By Dr. Mercola
Inside your nasal passages are two odor-detecting patches made up of about 6 million cells known as olfactory receptors. These allow you to detect thousands of different smells, and although other animals' senses of smell are far more acute (a dog has 220 million olfactory receptors, for comparison), a human's sense of smell is still remarkably sensitive.1
For instance, humans can detect certain substances in air even when they're diluted to less than one part in several billion, according to the Social Issues Research Center's (SIRC) Smell Report.2
Your sense of smell is intricately tied to your emotions, your ability to taste, and even sexual attraction… and it's also intricately tied to your health.
According to some research, your sense of smell may peak at age 8 and start to decline in sensitivity by the age of 15. Other studies suggest smell sensitivity begins to deteriorate from your early 20s.3
That being said, healthy 80-year-olds have been found who have just as keen an ability to smell as much younger adults, which suggests that your sense of smell doesn't just degrade as a matter of course, but rather may be dependent on your overall physical and mental health.4
New research, in fact, showed that smell is a powerful "canary in the coalmine" for predicting your future longevity, and if you lose yours, it's a very bad sign…
Losing Your Sense of Smell May Predict Death Within Five Years
Olfaction, or sense of smell, is strongly linked to many diverse physiological processes, and so researchers from the University of Chicago set out to determine if it is a harbinger of five-year mortality.
Using data from a nationally representative sample of more than 3,000 older US adults, the study found those with an inability to perceive odor (known as anosmia) were more than four times as likely to die in five years, compared to those with a healthy sense of smell.5
Specifically, 39 percent of the participants who failed the first smell test (which consisted of identifying five common scents) died in the next five years, compared to 19 percent of those who had moderate smell loss and 10 percent of those with a healthy sense of smell.
Why Might Your Sense of Smell Serve as a Bellwether of Your Health?
A loss of the sense of smell was a remarkably strong indicator of approaching death, even more so than known leading causes of death, and independent of known risk factors like nutrition, cognitive function, mental health, smoking, alcohol abuse, or frailty.
Loss of sense of smell was a stronger predictor of death than even a diagnosis of cancer, heart failure, or lung disease.6 Loss of olfactory function is probably not a cause of death, but rather may "serve as a bellwether for slowed cellular regeneration or as a marker of cumulative toxic environmental exposure," the researchers said.
As The Guardian reported:7
"The tip of the olfactory nerve, which contains the smell receptors, is the only part of the human nervous system that is continuously regenerated by stem cells.
The production of new smell cells declines with age, and this is associated with a gradual reduction in our ability to detect and discriminate odors. Loss of smell may indicate that the body is entering a state of disrepair, and is no longer capable of repairing itself.
The olfactory nerve is also the only part of the nervous system that is exposed to the open air. As such, it offers poisons and pathogens a quick route into the brain, and so losing smell could be an early warning of something that will ultimately cause death."
Check for Zinc Deficiency if You Are Losing Your Sense of Smell
Zinc, an essential trace mineral, is required to produce an enzyme called carbonic anhydrase (CA) VI, critical to taste and smell, which is why loss of sense of smell is one of the classic signs of chronic zinc deficiency. This might be yet another reason why a dwindling sense of smell is linked to impending death, as zinc is important for a number of life-sustaining functions, including:
- Strong immunity
- Important component of the enzymes involved in tissue remodeling and prevention of cancer
- Maintenance of your mood, mental clarity, and restorative sleep
- Prostate and intestinal health
Zinc is a constituent of at least 3,000 different proteins in your body and a component of more than 200 different enzymes. In fact, zinc is involved in more enzymatic reactions in your body than any other mineral.
Zinc increases your production of white blood cells and helps them fight infection more effectively. It also increases killer cells that combat cancer, helps your immune system release more antibodies, and supports wound healing.
Mild zinc deficiency is relatively common, especially in infants and children, pregnant or breast-feeding women, elderly, people with poor gastrointestinal absorption or bowel disease like Crohn's disease, and for those eating vegetarian or vegan diets. A number of factors contribute to the overall problem of zinc deficiency:
- Years of industrial farming practices, such as monocropping (planting large expanses of land with the same crop year after year) and tilling the soil, have left our soils deficient in natural minerals, like zinc.
- Certain drugs deplete your body of zinc, such as ACE inhibitors, thiazide diuretics, and acid-reducing drugs like Prilosec and Pepcid.
- Certain diets, such as vegetarian/vegan diets and high-grain diets, are low in bioavailable zinc and high in phytic acids, which impair zinc absorption.
If you are deficient in zinc, your body may become less able to repair genetic damage caused by oxidative stress. Having low levels of zinc has even been found to cause strands of DNA to break and studies have linked zinc deficiency to various types of cancer, infection, and autoimmune diseases.
Along with frequent infections, such as cold and flu, and a diminishing sense of smell, white spots on your fingernails can indicate you're not getting enough zinc.
What Are the Best Food Sources of Zinc?
For adults, the RDA for zinc is about 11 milligrams per day for adult men and 8 milligrams for women. If you are lactating or pregnant, you need about 3 mg more. For children, 4-8 year olds need about 5 mg, and 9-13 year olds need 8 mg, while infants need only about 3 mg. Good sources of dietary zinc include meats, oysters and wild-caught fish, raw milk, raw cheese, beans, and yogurt or kefir made from raw milk.
If you are healthy and you eat a well-balanced diet, you will rarely need supplements to complete your body's zinc needs, and you should strive to get zinc from dietary sources. Taking too much zinc in supplement form can be dangerous, as it can interfere with your body's ability to absorb other minerals, especially copper. If you decide to use a zinc supplement, chelated forms are better absorbed than inorganic forms, or zinc salts.
Tips to Improve Your Sense of Smell
About 3 million to 4 million Americans have been diagnosed with anosmia (a complete inability to smell) or hyposmia (a reduced ability to smell).8 If you notice your sense of smell slipping, and you know you're not zinc deficient, there are steps you can take to improve it. First, I'd suggest reading through my nutrition plan for a comprehensive dietary plan that will support your health on multiple levels. Next, try these tips that are known to boost your sense of smell:9
- Exercise: Research shows that the more you exercise, the less likely you are to develop problems with your sense of smell as you age. Exercising even one time a week was found to reduce the risk of losing your sense of smell.10
- Become scent conscious: Make a point to smell your food before you eat it, and notice the scent of flowers, cut grass, or even rain. Doing this regularly will help increase your sense of smell.
- Try "sniff therapy": Choose three or four different scents, such as floral, fruity, and coffee. Sniff them four to six times a day, which will help the different receptors in your nose to work better.
How to Use Your Sense of Smell to Your Advantage
If your sense of smell is working fine, why not use it to your advantage? Through the use of aromatherapy, you can harness certain scents that trigger real physical and emotional responses. For instance, research shows:
- A systematic review of 16 randomized controlled trials examining the anxiolytic (anxiety-inhibiting) effects of aromatherapy among people with anxiety symptoms showed that most of the studies indicated positive effects to quell anxiety (and no adverse events were reported).11
- People exposed to bergamot essential oil aromatherapy prior to surgery had a greater reduction in pre-operative anxiety than those in control groups.12
- Sweet orange oil has been found to have anxiety-inhibiting effects in humans, supporting its common use as a tranquilizer by aromatherapists.13
- Ambient odors of orange and lavender reduced anxiety and improved mood in patients waiting for dental treatment.14
- Compared to the controls, women who were exposed to orange odor in a dental office had a lower level of anxiety, a more positive mood, and a higher level of calmness. Researchers concluded, "exposure to ambient odor of orange has a relaxant effect."15
Anxiety, of course, is only one use for aromatherapy. Other potential uses are varied and include the following:
- Green apple scent for migraines: One study found that the scent significantly relieved migraine pain. This may also work with other scents that you enjoy so consulting with an aromatherapist might be beneficial.
- Peppermint for memory: The aroma of peppermint has been shown to enhance memory and increase alertness.
- Nausea and vomiting: A blend of peppermint, ginger, spearmint, and lavender essential oils has been found to help relieve post-operative nausea.16
- Lavender for pain relief: Lavender aromatherapy has been shown to lessen pain following needle insertion.17