Contrary to previously held scientific belief, the declining sense of smell in older people is not uniform, and their liking of many smells remains the same. Researchers at the University of Copenhagen reached this conclusion after examining a large group of older Danes’ and their intensity perception of common food odours.
The decline in smell has been demonstrated scientifically. Sense of smell gradually begins to decline from about the age of 55, and 75% of those over 80 show major olfactory impairment. While it was previously believed that one’s sense of smell broadly declined with increasing age, a study from the University of Copenhagen reports that certain food odours are significantly more affected than others.
Eva Honnens de Lichtenberg Broge and her fellow researchers tested the ability of older Danes to perceive everyday food odours. The researchers measured how intensely older adults perceived different food odours — as well as how much they liked the odours.
“Our study shows that the declining sense of smell among older adults is more complex than once believed. While their ability to smell fried meat, onions and mushrooms is markedly weaker, they smell orange, raspberry and vanilla just as well as younger adults. Thus, a declining sense of smell in older adults seems rather odor specific. What is really interesting is that how much you like an odour is not necessarily dependent on theintensity perception,” observed Eva Honnens de Lichtenberg Broge.
For example, liking seemed to be largely unaffected for fried meat, onions and mushrooms, despite the largest decline in intensity perception was seen for these specific odors. The ability to smell coffee declined, among other things, though they didn’t like the aroma of coffee to the same degree as younger adults.
The test subjects included 251 Danes between the ages of 60 and 98 and a younger group consisting of 92 people between the ages of 20 and 39.
Everyday food odours
Instead of using odours of chemical origin, which is commonly the procedure when testing the sense of smell, Eva Honnens de Lichtenberg Broge developed a test kit including 14 natural food odours familiar from everyday life, including bacon, onions, toast, asparagus, coffee, cinnamon, orange and vanilla. The odours, mainly made from essential oils, were presented to participants by sniffing sticks.
The food odours were chosen based upon commonly consumed foods and dishes that older people often eat and enjoy most according to meal plans and surveys from a Danish catering company that provides food for the elderly.
What’s the story?
The researchers can only speculate as to why the declining sense of smell in older adults seems to be odours specific, especially for savoury food smells and why, in some cases, liking is largely unaffected.
“This may be due to the fact that these are common food odours in which saltiness or umami is a dominant taste element. It is widely recognised that salty is the basic taste most affected by aging. Since taste and smell are strongly associated when it comes to food, our perception of aroma may be disturbed if one’s taste perception of saltiness is impaired to begin with,” Eva Honnens de Lichtenberg Broge suggested.
Nutriton and quality of life
The researchers hope that their findings will help improve nutrition for the elderly. While the sense of smell is important for stimulating appetite and our serotonin levels as well, according to Eva Honnens de Lichtenberg Broge, their study demonstrates that the sensitivity of one’s sense of smell need not be decisive — participants’ liking of certain foods remained unchanged.
“Our results show that as long as a food odour is recognisable, its intensity will not determine whether or not you like it. So, if one wants to improve food experiences of older adults, it is more relevant to pay attention to what they enjoy eating than it is to wonder about which aromas seem weaker to them,” concluded Eva Honnens de Lichtenberg Broge.
Source: University of Copenhagen – Faculty of Science
Journal information: de Lichtenberg Broge, E.H., et al. (2021) Changes in perception and liking for everyday food odors among older adults. Food Quality and Preference. doi.org/10.1016/j.foodqual.2021.104254.
