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Geneseo Republic - Geneseo, IL
  • What's Up Doc? Investigating the loss of taste

  • Q: My brother said he ate some kind of nut and it messed up his sense of taste. Is this possible?

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  • Q: My brother said he ate some kind of nut and it messed up his sense of taste. Is this possible?
    A: Some of the cells that cover our tongue and other parts of the oropharynx (our 10,000 plus taste buds) are stimulated by saltiness, sweetness, sourness, bitterness, savoriness (also called umami, imparted by glutamate) and/or chalkiness (imparted by calcium salts). These modified epithelial cells regenerate every 10 days. The signals generated by this stimulation are carried by cranial nerves -- nerves that emerge directly from the brain and are abbreviated as CN –– VII, IX or X. For comparison, smell utilizes CN I, sight uses CN III, hearing uses CN VIII and touch uses multiple non-cranial nerves.
    The sense of smell is closely related to the sense of taste. Here is a home experiment you can do to demonstrate this: pinch your nose and put a little bit of cinnamon (liquid cinnamon is best, but powder will work, too) on the tip of your tongue and be sure not to accidentally smell it… Cool, huh?
    Over 100 million neuro-epithelium cells in the nose and nasal passages sense volatile chemicals from airborne molecules. The signals from this stimulation are carried to the brain via CN I. These cells regenerate every one to two months.
    Peripheral effects (affecting the reception or transmission of the signals) or central causes (affecting the brain's interpretation of these signals) can decrease, eliminate or alter/distort the normal function of the sense of smell or taste.
    The most common thing that alters taste is actually alterations of smell (be sure to do the cinnamon experiment to understand this), accounting for up to 75 percent of reported altered taste complaints. Infectious or inflammatory processes affecting the nose/nasal passages (such as colds, sinus infections, cocaine abuse, blockages from masses such as tumors or cysts and many other conditions) are the most common conditions affecting the sense of smell. Transmission or interpretation of the smell signals can be affected by congenital conditions, such as Kallman's syndrome, certain diseases, such as multiple sclerosis or some endocrine diseases, strokes, seizures and other conditions.
    There are many things that can directly affect the taste receptors, signal transmission or signal interpretation including oral surgery, infectious/inflammatory conditions (i.e. poor oral hygiene, dental abscesses and radiation therapy), normal aging changes to taste bud function, endocrine conditions (i.e. thyroid disease, adrenal disease or diabetes), systemic diseases (i.e. amyloidosis), toxicities from certain medications or foods (i.e. "pine nut mouth"), certain mineral deficiencies (i.e. zinc, copper or nickel deficiencies), strokes and other central nervous system processes.
    Overall, altered sense of smell or taste is not uncommon; one survey found about 3 million Americans have some problem affecting smell sensation each year, and 1 million have something affect their sense of taste. Over two-thirds of us will have some condition affect our sense of smell and/or taste at some time in our lives.
    Page 2 of 2 - Most of these conditions manifest as decreases in the acuity of smell or taste. However, distortion of these senses can also occur. Parosmia is the perception of an unpleasant smell when no adverse odorant is causing it, and cacoguesia is the perception of a bad taste that is not due to a specific substance. An example of cacoguesia is metalloguesia, the abnormal sensation of a metallic taste.
    Pine nuts have been known to cause cacoguesia; although it is uncommon (so no need for everyone to stop eating pine nuts), there have been many case reports of it. In fact, after several cases traced back to one batch of pine nuts in Europe, the Brussels Poison Centre did some testing, but was unable to isolate any pesticide or heavy metal contamination that could have been the cause. Pine nut mouth manifests as an unpleasant taste worsened by many, and sometimes all, foods a day or so after pine nut ingestion. This typically worsens by day two or three and then resolves on its own over one to two weeks.
    Patients who develop an altered sense of smell or taste require a complete history and physical examination to determine if any testing needs to be done or if watchful waiting for the symptoms to resolve on their own is the best strategy. Endocrine testing, imaging of the sinuses or brain (i.e. MRI or CT) and other evaluations may be considered. Treatment is aimed at addressing any underlying condition that is identified.
    Jeff Hersh, Ph.D., M.D., F.A.A.P., F.A.C.P., F.A.A.E.P., can be reached at DrHersh@juno.com.
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