Don't ignore the loss of taste and smell

It can cause malnutrition, marital discord, and other problems. Gastric reflux, an overlooked infection, or a drug you've prescribed may be the culprit.

Clinicians combat heart disease, stroke, diabetes, and infections in their practices every day, so complaints about deficiencies in smell and taste may not seem important. But they can be.

Patients with compromised smell and taste senses can experience family discord and expose themselves and others to danger because they cannot detect spoiled food, leaking gas, or smoke. Those who no longer enjoy eating lose weight and suffer nutritional deficiencies. Smell and taste deficits warrant treatment, and the proper approach depends on which sense is impaired and why.

Mary complained of inability to taste. “Foods taste flat, and I just don't enjoy eating. That's why I avoid going out and would rather cook at home. I have problems there, though, because my family says my cooking is getting worse. Of course, I know the reason.”

Intensive laboratory testing revealed that Mary had lost a great deal of taste sensation, and questioning uncovered a recent severe respiratory infection. Infections—viral as well as bacterial— can injure not only the taste receptors in our mouth but also our sense of smell. All is not lost for Mary, though. Nerve elements exposed to a virus can recover in many cases.

In addition to viruses such as the one Mary suffered from, exposure to toxic products and pollutants can alter taste.

Consider this case:
John, a farmer and a heavy cigarette smoker, was depressed because food had very little flavor to him. He enjoyed only food that had been heavily seasoned with extra pepper or a sharp sauce. This lack of interest in dining had led to weight loss.

Laboratory investigation of John's complaint found a markedly diminished smell sensation. There is no doubt that smoking and exposure to pesticides on the farm contributed to his problem. When John stopped smoking, used a mask while working around the farm, and got help with spraying crops, his sense of smell improved and, in turn, his difficulty tasting flavors diminished.

Facts about flavor

Sensations arising from taste buds are mostly sweet, sour, bitter, or salty. When odorants pass through the mouth to the back of the throat, they stimulate nerve receptors, resulting in the production of flavor. Smell sensations help us to tell the difference, for example, between vanilla, raspberry, and licorice substances.

How early do we see flavor sensitivity in children? When facial and sucking responses were studied in infants, researchers found that sweet solutions increased sucking action. Salty solutions led to different facial reactions and decreased sucking activity. It is therefore evident that flavor and taste are well- developed at birth.1

Early sensory experiences from mother's milk certainly influence later preferences. Testing has shown that infants exposed to carrots in mother's milk over a period of several weeks enjoyed carrot-flavored cereal more than plain cereal as compared with babies whose mothers avoided carrots. Human milk is rich in flavors that reflect the mother's ingestion of such things as garlic, alcohol, and carrots. Cigarettes and alcohol diminish the flavor of milk. Babies have been noted to breastfeed less with mothers who have been drinking alcohol, but this appears to be more the result of depressed milk production than lack of interest on the part of the baby.2

Flavor aversion

Deliberate avoidance of certain substances because of perceived unpleasant taste and flavor is termed “flavor aversion.” This can be a protective mechanism in that rotting food and toxic products are set aside. Patients learn to avoid certain foods that in the past have caused stomach upsets, headaches, or even a skin eruption. More severe sensitivities can lead to appetite and weight loss. Cancer, alcohol, tobacco, and exposure to certain drugs can influence flavor and lead to subsequent aversion.3

Heather complained of a bad taste and impaired flavor that were causing her to avoid many foods and shun dining out.

Investigation revealed that she had been taking the antibiotic clarithromycin (Biaxin) for an infection. Biaxin is an excellent medication, but it can occasionally cause an unpleasant taste in the mouth. When the medication was stopped, Heather's ability to taste gradually returned.

Other commonly used medications that can cause taste and flavor difficulties are allopurinol, captopril, enalapril, nitroglycerin, diltiazem, dipyridamole, nifedipine, hydrochlorothiazide, lisinopril, lithium, lovastatin, and levodopa.

Underlying causes

Stomach disturbances can cause diminished flavor or an annoying bad taste. When gastric reflux is to blame, heartburn and indigestion can provide diagnostic clues. In many cases, the cause is laryngopharyngeal reflux, in which there are no stomach complaints, just redness and swelling of the larynx. Patients may complain of constant throat clearing, hoarseness, and cough. Endoscopy may be unrevealing.

Chemical exposure can impair taste and the perception of flavor. In the past, silver-jewelry workers have suffered disturbances in flavor because of exposure to lead fumes. Steelworkers, brass foundry workers, and, as previously noted, persons exposed to pesticides can have their taste reduced.

Aging may also cause diminished taste and resultant flavor problems, to such an extent that the elderly are sometimes considered “fussy eaters.”

Neurologic problems can present initially with complaints of lack of smell and subsequent complaints of taste and flavor distress. Often, one of the first complaints of patients with Alzheimer's disease is “I have lost my sense of smell.”

Occasionally, injuries to the head (concussion) can result in abnormalities of taste and flavor. However, this occurs in only about 0.5% of cases. Surgical procedures of the head and neck can interfere with the nerves responsible for taste. The chorda tympani nerve, which is responsible for taste in the front portion of the tongue, can be stretched or severed during surgery on the middle ear.

Dentists extracting the third molar can cause lingual nerve injury resulting in taste complaints. Bronchoscopy, laryngoscopy, and tonsillectomy can result in subsequent complaints of flavor dysfunction due to involvement of the lingual and glossopharyngeal nerves. Radiation therapy affecting certain nerves can lead to taste and flavor impairment. Salivary-gland disruption and infections in the mouth can be complicating features.

Unforeseen effects

An elderly man and his wife, who had been happily married for 45 years, were experiencing marital problems. The husband had several complaints, the main one having to do with his wife's cooking. Nothing pleased him. Food tasted flat. Even the aroma of cooking food upset him and was unappealing. Some foods actually had what he termed a “disgusting taste.” His nose constantly felt congested.

Examination and testing found polyps that blocked the man's nasal canals, diminishing his sense of smell and, in turn, his sense of taste. When the polyps were removed, marital harmony was restored.

While marital difficulties are not life-threatening, other effects of smell and taste difficulty can present danger. As previously noted, the inability to smell smoke, leaking gas, or chemicals and the inability to taste spoiled food can put patients and others around them at risk. Cardiac patients on restricted diets may add excess salt to their food when it appears deficient, and diabetics may add extra sugar when flavor appears absent.

Chefs, bakers, wine tasters, and others may have their livelihoods threatened when taste and flavor are impaired. Anxiety and depression often result and require medical assistance. Even when a patient seeks help, his clinician may not realize the impact taste deficiency can have.

Providing help

Any patient who complains of smell and taste difficulties should have a thorough examination. A careful history can uncover exposure to toxic materials. The staff at our taste and smell clinic includes an internist for medical evaluation, ENT specialist, neurologist, and dentist, as well as a specialist in smell and taste testing.

When viral infections and head injury cause taste problems, tincture of time can lead to recovery. Estimates as to percentages of total recovery have varied from 8% to 39%.

Nasal problems such as congestion, polyps, and sinusitis have a better prognosis. Use of steroid nasal sprays and surgery have brought about dramatic changes for these patients. With improvement in smell status, flavor problems diminish or disappear. Patients whose taste disturbances are linked to gastric problems may find that medications such as proton-pump inhibitors can be very effective in eliminating reflux associated with bad flavor and bad taste.

Patients do not have to live with persistent bad flavor and taste difficulties. Facilities now exist for improving their life and its pleasures.

Dr. Mann is assistant professor of internal medicine and director of the Taste and Smell Center at the University of Connecticut, in Farmington.

References

1. Bernstein I. Flavor aversion. In: Getchell TV, Doty RL, Bartoshuk LM, Snow JB, eds. Smell and Taste in Health and Disease. New York, N.Y.: Raven Press; 1991:417-428.

2. Ganchrow JR, Mennella JA. Ontogeny of human flavor perception. In: Doty RL, ed. Handbook of Olfaction and Gustation. New York, N.Y.: Marcel-Decker Inc.; 2003:823-846.

3. Kiefer SW, Rusiniak KW, Garcia J. Flavor-illness aversions: gustatory neocortex ablations disrupt taste but not taste-potentiated odor cues. J Comp Physiol Psychol. 1982;96:540-548.

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