Chemotherapy, nutrition and metallic flavors

Sep 19 2006

About two million cancer patients currently receiving certain drug therapies and chemotherapy find foods and beverages to have a foul metallic flavor, according to a medical study. In general, more than 40 percent of hospitalized patients suffer from malnutrition due to taste and smell dysfunction.

"Unfortunately, these problems that impact nutrition and quality of life are underestimated and understudied by oncologists," said Andrea Dietrich, Virginia Tech professor of civil and environmental engineering (CEE).

Dietrich believes there are two components to the metallic flavor -- the taste of metal ions on the tongue and the production of metal-catalyzed odors in the mouth that create a retro-nasal effect. "I am attempting to gain a better understanding of the metallic sensation, its prevention, and application to human health," Dietrich said.

Along with two of her university colleagues, Susan E. Duncan, professor of food science and technology, and YongWoo Lee, an assistant professor in the biomedical sciences and pathology department and a member of the Virginia Tech-Wake Forest University School of Biomedical Engineering and Sciences, Dietrich is the recipient of a $200,000 grant from the Institute of Public Health and Water Research (IPWR) to examine the problems of foul flavored water. The interdisciplinary investigative team combines proficiency in food oxidation and off-flavors, water chemistry, cell biology, and human perception.

Dietrich, the principal investigator on the project, is an expert on water quality and treatment, as well as its taste and odor assessment. In fact there are some 33 identified flavors of drinking water acknowledged by the American Water Works Association and Research Foundation (AwwaRF). They range in description from "wet paper" to "crushed grass" to "peaty" to "plastic."

Several years ago, AwwaRF sponsored Dietrich to travel around the U.S. to educate utility staff and managers on how to use sensory analysis to detect changes in water quality. She is also a co-developer of three odor-testing methods for the daily monitoring of raw and untreated water.

Now she is hoping to work with medical personnel as she, Duncan, and Lee compare the sensory thresholds, recommended nutritional levels, and adverse health effect levels of iron and copper in water, and their relationship to health-based problems such as persistent metallic tastes of patients receiving chemotherapy.

They hope to identify the cause of the metallic flavor in the mouth when drinking water contains metal ions, specifically iron and copper. Their research will also evaluate the use of antioxidants to prevent the metallic flavor production. "If we can discover the cause of the production of metallic flavor, then preventive methods can be taken accordingly," Dietrich said.

In correct amounts, metals in drinking water are actually important sources of micronutrients in the human diet. In fact, iron and copper are commonly found in drinking water, and they can be an important source of these mircronutrients. However, there are thresholds. If ingested at higher concentrations, greater than three milligrams per liter, iron and copper "may cause nausea, vomiting, diarrhea, kidney and liver damage," Dietrich explained.

Some tests will be done with human volunteers to determine reactions of volatile compounds in the mouth. Since saliva contains proteins and enzymes, it may have some effect in enhancing the metallic flavor. They will also use in-vitro experiments in order to conduct experiments at higher concentrations without endangering anyone, Dietrich added.

Perception of taste and odor is very complex, and like nutritional needs, varies depending on age, gender, race, health status, prior exposure and experience.

Two graduate CEE students, Pinar Omur-Ozbek and Jose Cerrato, both of Blacksburg, Va., will work on this project.