Taste alteration refers to a decrease in the ability to taste foods (hypogeusia), changes in how food tastes (dysgeusia), or the complete loss of the ability to taste foods (ageusia). It also refers to the presence of a metallic or medicine-like taste in the mouth. Taste alterations may occur as a result of cancer treatment, infection within the mouth, or the cancer itself.
Taste alteration can have a significant effect on the nutritional status of a cancer patient. Patients with taste alteration may avoid certain foods, lose their appetite (anorexia ), and lose weight. Eating can be a chore when the patient also has a dry mouth (xerostomia ) or a mouth infection, such as thrush .
Humans have the ability to taste bitter, salty, sour, and sweet flavors with the taste buds. Taste buds are on the tongue, back portion of the roof of the mouth (soft palate), and the back of the throat. The taste buds are composed of taste cells. Taste cells have tiny hairs (microvilli) which take up microscopic particles of food in the mouth. Taste alteration occurs when the taste buds are damaged by cancer therapy or as a symptom of xerostomia or infection.
Taste alteration may be caused by the cancer itself. Invasion of the mouth by the tumor can alter taste. Between 88% and 93% of the patients with head and neck tumors have taste alterations. Cancer can cause the patient to become deficient in nutrients such as copper, niacin, nickel, vitamin A, and zinc, which can lead to taste alterations. In addition, it is believed that cancer-related chemicals in the bloodstream may affect taste.
Taste alteration can occur in patients who are receiving radiation therapy to the head, neck, or chest. The taste buds are very sensitive to radiation and taste alteration can occur within the first two weeks of radiation therapy. Also, radiation therapy can cause decreases in the production of saliva, which can alter taste. Reduced amounts of saliva can change the taste of salty and bitter foods.
Patients undergoing chemotherapy may experience taste alterations. Chemotherapy drugs damage the taste cells. The resulting alterations in taste are varied but the most common complaints include: a metallic taste, enhanced taste of bitter flavors (such as beef, pork, coffee, chocolate), and reduced taste of sweet flavors. Between 36% and 71% of the patients undergoing chemotherapy experience taste changes. Antibiotics , pain relievers (analgesics), antidepressants, and many other drugs can also affect taste. Chemotherapy drugs that are frequently associated with taste changes include:
- nitrogen mustard
Surgery to the head or neck can also cause taste alteration. Metallic or medicine-like tastes can be caused by a zinc deficiency or by increased levels of calcium or lactate.
Taste alteration is usually a temporary condition, although it may take a few months for taste to return to normal. However, surgery of the roof of the mouth (hard palate), tongue, or throat or high-dose radiation therapy can cause permanent taste alteration.
There is no cure or treatment for taste alteration. Patients with this condition are counseled on methods to overcome the affect of taste alteration on eating. However, some studies have shown that zinc supplements, given at the first sign of taste alteration, can reduce radiation-induced taste changes.
The patient's teeth should be brushed and flossed before eating to remove old tastes and refresh the mouth. Rinsing the mouth with salted water, water containing baking soda, tea, or ginger ale before eating may be helpful. Brushing and flossing should be performed carefully to prevent damage to the weakened mouth tissues.
There are a variety of measures that can be taken to make food more tasteful and less offensive. Dietary recommendations include:
- eating foods that are cool or at room temperature
- adding tart flavors to foods such as lemon, citrus, and vinegar, unless mouth sores are present
- using mints, gum, or lemon drops to remove bad tastes after eating
- adding more sugar to foods to reduce salty, acid, or bitter tastes
- using barbecue sauce, basil, catsup, chili powder, garlic, mint, mustard, onion, oregano, rosemary, or tarragon to add flavor to foods
- eating frozen fruits such as grapes, melons, or oranges
- eating fresh vegetables, which may taste better than frozen or canned ones
Alternative and complementary therapies
Taste alteration related to a zinc deficiency can be treated by the addition of zinc to the diet. Zinc deficiency can be relieved by taking zinc picolinate supplements. Foods that are rich sources of zinc include oysters, crab, beef, pork, eggs, nuts, yogurt, and whole grains.
See Also Sjögren's syndrome
Belinda Rowland, Ph.D.
—The complete loss of the ability to taste foods.
—Changes in what food normally tastes like.
—The decreased ability to taste foods.
—Tiny bumps located in several parts of the mouth that enable one to taste foods.
—The cells that make up taste buds.