SMELL, STRESS, POETRY AND THE BRAIN

It’s national walking month, apparently. For me, every month is a walking month but I’ll admit that May is a particularly enchanting time to walk in Britain – hawthorn blossom, bluebells, birdsong in abundance. And air drenched in perfume.  Making May the ideal month in which to walk more. And to walk differently.

We know the brain loves novelty (we wrote about it here, as well as in our original Age-Well book). And so the easiest thing to do is to venture out into new locations. A survey carried out during the pandemic found that those who walked in new and varied places felt happier,  less stressed and more optimistic than those who obeyed orders and walked round the same old park/field/room, day after day. And I’ll come back to the significance of this for ageing well (specifically for fending off Alzheimer’s) in a moment.

But novelty isn’t restricted to changing our location.  Which is a good thing, because we need to be able to stimulate our brain wherever we are.  Let’s start with smell…  our olfactory receptors hibernate in the colder months, perking up as the weather warms.  The warmer the air, the longer that scented molecules from trees and plants hang around.  So, in May, not only is our olfactory bulb (the cluster of smell cells at the top of our nostrils) more receptive, and not only are plants more likely to be in full perfumed bloom, but the warmer air also traps these molecules for longer. Spring air is the best because it’s also moist – and when air is moist it passes more easily through the mucus lining of our nose.

Unsurprising then that studies show our olfactory system works at its best in spring, even if we’re not aware of it.

Now, here’s the interesting bit. Loss of smell has been linked to neurodegenerative disease, with some researchers suggesting that smell tests should be routinely offered by doctors. A 2022 study found that loss of smell (known as anosmia) was an important early sign of Alzheimer’s-related cognitive impairment.

But there’s no need to panic, because studies also show that our olfactory system is much like a muscle – use it or lose it.  I’ve written about smell before but, for any of us wondering if our sense of smell is diminishing, the easiest thing to do is to take some smell walks – now, while our noses are most receptive and while nature’s scents are at their most intense.

And if you need any further convincing, just read this extraordinary hot-off-the-press study that found mice who regularly sniffed mint had improved cognition. How come? The researchers aren’t quite sure but they think a compound in menthol helps regulate inflammation by reducing a protein called interleukin-1-beta.  You can read the science yourself, but all you need to know is that six months of short exposures to menthol (via the nose) improved cognition in healthy mice as well as in cognitively impaired mice (actually, menthol appeared to stop Alzheimer’s in its tracks when used on mice with dementia). As the researchers wrote: ‘This suggests that odors and immune modulators may play an important role in the prevention and treatment of Alzheimer’s and other diseases [like Parkinson’s] related to the central nervous system… stimulation of the immune system through exposure to certain fragrances, such as menthol, can have a beneficial effect on cognition.’

Warm, post-rainfall, spring evenings are the very best time. As you walk, imagine you’re a dog and sniff constantly at the air. Even better, gently rub aromatic leaves between your fingers as you pass them (rosemary, lavender, lemon verbena, juniper berries, pine needles), putting your fingers immediately to your nose. Sniff at the soil, at mounds of cut grass, at tree bark, at blossom.  Plunge your nose into Mexican orange blossom, ceanothus, bay trees (all of which can be found in front gardens  and urban parks). Sniff out water mint, wild garlic, bluebells and violets (all blooming now in the British countryside).

Not in the UK? Don’t worry, there are even more aromatic plants in warmer climes. And many more evergreen trees in colder climes. Just identify your local scented (non-poisonous) plants and go find them.  The more you sniff, the better your olfactory capabilities.  And the better (perhaps) your cognition will be.

Unlike soundwaves, which go through multiple filters and iterations as they pass to the brain, smells travel directly to the hippocampus (which is why smells often trigger powerful memories). But smells also pass immediately to the amygdala – the brain’s fear and anxiety centre. No filtering. No time lapse. Which is why the smell of lavender or chamomile, for example, can feel instantly calming (and why less pleasant smells can provoke instant reactions.)

This calming effect of a smell walk is also important. Because a study out this week links Alzheimer’s to stress.  Earlier studies have already indicated that stress can drive progression of dementia, but this latest study (done on mice) found a possible mechanism.  In female mice, stress had a response that didn’t present in male mice, prompting researchers to ask if this explains why more women get dementia.

Here’s a snapshot of what the researchers found: stressed female mice produced more beta amyloid – the protein thought to clog up and inflame our brains, stopping them functioning as they should. Male mice, subjected to the same stresses, didn’t produce beta amyloid.  I’ll quote: ‘In female mice, beta-amyloid levels … rose by around 50% within the first 2 hours of stress, and stayed elevated. Only about 20% of male mice exhibited a small, delayed increase in beta-amyloid.’

How so? Well, it appears that males and females respond differently to the stress hormone known as corticotropin-releasing factor (CRF). At least, in mice. Female mice absorb this hormone into their cells, which ultimately leads to a rise in beta-amyloid in the brain. The nerve cells of male mice, however, don’t absorb CRF. Somehow, they shake it off. No one yet understands how or why this happens, or whether it happens in humans.  But as women suffer from both higher levels of stress and of Alzheimer’s, researchers are about to investigate.

Taking a smell walk combines novelty with movement and a sense of calm (seek out pleasant aromas obvs).  But there are also other novel and calming walks that can be taken at this time of the year.

Recently, I’ve been on a nightingale walk (novel, calming and life-affirming, and at night our noses also typically work better), a dawn chorus walk, and a poetry walk.  The nightingale and poetry walks were both new to me. And while you might not have access to nightingales, we all have access to poetry.

So why take a poetry walk? Jonathan Davidson, the strolling bard who generously organised the walk I attended, put it like this: ‘The country walk is oddly transformed when we pause in our rambling and speak a poem to the open air. On my poetry walks I’ve observed that those who read the poetry aloud – and those who hear the poems – are given a new understanding simply by placing our very best endeavours in language into the infinite complexity of nature. One honours the other.‘

On our walk, poems were read that reflected things around us, from trees to bees. Suddenly we saw the same old tree and bee through a new lens, jolting our brain into firing and rewiring. Good for the soul, of course.  But good for the brain too.

And good for easing stress. The rhythm of poetry has been found to calm us, much like the rhythm of walking or breathing. I loved this recent article on reading poetry for better sleep.  And when I searched the pubmed global database of medical research I discovered that poetry for healing is nothing new (although we all knew that, of course).  In the US, it’s called Poetic Medicine. As one recent report put it: Patients, physicians, and health care workers can benefit in terms of well-being by access to reading, reflecting on, and writing poetry.

So here’s my recommendation for May: find some walks that are new to you in some way; breathe deeply and smell the sap, blossom, bark, wild mint; read a poem or two as you go.  Perhaps write one of your own. Or check Jonathan’s site for poetry walks (and classes) near you.

If you have a favorite poem for walking with, please share in the Comment Box. I’ve been enjoying this poem by Mary Oliver, which is just as pertinent to spring as to summer, and reminds us that a ‘stroll through the fields’ is more worthwhile than most of the things we fill our days with.

Wishing you all the happiest of May walking (and smelling)!

Annabel

PS If you missed my recent piece in The Observer on ‘The Walking Cure’, you can find it here, or an earlier piece in The Guardian on the best ways to walk, here . If you prefer a podcast, there are plenty out there but my most recent is here.

There are two chapters on how to take a small walk in 52 Ways to Walk if you want to know more about the remarkable healing powers of our olfactory bulbs, particularly when combined with movement.