Zinc for Taste Abnormalities in Cancer Patients
Abstract & Commentary
Synopsis: This pharmacologic therapy is effective and well tolerated; it could become a routine in clinical practice to improve the supportive care of patients with taste alterations resulting from head and neck cancer.
Source: Ripamonti C, et al. Cancer 1998;82:1938-1945.
In uncontrolled clinical trials, the administration of oral zinc sulfate has been reported both to prevent and correct taste abnormalities in cancer patients receiving external radiotherapy (ERT) to the head and neck region.
Eighteen patients (14 male, mean age 57) were randomized to receive either elemental zinc sulfate tablets (a dose of 45 mg) or placebo tablets three times a day at the onset of subjective perception of taste alterations during the course of ERT and up to one month after ERT termination. Taste acuity was determined by measuring detection and recognition thresholds for four taste qualities. Intolerance of zinc sulfate or placebo administration was investigated, and the oral cavity was examined. All the evaluations were studied prior to, at weekly intervals during, and one month after ERT administration.
Taste acuity for one or more taste qualities was already impaired before ERT. During ERT, taste alterations were experienced at least once for a minimum of three of the eight measured thresholds by all nine of the patients, and three of the nine patients became aware of some alteration within the first week. The patients treated with placebo experienced a greater worsening of taste acuity during ERT compared with those treated with zinc sulfate. One month after ERT, the patients receiving zinc sulfate had a quicker recovery of taste acuity than those receiving placebo.
After ERT termination, statistically significant differences between the two groups emerged for urea (bitter) detection, and sodium chloride (salt), saccharose (sweet), and hydrogen chloride (sour) recognition thresholds.
This pharmacologic therapy is effective and well tolerated; it could become a routine in clinical practice to improve the supportive care of patients with taste alterations resulting from head and neck cancer.
COMMENT by John La Puma, MD, FACP
Taste is a funny thing. For one, it’s incredibly individual. Taste buds tell us salty, sweet, sour, bitter, and maybe savory. Some of us have 11 taste buds per centimeter squared of tongue and some of us have 1100. And the number of buds doesn’t even correlate with how good something tastes.
Most taste disorders—hypogeusia (less), ageusia (none), and dysgeusia (distorted)—are not at the top of the medical record problem list. Many physicians think of them as an early, usually reversible, complication of cancer and of chemo and radiotherapy. If only there were something that could give flavor back to people denied this basic sensual pleasure.
Maybe zinc. Ripamonti and colleagues, at the National Cancer Institute of Milan, found zinc blood levels and subjects’ taste acuity to be low prior to ERT. Ripamonti et al started zinc and placebo when subjects reported "the moment of subjective worsening of taste acuity."
No side effects or dropouts were reported. There were significant differences, as above, in the nine zinc patients.
No one knows why zinc may work. Zinc is an essential element that has a role in a number of metalloenzymes, including alkaline phosphatase, which is the "most abundant enzyme isolated from the taste bud membrane."
If zinc does work, it may have a steep price. Too much zinc in HIV-positive patients probably reduces immunity. Barrette writes ". . . cohort studies [of HIV-positive patients] suggest that increasing dietary intake of zinc or use of any zinc supplement increases the risk of disease progression." Barrette discourages the use of zinc supplements in these patients, other than in a multivitamin, until further studies prove their safety.
To all of your immuno- and taste-compromised patients, recommend other types of flavor not dependent on taste buds—the heat of chilies and the bubbles of seltzer, for example, both taste good because they jangle the VIIth cranial nerve. With HIV-negative patients who desperately want to try to recover the flavor of their food, discuss a single, time-limited, two- to four-week trial of zinc sulfate. HIV-positive patients should not take supplemental zinc. (Dr. La Puma is Adjunct Professor of Nutrition, Kendall College, Director, C.H.E.F. Clinic, C.H.E.F. Skills Research, Alexian Brothers Medical Center, Elk Grove Village, IL.)
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