Tag: taste

Dec. 21, 2022 – In some relationships, women are the heart, the vision, and the brains. In our marriage, my wife is the nose.

“What happened to the milk that was in the fridge?” she’ll ask.

“I drank it.”

“Didn’t you notice it went bad?”

Or …   

“You were eating sardines again, weren’t you?” she’ll accuse.

“I had ’em for lunch 2 days ago!”

Or …

“There’s something dead in the house,” she’ll insist.

Sure enough, in the basement, behind the couch, is a tiny dead mouse.

“Women generally have a better sense of smell than men,” says Richard Doty, PhD, director of the Smell and Taste Center at the Hospital of the University of Pennsylvania. “And the disparity between the genders gets greater with age.”

The reason is not well understood, but it appears to be a cradle-to-grave advantage. “If you put breast pads [from nursing mothers] in a bassinet and observe the rooting or orienting behavior of babies, the females will generally be more responsive,” he says. And when researchers in Brazil autopsied the brains of men and women over 55 with jobs that could optimize their sense of smell (restaurant kitchens, for example), they found the women had 43% more cells in their olfactory bulbs on average than the men.

But smell remains crucial to our well-being. We’re learning more and more that our sense of smell is closely linked to our health – and could one day be used for monitoring our health and predicting disease.

What Happens When You Smell Something

Consider what happens when we detect an odor – something we do thousands of times a day. For something to have a smell, it must give off molecules. We inhale these molecules into the tops of our noses, where 6 million to 10 million specialized receptor cells await. Some molecules contain multiple chemicals, so they bind to families of receptors, creating a scent pattern. 

Once this happens, the receptor cells message the olfactory bulb at the base of the brain, and the process of recognition and reaction begins. Sometimes, that happens right away (rotting flesh). Other times, it takes a bit. (“Hmm, what notes are you finding in the chardonnay?”) And sometimes, nothing registers at all. (When you have a cold, mucus prevents the molecules from fighting through.)

“Most things we think of as taste depend upon the smell system,” he says. “That’s why a significant number of people who come into our clinic complaining of being unable to taste anything actually have a smell problem.”

The same receptors found in the nose have also turned up in the kidneys, heart, and lungs. Why that’s so isn’t clear, but Mainland believes it’s because these cells have multiple functions. For example, some appear in the “carotid body,” a small cluster of cells near the carotid artery in the neck, and “seem to be able to sense how much oxygen and carbon dioxide is present – basically measuring and responding to lactate as if it were an odor.”

Smells can also trigger memories, such as a sniff of a perfume that makes you think of the person who wore it, or the aroma of food cooking that reminds you of your grandmother. These “olfactory flashbacks” happen because the brain’s smell-processing center links to its emotion and memory hub. A study from Wheeling Jesuit University in West Virginia found that the smell of cinnamon improved brain function and working memory, a finding that could help us treat dementia. 

“Smell dysfunction can be a very early indicator of these things,” says Doty, so if you notice anything amiss, it can’t hurt to consult a doctor or arrange to be tested for olfactory problems. You can use the SCENTinel rapid smell test mentioned earlier or the gold-standard University of Pennsylvania/Sensonics’ Smell Identification Test (around $30). Both are self-administered and involve scratching and sniffing cards with various scents. The results provide a baseline for your sense of smell and may also indicate disease. For example, “about 90% of people who develop Parkinson’s had demonstrable smell loss early on,” Doty says.

It may even be possible to smell disease. My wife, “the nose,” is a registered nurse at our local hospital. Many years ago, when she was pregnant, she walked into a patient’s room and had to turn around right away. “There was an overwhelming smell of decomposition,” she recalls, “like if you were hiking and came upon a dead animal.”

You May Not Be Sick – Just Aging

Like hearing and vision, our sense of smell gradually weakens over time. Doty’s research shows that 75% of people over 80 have “some demonstrable deficit.” Between ages 65 and 80, this is true for half the population. And among those over 65, 5% to 15% have no sense of smell at all (a condition called anosmia).

This decline is believed to be caused, at least in part, by the colds we catch over the years. “The olfactory endothelium, or membrane at the top of the nose, accumulates little islands of damage called metaplasia every time we have a bad cold,” explains Doty. “So, by the time we’re in our 60s and 70s, something that otherwise would be innocuous, like the common cold, can take us over the waterfall.”

A big area of research right now is whether age-related smell loss can be slowed or stopped, and if our sense of smell can be improved. Not really: Receptor cells can’t be strengthened by working them out, so to speak. And once they’re damaged by viruses, accident, or aging, they can’t be regenerated. 

“We found that most often, the variants that predicted lower intensity [for smells] were the newer variants,” she says. “And in olfaction, our genes are mutating faster than in other families of genes,” Mainland says. 

If anything is happening, it will take centuries to unfold. And any ability to smell that we have lost may have been replaced or compensated for by our gaining new ones. (Like smelling a gas leak, something prehistoric man had no need to recognize or fear.) Like every other part of us, our sense of smell is always evolving.

Even more intriguing discoveries lie ahead. Mainland points out that the mapping from chemical structure to olfactory perception is unknown (unlike in vision, where wavelength translates into color, and in hearing, where frequency predicts pitch). 

“There is not a scientist or perfumer in the world who can view a novel molecular structure and predict how it will smell,” he says. His research goal is to develop that.

Indeed, a recent global survey by the Ericsson ConsumerLab found that most consumers expect to be able to smell movies and even products digitally through an “Internet of Senses” by 2030. 

Imagine that. If my wife is at work, I could text her a sample scent of the milk to see if it’s safe to drink.