A few years ago my teenage daughter was complaining that our local charity shops ‘smell like old people’, Leslie Kenny tells Good Health.
The entrepreneur, who co- founded the Oxford Longevity Project – a non-profit organisation that works in collaboration with Oxford University to educate people about healthy lifespans – has since become a vocal advocate on an issue that feels strictly taboo.
‘Whenever I raise this subject people say, ‘Yes, I know exactly what you mean. I know that smell’,’ she says.
‘It is a universally recognised phenomenon that we don’t talk about at all – unlike the way we can talk about normal body odour.’
But is ‘old people smell’ a problem other than being undesirable – could it be a signal of underlying health issues?
Intriguingly, the idea is increasingly being investigated by researchers – with some evidence that blocking it might also help to keep skin healthier and younger-looking, and that dietary changes, particularly eating mushrooms, may help to banish it.
It is already scientifically accepted that our body odours give out vital clues about our health.
For instance, acetone breath is linked to a worrying complication of uncontrolled diabetes.
In Japan, where nearly a third of people are aged 65 or older, they have a word for the ‘old people smell’ – kareishuu
Some researchers believe eating mushrooms may help combat the ‘old people smell’
But ‘old people smell’, which may start as early as mid-life, is less well known – although in Japan, where nearly a third of people are aged 65 or older, they have a word for it, kareishuu.
For a quarter of a century Japanese scientists have been studying the phenomenon. The foundations for this were laid in 2001 by a study published in the Journal of Investigative Dermatology, where researchers analysed the sweat from 22 healthy volunteers of various ages.
They reported that when people passed the age of 40 they increasingly emitted a chemical called 2-nonenal.
The investigators described it as ‘an unpleasant greasy and grassy odour’. (Other researchers have said that it smells like mothballs coupled with basement air, out-of-date canned food and even pungent cucumbers.)
The scientists, who were working for the Japanese commercial cosmetics giant Shiseido, suggested that 2-nonenal is formed when the fats in our skin are broken down by oxidative stress – damage caused by free radicals, which are molecules linked to environmental factors and bodily processes, and that harm our cells and tissues.
Oxidative stress can increase as we get older, because our bodies’ levels of protective antioxidants – such as vitamins C and E, and glutathione – fall.
Another study by scientists at Shiseido, published in 2021 in Biochemical and Biophysical Research Communications, suggested the build-up of 2-nonenal may age our skin as well as making us smell.
This was based on lab tests on skin cells which showed that 2-nonenal prompts keratinocytes, cells in our skin’s outer layer, to kill themselves. This makes the skin look thin and reduces its ability to heal.
Other independent studies support the idea that odours change as bodies age, with age-related alterations found in several animals, including rabbits and monkeys.
In July, researchers in South Korea confirmed that old-aged mice also give off signature old-rodent odours that their fellows can detect, reported the journal Scientific Reports.
Humans, too, can smell ageing on each other, according to a 2012 study in the journal Plos One, led by Johan Lundstrom, then a researcher at the Monell Chemical Senses Centre in Philadelphia.
Professor Lundstrom, now a professor of psychology at the Karolinska Institute in Sweden, was inspired to conduct the research because he often visited senior citizens’ homes and noted they shared an odour – the same as in the old people’s home his mother ran in Sweden.
He wondered if it was characteristic of the elderly themselves. He tested this by collecting older people’s odours, in the form of sweat samples from the underarms of people aged from 20 to 95, and had them blind-tested by volunteers.
As he reported at the time: ‘Participants were able to correctly assign age labels to body odours originating from old-aged donors (75 and above), but not to body odours originating from other age groups.’
It seems that the chemical 2-nonenal is very smelly indeed.
The human nose can detect it at only 100 parts per trillion, compared with 500 parts per billion (or 5,000-fold higher concentrations) for pine and lemon scents, according to a 2002 study by the University of California at Berkeley. The researchers described the smell of 2-nonenal as ‘pungent cucumbers’.
The smell is also familiar to Dr Justine Hextall, a consultant dermatologist at University Hospitals Sussex NHS Trust and Tarrant Street Clinic in Arundel, West Sussex.
‘It is something that I sometimes notice when examining older people,’ she told Good Health. ‘It can also be experienced in someone’s house, and particularly on their clothes, furniture and bedding.’
But not all of us will end up ‘smelling old’.
The original Shiseido study in 2001 found that half of the volunteers aged over 60 produced so little 2-nonenal that it could barely be detected.
For those affected, ridding themselves of the odour may be challenging.
Leslie Kenny warns: ‘One of the problems with trying to shower it off is that 2-nonenal gets stuck in our skin layers and ageing skin becomes slower at sloughing this off.
‘You can’t mask it with perfume,’ she adds. ‘The perfume simply layers on top of it, giving it a musty smell. What you want to do is get rid of it from the inside out.’
She explains: ‘The smell is caused by oxidation of molecules in sebum [the skin’s natural oil]. It’s young sebum that makes babies smell delicious. But in old age, sebum can oxidate and go rancid.
‘Studies show that if you don’t have enough antioxidants in your diet, then that smell builds up. What’s more, it can linger because our skin cells don’t replace themselves so quickly when we age.’
Leslie Kenny recommends eating more mushrooms as they are high in ergothioneine, a powerful antioxidant with anti-inflammatory properties that may stop sebum going off.
‘You can get ergothioneine from any mushrooms, but it is particularly high in Japanese shiitake mushrooms and oyster mushrooms.’
Ergothioneine is also found in both red and black beans.
‘Mushrooms are also a source of spermidine, a compound that activates autophagy – the regenerative process that prompts faster cell turnover, and thus gets rid of smelly 2-nonenal,’ says Leslie Kenny.
Eating aubergines may also help significantly, according to a study published in May in the journal Molecules. Aubergines are rich in polyphenols – plant compounds with powerful antioxidant properties.
Now pharmacists at Hanyang University in South Korea have found that, in lab studies, aubergine polyphenols are effective at removing 2-nonenal from ageing skin – and may also prevent it from forming there in the first place.
What’s more, it seems that aubergines may also stop 2-nonenal from damaging our keratinocyte skin cells and causing visible ageing.
Other research by Shiseido in 2017 suggested that supplements of co-enzyme Q10 can reduce levels of 2-nonenal emissions. Co-enzyme Q10 is a vitamin-like substance found in small amounts in meat and fish, thought to have antioxidant properties.
Persimmon fruit extract, meanwhile, is being touted commercially as an antioxidant that can penetrate human skin to neutralise 2-nonenal.
A company in Japan called Mirai Clinical sells a £16 persimmon soap bar that promises to eliminate the odour, which it describes as ‘a greasy, unpleasant smell often compared to old books or stale oil’.
Dr Hextall adds that, more simply, adopting some healthy lifestyle habits – including dietary changes – may bring the most bountiful benefits.
‘Certainly we should avoid anything that increases oxidative stress in our bodies, such as smoking, drinking and work or emotional stress,’ she says.
‘Eating a healthy diet rich in antioxidant foods [fruits, vegetables, wholegrains, nuts, seeds, herbs and spices, and even cocoa] may also help significantly.’
Live longer, smell better, how could that be wrong?