Understanding Taste Dysfunction in Patients with Cancer

Presented by Norman Swope, BSN RN

Written By Laura McLaughlin, RN, PhD, and Suzanne M. Mahon, RN, DNSc, AOCN, APNG.Clinical Journal of Oncology Nursing, Volume 16, Number 2, pp171-78.

1.5 hours

Five Senses

• 1. Vision • 2. Hearing• 3. Touch• 4. Smell • 5. Taste

Four taste Modalities

• 1. Sweet 2. Sour 3. Salty 4. Bitter

• Combinations of those basic tastes aid in the recognition of the millions of possible food flavors. But taste is only one component of flavor recognition; flavors also are recognizable by aroma, color, texture, and heat. Taste and flavor are not synonymous terms, although people commonly confuse taste with flavor recognition (Soter et al., 2008).

Four Types of Taste Papillae

• 1. Fungiform• 2. Foliate• 3. Circumvallate• 4. Filliform

Circumvallate

Fungiform

FoliateFoliate

Fungiform

• Highest in concentration• Densely populated at the tip of the tongue• Also scattered across whole tongue• Innervated by Facial Nerve

Foliate

• Located on the side of the tongue• Appear like short vertical folds• Innervated by Facial and Glossopharyngeal

Cranial Nerves

Circumvallate• There are only about 10 to 14 of these papillae on most people, and they

are present at the back of the oral part of the tongue. • They are arranged in a circular-shaped row just in front of the sulcus

terminalis of the tongue. • They are associated with ducts of Von Ebner's glands, and are innervated

by the glossopharyngeal nerve

Filiform

• small prominences on the surface of the tongue. • Thin, long "V"-shaped cones that don't contain taste buds but are the

most numerous, covering most of the dorsum (upper surface).• Mechanical and not involved in gustation.• Tactile sensors, recognize;

– Heat– Texture– Pungency

Anatomy of Taste

• Taste receptors– Back of the throat– Upper one third of the esophagus– Most are located on the tongue

– Anterior portion of tongue is covered with dome shaped projections called papillae• Taste receptor cells are found inside • Four types of papillae

• The sides of each type of cell contains the taste buds.

• They act like nerve cells without the axons.• When you taste food, it enters the taste cell

and causes the charges within the cell to change from negative to positive, this carries the signal to the brain.

Physiology of Taste

• Some taste goes directly into the cell, while others need a mediator.

• Taste stimuli that are electrolytes can enter the taste cells directly. The taste stimulus sodium enters the taste receptor cell and, once enough positive charge accumulates, depolarization occurs to transmit the taste sensation of salty (Smith & Margolskee, 2001).

• Calcium channels then are opened and the taste cell repolarizes. Citric acid, which is perceived in the brain as sour, disassociates in solution into hydrogen ions. Those hydrogen ions enter the taste cell directly, block potassium ion channels, and open other ion channels at the same time to cause depolarization inside of the taste cell and the transmission of sour taste (Smith & Margolskee, 2001).

• Quinine and sucrose are not electrolytes; they need mediators to enter the cell and induce the action potential. Sucrose attaches to G-protein–coupled receptor cells to enter the taste cell and mediates potassium channel closure, which results in the accumulation of a positive charge within the cell to transmit sweet taste (Smith & Margolskee, 2001).

Nerves of Taste

• Cranial Nerves– VII (Facial nerve), anterior tongue– IX (Glossopharyngeal) posterior tongue– X (Vagus) back of throat, upper esophagus– I (Olfactory) is for smell

Taste and smell are often confused.

Pathophysiology of Taste

• 4 different taste dysfunctions– 1. Dysgeusia-Persistent metallic or bitter taste

– 2. HypoGeusia-partial loss of taste, one or more of sweet, salty, and bitter.

– 3. Ageusia-complete loss of taste

– 4. Xerostomia- dry mouth

• Taste cells have a unique physiologic feature. If the nerve supply to a taste cell is severed, it will die. That finding is important because treatments outside the mouth can cause taste dysfunction by both interrupting the sensation signal to the brain and by directly affecting the number of taste receptor cells (Just et al., 2005).

Xerostomia

• Two types of Salivary Glands– Submandibular and Parotid

• Submandibular-keeps the mouth moist and humidifies the inspired air by secreting saliva at a constant rate of about 0.3ml/min (Berk, Shivnani, & Small, 2005).• Parotid-Saliva flow is dependent on CNS stimulation.

(Berk, et al, 2005).

3 Reasons Dry mouth affects taste

• Taste stimuli have to be in liquid for to reach the taste receptors

• Thick saliva is more highly concentrated in salt than thin saliva (Granot & Naglor, 2005). Salt is known to affect sweet, bitter and sour tastes (Neta, et al, 2009).

• Dry mouths are more acidic (Chambers, et al, (2004).– Lower the pH the sweeter tastes and higher the pH less

sweet the taste. (Abe, 2008; Neta, et al, 2009).

Regional Neuropathy

• Because taste buds cannot produce numbness they produce phantom taste sensations (Granot & Naglar, 2005).

• Burning mouth pain may also be a trigeminal nerve reaction to taste stimulation.

• Leads to pain with eating, can be why some prefer soft bland foods.

Cancer Treatments/ Side Effects

• Surgery- directly causes severed nerves.• Radiation-causes de-epithelialization of the

taste receptor cells.• Chemotherapy-systemic therapy attacking

rapidly dividing cells (alimentary canal).

Weight loss

• Inability to taste can lead to decreased appetite, early satiety, food aversions.

• Taste identifies whether or not food is safe to eat.

Sensory Deprivation

• Loss of taste can be distressing. (Sherry, 2001)• Loss of comfort that comes with eating. Taste

centers in the brain that deal with the pleasantness with eating are close to the areas that deal with emotions. (Rolls, 2005; Scott, 2005).

• Taste dysfunction is associated with decreased food consumption, poor appetite, early satiety, altered nutrition, and impaired social interactions (Abe, 2008; Boyce & Shone, 2006; Hutton, Baracos, & Wismer, 2007).

Nursing Implications

• Education before, during and after treatment.• Understand the dysfunctions.• Frequent assessments.

Dysguesia

• Do you have a bitter or metallic taste in your mouth since you were diagnosed with cancer? Encourage smooth, blended foods.

• Discourage spicy foods and foods with rough texture. Dysgeusia is a problem of food texture and heat sensation.

• Does eating cause you to experience pain?• Avoid temperature extremes and experiment with food

temperatures. Temperature sensitivity is individualized, so cold or warm may hurt or feel soothing.

Hypogeusia

• Does food taste as good to you since your cancer diagnosis?

• Chew food well and take fluid in the mouth with each bite. Food has to be in a solution form to get down into the taste buds so it can be tasted.

• Does food taste different since your cancer diagnosis?• Experiment with seasoning, particularly salt and

aromatic herbs. Salt helps adjust sour and sweet tastes. Sweet helps adjust bitter. Aromatic herbs enhance flavor recognition.

Ageusia

• Is there a specific taste, including sweet, sour, salty, or bitter, that you cannot taste at all?

• Encourage attractively presented food and use of aromatic herbs to appeal to the other senses. Patients who lose the ability to taste one whole modality have the greatest difficulty with appetite changes. Encourage family members who prepare food to make it visually appealing.

• Do you find that food texture is more important to you now than before cancer?

• Encourage foods that are smooth and creamy. Smooth and creamy sensations stimulate the pleasure centers in the brain so that eating feels enjoyable.

• Do you sometimes find you forget to eat?• Set aside specific meal times and make the eating environment pleasant.

When taste is decreased, appetite often is decreased. Eating at set times helps prevent forgetting to eat.

Xerostomia

• Visually inspect oral mucosa for dryness and cracking. Chew food thoroughly and take more liquids. Food needs to be in solution to get down into the taste bud.

• Do you have a dry mouth or thick saliva? • Try using less salt than usual.

References• Abe, K. (2008). Studies on taste: Molecular biology and food science. Bioscience, Biotechnology, and Biochemistry,

72, 1647–1656. doi:10.1271/bbb.70690• Bartoshuk, L. (1989). Clinical evaluation of the sense of taste. Ear, Nose, and Throat Journal, 68, 331–337.• Berk, L.B., Shivnani, A.T., & Small, W., Jr. (2005). Pathophysiology and management of radiation-induced

xerostomia. Journal of Supportive Oncology, 3, 191–200.• Blonde, G.D., Garcea, M., & Spector, A.C. (2006). The relative effects of transection of the gustatory branches of the

seventh and ninth cranial nerves on NaCl taste detection in rats. Behavioral Neuroscience, 120, 580–589. doi:10.1037/0735-7044.120.3.580

• Boyce, J.M., & Shone, G.R. (2006). Effects of ageing on smell and taste. Postgraduate Medical Journal, 82, 239–241. doi:10.1136/pgmi.2005.039453

• Breslin, P.A., & Huang, L. (2006). Human taste: Peripheral anatomy, taste transduction, and coding. Advances in Oto-Rhino-Laryngology, 63, 152–190.

• Chambers, M.S., Garden, A.S., Kies, M.S., & Martin, J.W. (2004). Radiation-induced xerostomia in patients with head and neck cancer: Pathogenesis, impact on quality of life, and management. Head and Neck, 26, 796–807. doi:10.1002.hed.20045

• DeSimone, J.A., & Lyall, V. (2006). Taste receptors in the gastrointestinal tract III. Salty and sour taste: Sensing of sodium and protons by the tongue. American Journal of Physiology. Gastrointestinal and Liver Physiology, 291, G1005–G1010. doi:10.1152/ajpgi.00235.2006

• Femiano, F., Scully, C., & Gombos, F. (2002). Idiopathic dysgeusia: An open trial of alpha lipoic acid (ALA) therapy. International Journal of Oral and Maxillofacial Surgery, 31, 625–628. doi:10.1054/ijom.2002.0276

• Granot, M., & Nagler, R.M. (2005). Association between regional idiopathic neuropathy and salivary involvement as the possible mechanism for oral sensory complaints. Journal of Pain, 6, 581–587.

• Haddad, R., Sonis, S., Posner, M., Wirth, L., Costello, R., Braschayko, P., . . . Tishler, R.B. (2009). Randomized phase 2 study of concomitant chemoradiotherapy using weekly carboplatin/paclitaxel with or without daily subcutaneous amifostine in patients with locally advanced head and neck cancer. Cancer, 115, 4514–4523. doi:10.1002/cncr.24525

• Henkin, R.I., & Velicu, I. (2008). cAMP and cGMP in nasal mucus: Relationships to taste and smell dysfunction, gender, and age. Clinical and Investigative Medicine, 31, E71–E77.

• Hoffman, H.J., Ishii, E.K., & MacTurk, R.H. (1998). Age-related changes in the prevalence of smell/taste problems among the United States adult population. Results of the 1994 disability supplement to the National Health Interview Survey (NHIS). Annals of the New York Academy of Sciences, 855, 716–722.

• Hutton, J.L., Baracos, V.E., & Wismer, W.V. (2007). Chemosensory dysfunction is a primary factor in the evolution of declining nutritional status and quality of life in patients with advanced cancer. Journal of Pain and Symptom Management, 33, 156–165. doi:10.1016/j.jpainsymman.2006.07.017

• Just, T., Pau, H.W., Bombor, I., Guthoff, R.F., Fietkau, R., & Hummel, T. (2005). Confocal microscopy of the peripheral gustatory system: Comparison between healthy subjects and patients suffering from taste disorders during radiochemotherapy. Laryngoscope, 115, 2178–2182.

• Larsson, M., Hedelin, B., & Athlin, E. (2003). Lived experiences of eating problems for patients with head and neck cancer during radiotherapy. Journal of Clinical Nursing, 12, 562–570.

• Laviano, A., Inui, A., Meguid, M.M., Molfino, A., Conte, C., & Rossi Fanelli, F. (2008). NPY and brain monoamines in the pathogenesis of cancer anorexia. Nutrition, 24, 802–805.

• Lundy, R.F., Jr. (2008). Gustatory hedonic value: Potential function for forebrain control of brainstem taste processing. Neuroscience and Biobehavioral Reviews, 32, 1601–1606.

• Mirza, N., Machtay, M., Devine, P.A., Troxel, A., Abboud, S.K., & Doty, R.L. (2008). Gustatory impairment in patients undergoing head and neck irradiation. Laryngoscope, 118, 24–31.

• Neta, E.R., Johanningsmeier, S.D., Drake, M.A., & McFeeters, R.F. (2009). Effects of pH adjustment and sodium ions on sour taste intensity of organic acids. Journal of Food Science, 74, S165–S169.

• Pribitkin, E., Rosenthal, M.D., & Cowart, B.J. (2003). Prevalence and causes of severe taste loss in a chemosensory clinic population. Annals of Otology, Rhinology, and Laryngology, 112, 971–978.

• TABLE 3. Common Myths About Taste• MythFact• Taste is tongue-site specific.All taste buds are capable of sensing all taste modalities, regardless of their

location on the tongue.• If olfactory function is impaired, then taste will be too. Smell and taste are separate sensory processes,

but both are involved with flavor recognition.• Using plastic utensils will help patients with dysgeusia. Dysgeusia, or a bitter or metallic taste, is a clinical

manifestation of regional neuropathy, not an excessive ability to taste bitter or metal.• Sucking on hard candy will help manage taste changes. Although sour foods do stimulate saliva flow, which

aids normal taste function, the intervention is only appropriate for patients who have enough saliva to dissolve hard sour candies. Saliva substitutes or rinsing the mouth and drinking more fluid work better.

• Eating cold foods helps with taste dysfunction. Eating cold foods helps decrease nausea associated with food aroma, but for people with impaired taste, eating warm aromatic foods enhances flavor recognition.

• Use more salt to help with taste dysfunction. Salt adjustment is sometimes helpful, but patients with thick saliva may need less salt because thick saliva is more highly concentrated in sodium chloride than in thin saliva.