The Importance of Smell
I just posted an article on my website on the power of olfaction and its link to our health, as well as our mortality. Specially, the sense of smell is intricate for human survival. It modulates appetite and food preferences, is important for detection of danger in the environment, is involved in pain processing and the stress response, effects social relationships, and has a profound impact on our emotions, memory, and physiological responses. Furthermore, several studies have reported on the link between loss of smell and aging, cognitive decline, and increase risk of death from all causes. Thankfully, even without the sense of smell, essential oils and odors have an interesting correlation to modulating the same processes as olfaction alone, but in different ways. In this blog, I’ll use the example of Parkinson’s Disease (PD).
A Quick Background on Parkinson’s Disease
Scientists believe PD is a result of the combination of environmental, genetics, and epigenetic factors (how the environment effects gene expression). Many studies have linked abnormal alpha-synuclein, clumps of proteins found in the brain and other tissues, to the disease process. In fact, accumulation in the gastrointestinal tract of this protein is becoming a studied brain-gut etiology. The World Journal of Gastroenterology states the following on these links as well as the connection to smell being an indicator of this disease:
The classical motor symptoms like bradykinesia, resting tremor, rigidity and late postural instability result from the death of dopamine-generating cells in the substantia nigra. There is also a wide spectrum of non-motor manifestations involving for example olfactory (loss of smell), gastrointestinal (GI), cardiovascular, and urogenital systems [3]. It has become evident that the different levels of the brain-gut axis including the autonomic nervous system (ANS) and the enteric nervous system (ENS) may be affected in PD [4-8]. (bold emphasis mine)
The Smell Connection of Detection
Science Daily reported:
Now, a new laboratory model of Parkinson’s is giving scientists an inside look at what happens in the brain years before motor symptoms appear. Specifically, it demonstrates how abnormal alpha-synuclein proteins, which are strongly associated with Parkinson’s, gradually spread from an area of the brain implicated in the early stages of the disease to other regions of the brain ultimately damaged by the disease. The findings were published today in the Journal of Experimental Medicine.
The article continues:
“We know that specific signs of Parkinson’s, including a loss of sense of smell, appear years before the onset of motor symptoms. Our new model replicates the phase that occurs long before diagnosis and, importantly, gives us a powerful tool to test novel interventions that might prevent the onset of Parkinson’s as we know it.”
The study demonstrates that alpha-synuclein travels along nerve cells in the olfactory bulb — the part of the brain that controls sense of smell — prior to the onset of motor symptoms and that this area may be particularly susceptible to the spread of alpha-synuclein, ultimately causing deficits in the sense of smell. Clumps of alpha-synuclein eventually reach several additional brain regions, including the brainstem area that houses dopamine cells. (bold emphasis mine)
The researchers are hoping these findings will lead to a new model to study PD. However, there has been causative agents explored previously.
The Environmental Effect of Smell on PD
There have been prior reports of the connection between olfaction, environmental triggers, and Parkinson’s disease. This theory is termed the “olfactory vector hypothesis.” Annals of Neurology
explains:
Environmental agents, including viruses, prions, and toxins, have been implicated in the cause of a number of neurodegenerative diseases, most notably Alzheimer’s and Parkinson’s diseases. The presence of smell loss and the pathological involvement of the olfactory pathways in the formative stages of Alzheimer’s and Parkinson’s diseases, together with evidence that xenobiotics, some epidemiologically linked to these diseases, can readily enter the brain via the olfactory mucosa, have led to the hypothesis that Alzheimer’s and Parkinson’s diseases may be caused or catalyzed by agents that enter the brain via this route. Evidence for and against this concept, the “olfactory vector hypothesis,” is addressed in this review.
In other words, the sense of smell can be an entry way to toxicants through the nose to the brain and throughout the body! However, there’s good news for aroma inhalation as well!
The Essential Oils Connection
Essential oils have the ability to modulate emotion, memory, and physiological responses through their aroma and also due to their powerful secondary metabolites. Furthermore, essential oils have the power to modulate the health of the gut and brain. In fact, there’s information on my essential oils database on how oils can modulate many aspects of health and my latest blog discusses how even without the sense of smell, odorants have powerful effects.
So, make sure you check it out for more information. For now, know that by using essential oils, you are powerfully practicing preventative medicine through the linkage of your nose to your brain and supporting your gut-brain connection.
References
Hays NP, Roberts SB. The anorexia of aging in humans. Physiol Behav. 2006;88: 257-266. doi:
10.1016/j.physbeh.2006.05.029
Jacob S, Garcia S, Hayreh D, McClintock MK. Psychological effects of musky compounds: comparison of androstadienone with androstenol and muscone [abstract]. Horm Behav. 2002; 42: 274-283. doi: 10.1006/hbeh.2002.1826
Fox K. The Smell Report. Social Issues Research Center. http://www.sirc.org/publik/smell.pdf
Krusemark EA, Novak LR, Gitelman DR, Li W. When the Sense of Smell Meets Emotion: Anxiety-State-Dependent Olfactory Processing and Neural Circuitry Adaptation. The Journal of Neuroscience. 2013;33(39):15324-15332. doi:10.1523/JNEUROSCI.1835-13.2013.
Corradi-Dell’Acqua C, TuscheA, Vullieumier P, Singer T. Cross-modal representations of first-hand and
vicarious pain, disgust and fairness in insular and cingulate cortex. Nature Communications. March 18, 2016. doi:10.1038/ncomms10904
Masaoka Y, Sugiyama H, Katayama A, Kashiwagi M, Homma I. Slow breathing and emotions associated with odor-induced autobiographical memories. Chem Senses. 2012 May;37(4):379-88. doi: 10.1093/chemse/bjr120.
Vermetten E, Schmahl C, Southwick SM, Bremner JD. A Positron Tomographic Emission Study of Olfactory Induced Emotional Recall in Veterans with and without Combat-related Posttraumatic Stress Disorder. Psychopharmacology bulletin. 2007;40(1):8-30.
Gottfried JA. Central mechanisms of odour object perception. Nature reviews Neuroscience. 2010;11(9):628-641. doi:10.1038/nrn2883.
Van Andel Research Institute. New model recreates early spread of Parkinson’s disease in the brain. Science Daily. August 8, 2016. https://www.sciencedaily.com/releases/2016/08/160808163628.htm
Mulak A, Bonaz B. Brain-gut-microbiota axis in Parkinson’s disease. World Journal of Gastroenterology:WJG. 2015;21(37):10609-10620. doi:10.3748/wjg.v21.i37.10609.
Nolwen L. Rey, Jennifer A. Steiner, Nazia Maroof, Kelvin C. Luk, Zachary Madaj, John Q. Trojanowski,
Virginia M.-Y. Lee, Patrik Brundin. Widespread transneuronal propagation of α-synucleinopathy triggered in olfactory bulb mimics prodromal Parkinson’s disease. The Journal of Experimental Medicine, 2016; jem.20160368 DOI: 10.1084/jem.20160368
Chamine Irina and Oken Barry S. Aroma Effects on Physiologic and Cognitive Function Following Acute Stress: A Mechanism Investigation. The Journal of Alternative and Complementary Medicine. June 2016. doi:10.1089/acm.2015.0349.
Doty R. The olfactory vector hypothesis of neurodegenerative disease: Is it viable? Ann Neurol.2008;63:7-15
Prediger RDS, Aguiar AS, Matheus FC, et al. Neurotox Res. 2012; 21: 90. doi:10.1007/s12640-011-9281-8
Misra BB, Dey S. TLC-bioautographic evaluation of in vitro anti-tyrosinase and anti-cholinesterase potentials of sandalwood oil. Nat Prod Commun. 2013 Feb;8(2):253-6.
Fernández LF, Palomino OM, Frutos G. Effectiveness of Rosmarinus officinalis essential oil as antihypotensive agent in primary hypotensive patients and its influence on health-related quality of life. J Ethnopharmacol. 2014;151(1):509-16. doi: 10.1016/j.jep.2013.11.006. Epub 2013 Nov 20.