress levels, compared with viewing the fake pansies. The students also reported feeling more relaxed when looking at the real pansies, it was reported in the International Journal of Environmental Research and Public Health.
We can all identify with this. Because there’s something special about touching, smelling, hearing, revelling in nature in all its glory.
When I worked at Kew Gardens, I was struck by how many visitors there didn’t just look at the blowsy borders or striking palms, but also stopped to inhale their fragrances, gently touching their leaves or stroking bark. (They ignored those stern signs telling them ‘Do Not Touch’ – I ignored them, too.)
Now I’ve discovered how our health really can be turbo-charged by interacting with nature.
As we will see, the key to living healthier lives can be as effortless as placing a spider plant on your desk, using lemon-scented soap or ensuring you always garden without gloves.
SMELLING ROSEMARY CAN BOOST BRAIN FUNCTION
Many health benefits are rightly attributed to the Mediterranean diet. But the positive impact of smelling the native Mediterranean herb rosemary is less well known.
Rosemary’s distinctive smell is due to an aromatic compound called 1-8-cineole, along with pinene and camphor. It helps to keep us awake and alert, aiding our productivity.
Although the precise biological mechanism is still under investigation, research published in 2022 in the journal Frontiers of Neuroscience suggests that we may derive mental benefits from smelling rosemary because of the way its aromatic compounds affect certain biochemical pathways in our blood.
Experiments have shown that raised levels of 1-8-cineole compounds can inhibit the action of two enzymes that normally break down neurotransmitters (chemical messengers) in the brain responsible for alertness and arousal. The effect of this is to prolong the life of these neurotransmitters, meaning we stay awake and alert for longer.
Fascinatingly, these enzymes are also implicated in conditions such as dementia, according to a 2022 review in the journal Frontiers of Neuroscience. These days I always have rosemary oil diffusing in my study at home, and it was very useful in my teenage son’s bedroom when he was revising for his exams – it helped to keep him awake!
HEALING POWER OF A VIEW FROM HOSPITAL BED
If you’ve been in hospital, I bet the view from your bed was not inspiring. And yet there’s long been good scientific evidence that this can make a big difference.
As long ago as 1984, US researchers found that patients in a suburban Pennsylvania hospital recovering from gallbladder surgery who could see trees from their windows recovered faster than those who looked out on brick walls. They also had better post-operative mental well-being and required less pain relief.
Why might this be? One theory is that our bodies have a biological preference to viewing nature and that this in turn produces a more positive emotional state.
This means that viewing natural scenes automatically triggers a physiological response, which in turn helps us to recover better from stress. In contrast, it’s thought, urban environments do not have the same effect, the opposite in fact, and can hamper recuperation, especially after stressful events.
Since then many subsequent studies have also found that a view of nature – even from indoors – can lower blood pressure, pulse and other physiological stress indicators.
SMELLING LEMON SCENT COULD HELP BREATHING
Gut-friendly food and drinks such as sauerkraut, kefir and yoghurt have never been so popular because of the way they boost the health of our gut microbiome, the collection of micro-organisms that research increasingly shows plays a vital role in our immune system, as well as our digestion.
But there’s also evidence that interacting with microbes in nature – like those in plants and soil – could enhance our gut microbiomes.
It’s little known that the microbiomes of plants and soil share similar bacterial communities to our own, composed of five major types (called Firmicutes, Bacteroidetes, Actinobacteria, Proteobacteria and Verrucomicrobia) that are also found in the human gut and skin.
When we spend time in nature, new evidence suggests the microbiome in plants and soil passes onto our skin and into our gut.
A recent study in Finland asked adults to rub their hands with a soil and plant-based composition three times a day for a fortnight. After two weeks they showed a significant increase in microbial diversity on their skin and in their guts much closer to that found in the soil. In addition, their blood plasma (the part of your blood that carries platelets, red blood cells, and infection-fighting white blood cells) had raised levels of a protein, ‘cytokine’, that helps control your immune system. The specific cytokine here, TGF-beta, is known for its ability to inhibit cell proliferation in the early stages of tumours.
It does seem as if the benefits of gardening without gloves could be enormous – as long as the soil hasn’t been treated with pesticides, of course, and you don’t have open cuts.
This rapidly emerging field of research raises the tantalising question of whether interacting with nature could potentially provide a treatment for people who already have auto-immune diseases, such as rheumatoid arthritis, and other serious disorders such as obesity and type 2 diabetes, Alzheimer’s , Parkinson’s, autism, depression and hypertension.
Interestingly, the Finnish study, published in the journal Future Microbiology, found that although there were still differences in microbes of the participants after 14 days, by 35 days they had disappeared.
This suggests that we need to keep ‘topping up’ environmental microbes – or our own not-so-healthy microbes will re-establish themselves
The zingy clean smell of lemon is often used in shower gels and hand soaps. Now there’s preliminary evidence that a lemon scent could be beneficial for people with respiratory conditions. A lemon’s distinctive smell comes from a VOC (a volatile organic compound, otherwise known as a smell to you and me), called d-limonene.
Studies show that as well as reducing stress, smelling d-limonene can reduce the effect of inflammation in the lungs, at least in mouse models on which this has been trialled.
This type of inflammation is characteristic of asthma, bronchitis and other lung conditions. The potential use of lemon peel scent to ease symptoms of asthma and other illnesses, is therefore of great interest.
Preliminary studies have also suggested that d-limonene could be conveniently given as an inhalation since it’s easily absorbed and used by the body and therefore can potentially provide direct and rapid reduction of inflammation in the respiratory tract.
CALMING POWER OF A WALK IN CYPRESS FOREST
A woodland walk can instantly make you feel better. The sight of majestic trees, the dappled light and the smells of nature all combine to trigger numerous physiological responses that calm us.
Indeed, such walks, known as forest bathing, have been prescribed by the health service in Japan as a medical intervention for almost 40 years – and Japan has more than 60 accredited woodland nature-therapy trails, many of which are studded with cypress trees.
Cypress trees release a woody, peppery scent, composed predominantly of the molecules ß-cadinene and cedrol, along with concentrations of the compounds alpha-pinene, ß-pinene and limonene.
Inhaling these scents triggers involuntary neural responses, resulting in significant reductions in heart rate and stress hormones in saliva.
These compounds can also apparently increase levels of lymphocytes in our blood. Lymphocytes are immune cells that seek out and kill malignant cells, including those causing tumours and cells infected with viruses, by producing proteins such as perforin and granzyme.
These proteins then kill the tumour/virus-infected cells by triggering apoptosis, a natural process leading to cell death.
In a 2018 study at the National Taiwan University, 25 people who went on a five-day trip to a forest with many cypress trees all had a significant increase in natural lymphocyte killer cells. And these elevated levels lasted for more than seven days after the trip ended.
If you don’t live near a cypress forest, simply diffusing cypress oil at home will probably produce similar benefits.
SPIDER PLANTS FOR CLEANER AIR
Considered one of the easiest house plants to grow, the spider plant also has health benefits.
One study, published in the journal Frontiers of Microbiology in 2015, found that placing a single spider plant in a room led to a significant improvements in both the number and diversity of beneficial plant bacteria. And another study found that spider plants had a positive impact on indoor air quality, efficiently reducing levels of pollutants including formaldehyde, toluene and ethylbenzene.
Never before has the spider plant on my desk been so cherished; it is not only improving the air quality but also the good bacteria in the air in my room, which has then been shown to transfer onto my skin and very probably into my gut.
In effect, I benefit from a ‘probiotic’ dose similar to those from drinking probiotic drinks – but delivered in the air, and all thanks to a plant on my desk.
HEARING BIRDSONG FOR POST-OP PAIN
Any surgery is stressful and probably none more so than remaining ‘awake’ under local anaesthetic.
Despite being clinically less risky, many studies show the stress is considerable and can last for some time after the operation, even prolonging recovery rates.
But there’s a natural remedy here: tuneful birdsong.
This has been demonstrated in several studies, including a fascinating one at a teaching hospital in Iran in 2019. Scientists examined the influence of natural sound on post-operative pain management in 57 women who had undergone elective caesareans. The experiment took place eight hours after surgery, when post-op pain is thought to peak.
The women were divided into three groups: one wore headphones with no sound; a second group had headphones with sounds of nature, including birdsong; and the third had nothing.
Clear results emerged. The women who listened to birdsong had significantly less severe pain than the other groups.
Sounds of nature can seemingly trigger pathways in our bodies that lead to reduced pain.
A bigger study, published in the journal Proceedings of the National Academy of Sciences in 2021, analysed data from multiple experiments involving participants from 11 different countries.
A staggering result emerged: listening to nature sounds resulted in an improvement of 184 per cent in clinical measurements including levels of pain, heart rate variability, blood pressure, anxiety and depression, compared to those who heard urban sounds or no sound at all.
Listening to birdsong produced the biggest reductions in blood pressure, pain and heart rate, while water sounds led to the best improvements in mood and cognitive performance.
But which birds help most? A 2016 study, published in the Journal of Environmental Psychology, found the best stress-relieving birdsong included blackbirds, dunnocks, blue tits, green finches and robins – those with acoustic signatures that were tuneful but complex, with repeated patterns and of comparatively low volume.
In contrast, less tuneful, repetitive jays, herring gulls, silver gulls and kites had the least benefit.
Other studies have also indicated that the squawks of crows and parrots are also less beneficial and in some cases can raise stress levels when we hear them.
WOOD PANELLING is NOT JUST FOR SHOW
There’s clear evidence that wood-lined rooms make us feel calmer, reduce eye fatigue and improve our cognitive performances compared to rooms decorated with other materials.
This may be something to do with the smell of the wood along with other visual details, such as how knotty the wood is.
Some trees, like conifers and softwoods such as pine trees, have resin ducts – hollow, tube-like structures from which the scent or VOC is emitted – in their trunks. (Hardwoods such as oak, sweet-chestnut and beech do not have these ducts.)
Even though scent levels released may be too low for us to notice consciously, they will be present in low concentrations in the air for a number of years after construction.
A 2014 study in Japan compared participants working in a room lined with cedar timber to others working in a room with no wood cladding. Clear differences in the air were detected before the experiment, with high levels of VOCs in the cedar room.
In both rooms, participants took a series of 30-minute maths tests specifically designed to induce anxiety. They sat behind a screen so that they couldn’t see the material lining the walls of the rooms. Fascinating results emerged.
Those in the unlined room showed a clear spike in their stress levels (measured by their amylase, an enzyme in saliva that rises when you are stressed) when taking the test. Those in the cedar-lined room showed no increase in stress at all.
But what about just looking at wood? Some studies indicate that, as well as its smell, the visible qualities of certain woods – the microscopic unevenness of its surface and knottiness – can also have positive health benefits.
Seemingly, this unevenness doesn’t only affect how wood appears but also deflects light waves as they hit the surface.
As a result, wood panels reflect only a tiny fraction of ultra-violet rays from UV lights and flickering computer screens, compared to those from surfaces made of polished and smooth manufactured materials, according to a 2019 study in the journal Wood Material Science & Engineering.
Researchers now believe that wood wall linings that reduce glare from computers and overhead strip lights can play an important role in stress relief and eye fatigue reduction.
ROSES COULD CALM ROAD RAGE
It’s said no flower smells as sweet… and now scientists have also shown roses can even make road rage disappear.
Researchers at the University of Sussex examined the effect of different smells on driving behaviour and found that inhaling rose scent resulted in the lowest average driving speeds, no crashes and drivers reportedly feeling happier and calmer behind the wheel.
The participants were evaluated in a simulated driving environment, and their performance in speeding and lane movements was assessed while being challenged with a series of anger-inducing road events, like other cars cutting across their path.
Other smells assessed included peppermint — which also had a beneficial effect — and civet (the musky odour used in perfumes obtained from the anal glands of exotic cats) which produced the worst results with many simulated crashes and angry driving tactics.
The clear take-home message from this study is that we should all have rose and peppermint scent diffusers in our cars – and never car share with a civet!
They’re the Christmas plant of choice for many – but researchers have found that the red leafed festive poinsettia, can also increase dark thoughts and tension.
A 2017 study in the journal Indoor and Built Environment found redleafed houseplants had a negative mental effect.
Participants viewed red-leafed plants while wearing a headset to monitor their brain activity in areas of the brain corresponding with feeling, judgment, vision, senses and emotions.
In comparison, two-toned green and yellow houseplants, such as some varieties of ivy, had strongly positive outcomes, including enhanced neural activity in brain areas associated with a more relaxed and calm state.
- Kathy Willis is a professor of biodiversity at the University of Oxford, a Cross Bench Peer in the House of Lords, and previously the Director of Science at the Royal Botanic Gardens in Kew.
- Good Nature by Kathy Willis (Bloomsbury Publishing, £20) is out on August 29. © Kathy Willis 2024. To order a copy for £18 (offer valid to 06/09/24; UK P&P free on orders over £25) go to mailshop.co.uk/books or call 020 3176 2937.
