The Smell of Health and Aging – How Essential Oils and Odorants Support the Body, Even with Ansomia (Loss of Smell)
The Many Physiological and Health Implications of Smell
Olfaction is a diverse and intricate part of our human functioning. The sense of smell has been shown to modulate appetite and food preferences, play a role in detection of danger, impact social relationships, and exhibit profound effects on our emotions, memory, and physiological responses.
I recently completed a research review on the neuroanatomy of olfaction, linking it to many of these powerful modulatory activities. The interconnections and pathways are complex. I will save you the major details in this blog and get to the point, but don’t worry, I will give you a link to the journal when it is released. Basically, the main area of the brain that links olfaction and emotion is the amygdala. This group of nuclei in the brain are also involved in pain processing and the stress response. This means that with one sniff, mood, discomfort, and nerves can all be effected simultaneously!
Furthermore, exposure to smells have been documented to ignite vivid associative memories that is based on the experiences of the sniffer. These remembrances can then create biological responses, including effects on our breathing patterns and heart rate.
When You Can’t Smell
All of these interactions make the sense of smell powerful for human health, but what happens when the sense of smell is hindered? There is actually a medical condition called anosmia, which is defined as the inability to smell. However, the range of loss of smell can vary.
The true prevalence of smell disorders is not well-known. This is due to underreporting and sufferers becoming accustomed to their diminished sense. Currently, the National Institute on Deafness and Other Communication Disorders (NIDCD) estimates about two percent of North Americans suffer with it. However, a more recent National Health and Nutrition Examination Survey (NHANES) from 2011 to 2012 suggested approximately 10% of Americans had struggle with smell dysfunction.
Anosmia can be temporary, such as from the common cold and can resolve with other systematic symptoms. However, it can become “permanent” from chronic irritation, inflammation, and damage to the mucosal lining of the nose (e.g.; chronic sinusitis, hay fever, etc.) Other causes can range from obstructions (e.g.; polyps or bony deformations), neurological issues, genetics, metabolic diseases (diabetes, circulatory issues), autoimmunity, infections, injury, head trauma, malnutrition, medications (side effects and toxicities), smoking, injury, nutritional deficiencies/excesses (zinc*), and more.
*A Side Note on Zinc
Several nutrient deficiencies have been linked to anosmia, most often zinc. However, the nasal application of zinc has evidence of its association with damage to the nasal tissue, causing loss of smell in some individuals. Therefore, it is best to test for zinc deficiency prior to using high doses for smell loss.
The Smell of Aging
A deterioration in olfaction function is common in aging and not necessarily linked to any pathology. According to eMedicine on Medscape, “These olfactory bulb losses may be secondary to sensory cell loss in the olfactory mucosa and/or general decline in the regenerative process from stem cells in the subventricular zone” (SVZ). Other research also hints that the exact mechanism of decline in odor detection with aging is up for debate. A review in 2014 in Trends in Neuroscience states:
It is apparent that the mechanisms underlying aging-related deficits in olfactory acuity, discrimination, or sensitivity remain to be determined (Box 2). Although incremental age-associated changes are recognized in neurogenesis in both the epithelium and SVZ, neither these nor the changes in synapse number seem sufficient to fully account for behavioral changes occurring during normal aging.
The Smell of Aging and Survival
Interesting, right? How smell decreases with aging and getting older is linked to well…death. I mean, no one gets out of life alive. Still, is there science to support this link? You bet.
In a recent study in PLoS One that included a nationally representative sample of 3,005 older U.S. adults (57-85 years), olfactory dysfunction was studied to see if it could be used to determine mortality rate over five years. The subjects were assessed in two waves. In Wave 1 (2005-2006), olfactory dysfunction was determined objectivity. In Wave 2 (2010-2011), measurements in Wave 1 were used to estimate all-cause mortality, controlling for demographics and health factors.
It was found that individuals with anosmia had over three times the odds of death (39%) compared to normal smelling individuals (10%). The authors reported this was independent of leading causes of death, “and did not result from the following mechanisms: nutrition, cognitive function, mental health, smoking and alcohol abuse or frailty.” There was; however, a slight interaction with sex, frailty, and cognitive deficits modulating the risk for mortality, but not diminishing the main effect of increased overall risk of anosmia alone. The authors report:
Olfactory function is thus one of the strongest predictors of 5-year mortality and may serve as a bellwether for slowed cellular regeneration or as a marker of cumulative toxic environmental exposures. This finding provides clues for pinpointing an underlying mechanism related to a fundamental component of the aging process.
More Links to Smell Loss and Deterioration
Interestingly, the olfactory system has also been implicated to be a warning signal for Alzheimer’s disease. Alzheimer’s.net reports:
Researchers at The University of Florida asked over 90 participants to smell a spoonful of peanut butter at a short distance from their nose. Some participants had a confirmed early stage Alzheimer’s diagnosis, some had other forms of dementia, while others had no cognitive or neurological problems.
Of those participants, only those with a confirmed diagnosis of early stage Alzheimer’s had trouble smelling the peanut butter. Additionally, those patients also had a harder time smelling the peanut butter with their left nostril. Generally, the right nostril was able to smell the peanut butter 10 centimeters farther away than the left nostril. The difference in smell between left and right nostril in unique to the disease.
So, are people with anosmia doomed to higher risk of death and cognitive decline.
Not necessarily, as stated in the study on mortality, it is a risk factor with many interactions, furthermore, smell has effects “beyond the nose.”
Sniffing-Out Orders Beyond Smell
Do people still get benefit from essential oils with anosmia (inability to smell)?
The more I dug into the research, the more I was amazed by what using our nose could accomplish! Of course, I was most delighted by how essential oils, in addition to their aromatic qualities, contain potent secondary metabolites which affect our physiology and biology beyond their ability to smell pretty.
I discussed four reasons why being around the scent of essential oils is more than a pleasant aroma in this blog. These included their effects on:
- immune modulation and tumor inhibition
- stress relief
- social relationships
Furthermore, essential oils can impact memory, digestive health (absorption of nutrients), act as antioxidants (toxin exposure protection), balance hormones (along with stress), and modulate the nervous system.
If you still think “aromatherapy” is only about smelling pretty odors to relax, here are some resources that dive deep into the biochemistry of secondary metabolites:
- This book describes different production techniques, chemistry, and sensory properties of essential oils.
- Page 82 starts a discussion on secondary metabolites and quality control.
- There’s also an interesting section on ways to find enantiomers and the importance of plant preparation. (Scroll to the essential oils sections starting on page 57, some pages are not available in this preview)
- This book is on the chemistry and production of essential oils.
A New Way Odors Could Affect the Body
In a 2014 article, it was noted that odor receptors where found throughout the body, not just the nose. The article discusses how odor receptors have been found in the skin (think topical application of essential oils), testes, prostate, muscles, lungs, and more. Though most studies are in vitro and in vivo, it is has raised the possibility of how odors have more effect than through their aroma. In fact, the article states:
Olfactory receptors are the largest subset of G protein-coupled receptors, a family of proteins, found on the surface of cells, that allow the cells to sense what is going on around them. These receptors are a common target for drugs — 40 percent of all prescription drugs reach cells via GPCRs — and that augurs well for the potential of what might be called scent-based medicine.
Recently, a pretty amazing study in Science Daily showed another way that odor could affect the body. It reported that scientists had discovered new olfactory receptors in the lungs! The experimenters choose a banana-apricot scent as the odor. The article summary states:
Researchers identified two types of olfactory receptors in human muscle cells of bronchi. If those receptors are activated by binding an odorant, bronchi dilate and contract — a potential approach for asthma therapy…
The newly discovered receptors in muscle cells are named OR2AG1 and OR1D2. The researchers also identified the activating odorous molecules as well as the signalling pathways that are triggered in the cells.
This finding could provide an additional and noteworthy explanation on how essential oils modulate physiological responses.
In addition to their secondary metabolites effecting cellular processes, essential oils could bind to various receptors in the organs in the body causing direct stimulation or calming!! Wow!
This is yet another amazing example of how aroma and essential oils are a powerful tool for supporting health and well-being, maybe beyond what we thought…or I mean, smelled!
This blog is a continuation of my recent e-blasts to my essential oils subscribers. I posted an updated version on The Power of Smell- Beyond the Nose, which was Part II in a series here. You can get the e-blasts, with some exclusive content for free by being on my e-subscriber list.
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