Scent and Food Choice

Oh, but they smell so good (photo
from www.eatthis.com/unhealthiest-foods-2018/).

Welcome back. A few months ago, I almost reviewed a study of how scents (aromas) affect our choice of food. Now that most people are under stay-at-home orders, captive to scents and possibly snacking too much or on all the wrong things, it’s time for me to follow through.

The background for the study is that marketers, who usually rely on visual and auditory cues, are increasingly adopting ambient scent. This is occurring in a range of venues, and food-related scents are common, such as cotton candy, popcorn and caramel apples in theme parks, cinnamon sticks, rosemary or heated cilantro in restaurants, and chocolate and baked bread in supermarkets.

Researchers affiliated with South Florida and Louisiana State universities set out to determine if and how such ambient scents influence children’s and adults’ food choices. For added significance, they focused on the scents of indulgent (unhealthy) and nonindulgent (healthy) foods.

In the course of their study, the researchers conducted a series of tests--2 in a middle school cafeteria, 1 in a supermarket, 4 in the lab. The basis for their testing hypotheses is cross-modal sensory compensation, which they describe in some detail and I’ll summarize.

Olfactory and Gustatory Trade-Off
Neuroscience has identified brain regions where inputs from our sensory systems (visual, olfactory, auditory, gustatory and haptic) combine, interact and influence one other.

Reward values (subjective pleasantness) assigned to sensory system stimuli by the brain’s reward centers are dependent on a number of factors, such as prior experience. For gustatory (taste) stimuli, high-calorie, high-fat and high-sugar (indulgent) foods tend to have the highest reward values.

Although the reward centers discriminate among stimuli intensity, they do not distinguish among stimuli of different sensory systems. Because the olfactory (smell) and gustatory systems are strongly interconnected, foods do not have to be eaten to activate reward centers.

Going further, the researchers posit that sufficient exposure to ambient scents of indulgent, unhealthy foods can satisfy the brain’s reward mechanism, reduce the desire to consume indulgent foods and enhance the preference for healthy foods. In contrast, scents of healthy foods or the lack of an ambient scent will have no effect, because of their lower reward value.

The researchers point to studies that show prolonged exposure to a certain scent can induce satiation and reduce the desire for products with that scent.

Testing Cross-Modal Sensory Compensation
I’ll review 2 of the study’s 7 tests and wrap up with a third to illustrate what was done and the outcomes.

Middle school--Testing in the cafeteria of a middle school with about 900 students, the researchers used an ultrasonic scent nebulizer to produce ambient scents of pizza and apple on two separate days. A third day was the control, with no ambient scent. Students’ entry was deliberately slowed to longer than two minutes to prolong the ambient scent exposure.

Cafeteria items were coded as healthy or unhealthy before testing. Of the total number of items sold on each day (over 2,800), the lowest percentage of unhealthy items was sold on the day with the ambient scent of pizza, 21%, compared to 37% on both the apple scent and control days.

Middle-school student choice of healthy and unhealthy foods after being exposed for longer than two minutes to pizza, apple or no ambient scents (from journals.sagepub.com/doi/full/10.1177/0022243718820585).

Supermarket--Testing in a supermarket one Saturday afternoon, research assistants used a nebulizer to expose incoming shoppers to either chocolate chip cookie or strawberry scents, while offering them a $10 gift card if they would turn in their shopping receipt (minus credit card info) at the exit. The recruitment process ensured prolonged exposure.

Purchased products were coded as healthy, unhealthy or neutral/nonfood. Of the total number of items purchased, the percentage of unhealthy items was lower and of healthy items higher with the cookie ambient scent than with the strawberry ambient scent. The proportion of neutral/nonfood items was similar with both scents.

Supermarket shopper purchases of healthy, unhealthy and neutral/nonfood items after being exposed for longer than two minutes to cookie or strawberry ambient scents (from journals.sagepub.com/doi/full/10.1177/0022243718820585).

Wrap Up
All tests confirmed that prolonged exposure to the indulgent, unhealthy food scent sufficed to overcome the initial craving.

In one of the four lab tests, for example, participants exposed to the cookie scent for less than 30 seconds chose the unhealthy food twice as often as when they were exposed for longer than 2 minutes (45% vs 22%).

Bottom line: If you wait it out, there’s a good chance you’ll reach for the healthy stuff. Thanks for stopping by.

P.S.
Study of cross-modal compensation effects in Journal of Marketing Research: journals.sagepub.com/doi/full/10.1177/0022243718820585
Article on study on TIME magazine website: time.com/5506851/how-to-stop-eating-junk-food/

Fragrance Free

Welcome back. In a long-ago blog post, Time for Allergies, I wrote: I’m no longer beset by hay fever, yet perfumes and fragrances can do me in. The entire cosmetic line my wife favored when she and I first got together was in jeopardy until we determined that the non-fragrant, hypoallergenic, couldn’t-possibly-bother-you cosmetic base was the culprit. Being a mile downwind of that base was enough to shut down my breathing, clunk.

Am I the only one bothered by perfumes or products with added fragrances? No, of course not. In fact, a recent study of American adults characterized the prevalence and types of exposures, health effects and societal impacts of fragranced products. It’s the latest work on the topic by the investigator, who’s currently with the University of Melbourne in Australia.

Fragrance-free lotion.
No artificial fragrances.

Online Survey
Data for the study were collected via a comprehensive online survey of 1136 U.S. adults, representative of age, gender and region.

Survey questions included exposure to fragranced products from both one’s own use and others’ use, health effects, exposure in the workplace and awareness of product ingredients and labeling.

Fragranced products were categorized as air fresheners and deodorizers, personal care products (e.g., soaps, deodorant, shampoos), cleaning supplies, laundry products, household products (e.g., scented candles, toilet paper, baby products), fragrances (e.g., perfume, cologne, aftershave) as well as other.

Health effects surveyed ran the gamut from migraines to asthma attacks to neurological and musculoskeletal problems. 

“Fragrance” in the bottom line of a lotion’s ingredients label.
Hmmm, what’s in that fragrance?

Key Findings
As you’d probably guess, nearly everyone was exposed to fragranced products at least once a week, and it wasn’t always a pleasant whiff. Those exposures caused one or more adverse health effects in over a third of those surveyed and potentially disabled 17%.

Exposures in the workplace caused 15% of survey respondents to become sick or lose workdays or even a job. Surprisingly, little more than half of the respondents would support a fragrance-free workplace policy; 20% would not.

As for exposures in public places, I remember following my wife to the top of a department store escalator, stepping off and being sprayed with a strong fragrance by an overexuberant salesperson. I waved her away, but many customers just wave goodbye--20% of the respondents want to leave a business quickly if they smell air fresheners or fragranced products, 18% are unable or reluctant to use public toilets because of scented products, and 14% may forego using soap because they know or suspect the soap is fragranced.

Ingredients? Did you know that a product’s fragrance is typically a mixture of dozens to hundreds of chemicals? I and 46% of those surveyed did not. So too, 65% were unaware fragrance chemicals need not be fully disclosed on the label; about the same number had no idea fragranced products commonly emit hazardous air pollutants--yes, hazardous--and nearly 3 out of 4 respondents mistakenly thought “natural,” “green” and “organic” fragranced products would be free of such hazardous air pollutants.

Wrap Up

Unscented antiperspirant.
What fragrances are added
to cover the scent?

When I shop, I try to find products that are labeled fragrance-free, but some are unscented. They’re the same, right? Nope, not even close. Fragrance-free means no artificial (synthetic) fragrances have been added; you won’t find the word “fragrance” on the ingredient label. Unscented products commonly have added fragrances to mask the smells of other chemicals.

Oh, as far as labels and my wife’s former cosmetic base go, hypoallergenic means only that the product is probably not going to cause an allergic reaction, no guarantee. Sorry about that. But thanks for stopping by.

P.S.
Report on fragrance survey in Air Quality, Atmosphere & Health journal: link.springer.com/article/10.1007%2Fs11869-016-0442-z
Article on study on Science Daily website: www.sciencedaily.com/releases/2016/10/161024095420.htm
Earlier report on volatile product emissions in Air Quality, Atmosphere & Health journal: link.springer.com/article/10.1007%2Fs11869-015-0327-6

Smelling Sense Addendum

I withheld a few items from last Friday’s blog post, Smelling Sense. For one, I didn’t think it was necessary to devote space to the importance of smell for detecting smoke or gas and the consequent need to compensate for olfactory decline or impairment with functioning alarms. Other items, I just didn’t want to spoil your weekend.

Well, it’s Tuesday and I hope you had a pleasant weekend.

Olfaction, Alzheimer’s and Parkinson’s Disease

The loss of the sense of smell may be attributed to various causes, yet there is growing evidence that a decreased ability to correctly identify odors is a predictor of cognitive impairment and an early clinical feature of Alzheimer's. Similarly, olfactory dysfunction, which is commonly associated with Parkinson's disease, is increasingly recognized as an early symptom in the development of the disease.

If you’re on the elderly side and if your sense of smell isn’t up to snuff for reasons unknown, should you panic? Of course not; however, it would be a good idea to have it checked.

And that’s the good news.

Olfaction and Death

The not so good news, based only on a single 2014 study from the University of Chicago, is that olfactory dysfunction may portent death.

To arrive at that conclusion, the investigators gave a smell test with five common scents (rose, leather, orange, fish, and peppermint) to a nationally representative sample of 3,005 volunteers, aged 57 to 85. Five years later, they followed up to determine if the volunteers were still alive. Missing data and undetermined volunteer mortality status reduced the final data set to 2,918 live or deceased volunteers. 

Though not used in the University of Chicago study, the University of Pennsylvania Smell Identification Test is a commonly employed, self-administered test with 40 scratch-and-sniff odors released by pencil tip. The test is available in 15 languages from Sensonics International. (Photo from sensonics.com/smell-identification-test-international-versions-available.html)

The investigators used the data to develop a comprehensive predictive model that controlled for demographics and health factors. Their model estimated that those who could identify no more than one scent (3.5% of the volunteers) were three times more likely to die within 5 years than those who could identify at least 4 scents (nearly 78% of the volunteers). Even those who could identify 2 or 3 scents (nearly 20% of the volunteers) were at elevated risk.

Do the study results mean you’re going to die if you don’t do well on a smell test? No. But if cell regeneration is declining in the olfactory system, it may also be happening in other parts of the body. As noted above for Alzheimer's and Parkinson’s, an impaired sense of smell warrants medical attention.

P.S.

News release from 2014 Alzheimer's Association International Conference: www.alz.org/aaic/releases_2014/sun-830am-smell-eye-tests.asp
Paper on olfaction and Parkinson’s disease in PLOS ONE journal:
journals.plos.org/plosone/article?id=10.1371/journal.pone.0064735
Paper on olfactory dysfunction predicting death in PLOS ONE journal and article on LiveScience website:
journals.plos.org/plosone/article?id=10.1371/journal.pone.0107541
www.livescience.com/48101-loss-of-smell-predicts-mortality.html
Review paper on olfaction and age in Frontiers in Psychology journal: journal.frontiersin.org/article/10.3389/fpsyg.2014.00020/full

Smelling Sense

Welcome back. A recent Berkeley Wellness Alert reminded me that I left you hanging in my blog post Vulture Dining. You may recall the scene:

A formerly live squirrel being examined by a visiting vulture on the street in front of our house in our former neighborhood. I had expected or hoped the bird would remove the dearly departed, but Big Bird surrendered to the passing vehicles and flew off leaving everything in place.

So What Happened, Warren? 

Although it was trash collection day, the truck had already passed. That left it up to me.

I carefully shoveled the remains into a plastic bag, twisted and tied the bag closed, then slipped that bag into another plastic bag, which I also sealed securely. I placed the package into an open trash container in our garage, thinking my job was done. Mistake.

The next day, the pungent odor hinted that I should have covered the container, which I belatedly did. Four days later, the trash was collected; however, weeks later I was still airing and spraying the container to eliminate the reminder.

Olfaction

Smelling a flower. (Photo
from multiple websites)

Before we move on, you might want to clear the air. Think of aromas like your grandmother’s baking, the turkey in the oven, coffee brewing, flowers, baby powder, crayons, chocolate. OK? Ready?

As you likely surmised, the Berkeley Alert reviewed olfaction, the sense of smell. I was surprised the discussion never used the word “dog.” And though it touched on nostrils, noting that one of our two is normally dominant, how could it not mention the ability of rats and moles to smell in stereo, a topic covered in my post Stereo Seeing and Smelling?

Instead, the review was about you and me and our not so unusual sense of smell, which they wrote can detect at least 10,000 different odors. I regret having to point out that a 2014 study from The Rockefeller University and Howard Hughes Medical Institute calculated that number to be more like one trillion!

Olfactory Facts of Interest

Nevertheless, the review emphasized the importance of olfaction, gave a brief summary of the 2004 Nobel Prize winning finding of how we recall and distinguish odors, and offered several other items of interest. For example:

-Women tend to have a keener sense of smell than men.
-The ability to perceive a specific odor declines with continuous exposure to the odor.
-Odors can affect the release of certain neurotransmitters, encouraging mood change, relaxation or even reduced pain; but the effect varies with culture, genetics and associations.
-While many things can temporarily or permanently reduce the sense of smell and might require medical diagnosis, there is a general decline after about age 40. (Hyposmia is a reduced ability to smell; anosmia is a total inability, dysosmia is misperception of smells and phantosmia is olfactory hallucination.)

Searching a bit, I found some additional items I thought were interesting (see P.S.):

-African-Americans and Hispanics begin to experience age-related loss of smelling earlier than Caucasians.
-The sense of smell is the only cranial nerve that can regenerate, and scent cells are renewed every 30 to 60 days.
-We can smell fear and disgust through sweat.
-Every individual has a unique body odor, which, like a fingerprint, might be recognized, for example, by victims of violent crime.

Wrap Up

Beyond all the fond memories of my late mother, I always think of her if I smell mothballs. She would salt the white marbles on stored sweaters and blankets or just about anything that didn’t move. Recently, my brother had a mothball alert, when the departing tenant of a neighboring apartment left mothballs that threatened my brother’s cockatiel. It’s a hair-raising story, but…well, it’s my brother’s story. Thanks for stopping by.

P.S.

University of California, Berkeley Wellness Alert:
www.berkeleywellness.com/self-care/preventive-care/article/making-sense-smell
Nobel Prize statement on the 2004 award to Richard Axel and Linda Buck for their discoveries of odorant receptors and the organization of the olfactory system:
www.nobelprize.org/nobel_prizes/medicine/laureates/2004/illpres/index.html
Science Magazine paper on humans’ ability to discriminate over 1 trillion smells: www.sciencemag.org/content/343/6177/1370
Sense of smell facts on Everyday Health and Mirror websites:
www.everydayhealth.com/news/incredible-facts-about-your-sense-smell/
www.mirror.co.uk/lifestyle/health/20-fascinating-facts-sense-smell-1977351
Psychological Science journal paper on chemosignals communicating human emotions: pss.sagepub.com/content/23/11/1417
The Journals of Gerontology Series A paper on racial disparities in olfactory loss: biomedgerontology.oxfordjournals.org/content/early/2013/05/19/gerona.glt063.full
PLOS ONE journal paper on “nosewitness” identification:
journals.plos.org/plosone/article?id=10.1371/journal.pone.0116706

Depth Perception Photo Addendum

Noting that the freely moving rats in last Friday’s blog post, Stereo Seeing and Smelling, didn’t use stereovision (and the moles were blind), I wanted to illustrate more artistic approaches to capturing depth. Each of the photos featured here can be found on numerous websites, though I’ve tweaked them a bit.

Huge bottle protruding from semi-trailer truck? No--just
 a painted advertisement for a (non-alcoholic) beverage.

A hole blown in the trailer door? No--
just a painted break out.

Mammoth snake squeezing a bus? Yes!

Stereo Seeing and Smelling

Welcome back. Watching the centerfielder make an impossible catch, I flashed back to standing in right field, hearing the crack of the bat, waiting and repeatedly misjudging the whereabouts of fly balls. You guessed that if you read my blog post Sports Talk--Baseball. I described being told after an Air Force physical that I had zero depth perception.

With all due respect to the Air Force, it’s not that bad. I, like most people with two functioning eyes, have stereovision. Each eye sees the same scene from a slightly different perspective, the brain pulls the two views together and…ta-dah…we see the scene in three dimensions.

Seeing 3-D offers advantages besides being a centerfielder or pilot; yet lots of people don’t have stereovision and they get along fine. In case you were wondering, that’s also true of rats. And rats can smell in stereo! I learned that when I learned moles smell in stereo.

Rat’s Non-Stereovision

Although eye coordination in freely moving rats is still unknown, a recently published study from Germany’s Max Planck Institute for Biological Cybernetics found the visual fields of their two eyes are not continuously aligned. As rats run about, their eyes are going in opposite directions.

A cute rat. Note the directions of the
eyes. (photo on multiple websites)

The researchers attached miniature high-speed cameras to rats’ heads and tracked the head position and direction. They determined that the lines of vision of the two eyes didn’t fuse to produce a stereoscopic image but instead varied by as much as 40 degrees horizontally and 60 degrees vertically. (The videos with the paper are great!)

An interesting finding is that, while rats’ eyes are all over the place, they’re always monitoring above. That suggests an adaptation to avoid overhead attack.

Rats Can Smell in Stereo

Although I missed the account in 2006, investigators at India’s National Centre for Biological Sciences showed that rats can use their two nostrils to tell if odors are coming from their left or right.

Confined rats were trained to respond to an odor on their left or right by letting the rats get thirsty, then placing water on the side with the source of the odor. Once trained, the rats needed only a fraction of a second to select the side with the odor regardless of the odor used.

The rats chose the correct side at least 80 percent of the time until one nostril was blocked. Lacking both nostrils for stereo smelling, the rats lost the capability to distinguish the side with the odor.

Moles Smell in Stereo

While the rats were trained and stationary, recent experiments at Vanderbilt University demonstrated that blind moles--common or eastern American (Scalopus aquaticus)--smell in stereo as part of their ordinary search behavior.

In multiple trials, a mole was released into a circular chamber, which had yummy pieces of earthworm placed randomly around the perimeter and whose air pressure could be monitored to determine if the mole sniffed. Within five seconds, the mole would wiggle its nose, sniffing, and go directly to the food.

A cute blind mole. Note the nostrils.
(photo on multiple websites)

To test the importance of stereo smelling, the researcher blocked one nostril. Although the moles still headed toward and eventually found the food, their aim was off toward the side opposite the blocked nostril--left nostril blocked, off to the right; right nostril blocked, off to the left. The same results were obtained in a different chamber where the food was placed directly in front of the entrance.

Next, small tubes were inserted to cross the two nostrils. With right nostril sniffing air from the left and left nostril sniffing air from the right, the poor perplexed little guys just kept searching. If they found the food, it was likely because they relied on the strength of the odor.

Wrap Up

I hope you enjoyed this peek into the world of rats and moles and that your own vision and olfactory capabilities are performing well. Thanks for stopping by.

P.S.

- Links to rat vision study in journal Nature (URL must be pasted in) and Science Daily:
www.nature.com/nature/journal/v498/n7452/full/nature12153.html
www.sciencedaily.com/releases/2013/05/130527100530.htm
- Links to rats’ stereo smelling study in Science magazine and Nature News:
www.sciencemag.org/content/311/5761/666.abstract
www.nature.com/news/2006/060130/full/news060130-10.html
- Links to moles’ stereo smelling study in online journal Nature Communications, Research News at Vanderbilt and National Geographic:
www.nature.com/ncomms/journal/v4/n2/full/ncomms2444.html
news.vanderbilt.edu/2013/02/moles-smell-in-stereo/
news.nationalgeographic.com/news/2013/02/130205-moles-smell-stereo-animals-weird-science/