Sniffing out good health

WHETHER it’s newly mown grass, freshly brewed coffee or the lavender scent a much-loved grandmother used to wear, there are aromas that instantly transport us to another time and place.

Compared to other senses, such as sight or hearing, our sense of smell is the one we think about the least.Yet our ability to smell – and what odours we can identify – has a big impact on our health and wellbeing.

The importance of smell has been pushed into the spotlight by Covid-19.As the coronavirus began to spread, doctors were puzzled that so many patients were saying they had lost their sense of smell. Similar stories were shared on social media.

By March ear, nose and throat specialists were advising anosmia (the medical term for losing your sense of smell) should be added to the list of Covid-19 symptoms.

PROFESSOR Vincent Deary, an olfactory expert based at Northumbria University, says: “What is unique is that the smell loss occurs early in the infection and there is no nasal obstruction, so it could be a really important marker of Covid-19.”

This was brought home to him when his sister, a community nurse, mentioned that both she and her husband had lost their sense of smell. Professor Deary warned his sister it might mean they had Covid-19, so she and her husband played safe and self-isolated. A few days later, both developed a fever and cough and were diagnosed with the coronavirus.

As Professor Deary points out: “If it hadn’t been for that chance conversation, my sister would have continued to work and could have passed the infection on to so many vulnerable patients.”

The association between aromas and our physical and mental health can be explained by anatomy, says Professor Nancy Rawson, a cellular neurobiologist based at the Monell Chemical Senses Centre in Philadelphia. “Our sense of smell is directly connected to the parts of our brain associated with memory and emotion.

“Odours activate receptors in the olfactory bulb, a structure near the bridge of the nose, which is only two connections away from the hippocampus and the amygdala – the learning and memory parts of the brain.”

Bizarrely, scientists have recently discovered that these olfactory receptors – once thought to be only related to smell – are also found in almost every part of the body including the heart, lungs, gut, skin and sperm.And they are now known to influence a wide range of crucial functions including blood pressure, breathing, blood sugar levels and wound healing.

Our ability to recognise smells fades as we get older, in much the same way our sight and hearing deteriorate. But it can be an early sign of dementia and other neural disorders. A study involving 3,000 adults, aged 57 to 80, found that 80 per cent of those who could not identify at least two out of five distinct odours – peppermint, fish, orange, rose and leather – were diagnosed with dementia within five years. Lead researcher, Professor Jayant Pinto, from the University of Chicago, says: “Loss of the sense of smell is a strong signal that something has gone wrong and significant damage has been done to the brain. “A simple smell test could provide a quick and inexpensive way to identify those already at high risk.” There is an even stranger connection with Parkinson’s disease.The combined data from seven large studies showed the loss of smell almost quadruples the risk of developing it.

Scientists at the University of Manchester found that some people can also sniff out Parkinson’s before there is any hint of a problem.

The discovery came when Joy Milne, a former nurse, attended a patient support group and noticed the other Parkinson’s sufferers had the same distinctive smell her husband Les developed 12 years before his diagnosis.

Researchers confirmed Joy was right by having her sniff T-shirts worn by both healthy people and those with Parkinson’s. She identified every one of the shirts worn by the Parkinson’s patients and said one from the healthy group had the same smell. Eight months later, the wearer was diagnosed with Parkinson’s.

Diabetes can also be spotted through a sniff test. Sweet, slightly fruity smelling urine is a sign of poorly-controlled blood sugar levels. However scientists believe the pong many people notice after eating asparagus is a harmless quirk of genetics.

Dogs are even better disease detectives as they have smell receptors which are 10,000 times