WHY YOUR SENSE OF SMELL MATTERS

How’s your sense of smell? In the recent – and ongoing – COVID crisis, our ability to smell (or not) has become one of the key indicators of whether we might have the virus. Indeed, the latest studies suggest that smell tests would be more effective than temperature tests in gaging who has and who hasn’t got COVID-19.

I lost my sense of smell back in April, when (like almost every Londoner I knew) I suspected I had the virus. Hour after hour I self-diagnosed on the NHS website, only to be told that I categorically didn’t have COVID. Daughter Number Three – who hopes to study medicine next year – stuck a branch of rosemary under my nose and, when I couldn’t smell a thing, shooed me back to bed.

Scientists have now worked out why so many (75% of those testing positive) lose their sense of smell with COVID.  Apparently it’s not the olfactory neurons (smell cells) that are invaded and destroyed but a support system of cells. This is why we typically regain our sense of smell within a week.  Scientists haven’t yet worked out why some people lose their ability to smell for much longer.

Unable to smell anything (a condition known as anosmia), I began to obsess about what it is to smell. I’ve always been a bit preoccupied with smells (one reader of my novels once asked why every location had a smell), but losing the ability to decipher odours took my preoccupation to a new level.  Smell is our constant, unacknowledged companion, an underrated miracle, the Cinderella of the five senses (until now, that is). It’s the only sense that goes direct to the emotional and memory centres of the brain. All other senses pass through a brain-part called the thalamus – a sort of processing switchboard which orders and files our experiences. Which might explain why certain smells can trigger such powerful and evocative memories.

Recently scientists have found smell receptors in other body-parts, from skin and blood to intestines and lungs, leading to speculation that our smell receptors could be responsible for much more than detecting odours, like triggering the release of chemical messengers to ensure we create new cells or neurons (for instance).

We know that our sense of smell can fade as we age (many dementia sufferers lose their sense of smell and taste altogether, and loss of smell is often a sign of early cognitive decline, particularly in diabetics) putting us at risk of all sorts of things – smell is our early detection system for a range of dangers, from smelling fire or a gas leak to identifying rotten food.

But smell is also a source of profound pleasure, from the garlic-herb laden smell of cooking to the smell of damp forest to the smell of flowers. When we lose our sense of smell we lose a little bit of ourselves, and reading written accounts of people learning to live without any smell at all is sobering, sometimes heart-breaking.  Here at the Age-Well Project we’re not just about surviving. In fact we’re more interested in thriving – enjoying full and curious lives for as long as we can.  That means being able to smell the food we’re cooking, the plants we’re growing and the air we’re breathing.

A study out last week rather startled me. Researchers found that mice fed a moderately fatty, high-sugar diet (a mouse version of the Standard American Diet apparently) showed a more rapid decline in their ability to learn and remember smells. The researchers believe excessive sugar may be the culprit, somehow causing the olfactory sense to deteriorate.

In a normally healthy person, smell cells are remarkably resilient, as plastic as brain cells. They renew themselves every four to six weeks.  Some experts describe our sense of smell as another muscle – use it or lose it. This becomes more important as we age. Because by the time we reach 75, 80% of us will have an impaired sense of smell.

But we don’t have to lose our ability to smell… It appears that we need the stimulation of smell, not only to improve our smell cells but to preserve them in the first place: studies show that rats confined to an odour-free environment lose their ability to smell, only regaining it when they return to an environment rich in odours.

In other words, start sniffing and smelling. I was lucky enough to smell-walk with odour expert, Dr Kate McLean, a week before lockdown. Together we sniffed our way around a south-of-England town, with Kate explaining why our ability to keep smelling is so important. She also explained why tulips no longer smell.  The scent has been bred out of them because supermarkets want long shelf life and we – the purchasers – prefer blowsy good looks to perfume.  So if we lose our sense of smell it’s (partly) our own fault! And another reason to grow our own (perfumed) flowers, perhaps.

We can still work our smell-muscle in the kitchen.  I’ve been repeat-cooking one of my favourite recipes on this site, Italian bean stew, just to flood the house with its pungent, earthy aroma.

If you’ve lost your sense of smell, or not managed to regain it post-COVID, you can do an organised programme of smell-training here .

To learn more about Dr McLean’s smell-walks and works, visit her site here.

I’ll be writing about the therapeutic power of certain scents and smells in a future post. In the meantime, lockdown is a perfect opportunity to practise your smelling!

Annabel