A group of Duke University researchers has been examining the complex relationship that involves appetite, taste, smell, weight loss, nutritional deficits, and the effects of all these factors on the immune system.
It's an important issue: Cancer patients who lose weight typically develop serious nutritional problems that compromise their immunity and chances for long-term survival, says study author Jennifer Garst, MD, assistant professor of oncology at Duke Comprehensive Cancer Center in Durham, N.C.
Garst and colleagues presented their findings at the annual Association of Chemoreception Sciences. Their study is funded by the National Institute on Aging.
"Weight loss has long been a hallmark of cancer, but it has been considered an inevitable byproduct of the disease process and chemotherapy drugs," says co-author Susan Schiffman, PhD, in a news release.
However, weight loss has never been considered a treatable symptom that can affect a patient's outcome, says Schiffman. "If we can show that taste and smell deficits are responsible for the weight loss in a specific population of patients, then we can intervene and potentially improve patient outcomes."
In their studies, the Duke team has linked taste and smell deficits with reduced levels of key immune system cells, like T-cells and B-cells. Even among patients who are eating the same number of calories, those with taste and smell problems often avoid foods with high nutritional value, such as fresh fruits and vegetables -- further depressing the immune system, Schiffman says.
However, Duke studies have also shown that flavor-enhancing powders -- derived from actual foods such as cheese, bacon, garlic, and fruits -- can improve a patient's appetite, leading to significantly higher levels of B-cells and T-cells.
In their current study, the Duke group looked specifically at the issue of taste and smell deficits. They also investigated the use of these flavor powders to make food more appealing to patients.
In their study of 33 lung cancer patients undergoing chemotherapy, the Duke researchers tested patients' ability to detect and recognize odors and flavors presented to them in the laboratory. Patients who reported the lowest degree of taste and smell ability -- and who had lowest T-cell and B-cell levels -- also had the most weight loss, body mass loss, and nutritional deficits.
The second part of their study has not yet been completed. In it, researchers are giving half the patients powdered flavor enhancers in their foods. The other patients are receiving no enhancers. All the patients have received advice as to what foods relieve dry mouth, constipation, diarrhea, and other side effects of treatments.
Researchers expect that patients who receive flavor-enhanced food will lose less weight and have a higher immune status at their eight-month checkup.
There are various theories why people lose their appetite and sense of taste, says Garst. Chemotherapy drugs are known to alter taste and smell by blunting the normal turnover rate of taste and smell receptors on the tongue and in the nasal passages. Radiation treatments can damage taste and smell receptors, giving food a metallic flavor. Some tumors can even secrete a protein that suppresses the appetite.
By looking at this aspect of cancer treatment, researchers expect to improve both patients' survival rate and their quality of life, she says.