Changes in taste during cancer treatment

Some studies conducted with different patients undergoing cancer treatment have found that the therapies used can significantly affect the receptors of the senses of smell and taste, altering or even destroying them (COHEN et al., 2014; SANCHEZ-LARA et al., 2010).

The first reports of patients with changes in their sense of taste are loss of sensitivity to tastes (dysgeusia), especially to sweets, sensations of bitterness and metal in the mouth, more noticeable in cases of chemotherapy treatment due to the medication itself, and dry mouth (xerostomia) (EPSTEIN & BARASCH). These factors cause patients to have difficulty consuming food or even consume more caloric foods, and, as a consequence, there are nutritional changes and significant impacts on quality of life. Another implication that can influence taste is the length of time patients are subjected to enteral* and parenteral** nutrition.

To assess umami taste sensitivity, two studies were conducted with head and neck cancer patients undergoing radiation therapy. Shi et al. (2004) conducted a study with 30 patients, measuring thresholds (sensitivity thresholds) to basic tastes during different radiation cycles. The results showed that umami sensitivity was more pronounced than the other four.

Yamashita et al. (2009) evaluated 52 patients who underwent radiation for 9 weeks of treatment and found that the patients had umami taste sensitivity until the third week of treatment. After this period, a decline occurred, with a slight improvement in sensitivity after the eighth week. Sensitivity was suggested to exist, but it is limited due to the duration and intensity of the treatments, a fact that differentiated this study from the study by Shi et al. (2004), which did not assess treatment duration.

In Brazil, a study was conducted at the School of Public Health of the University of São Paulo (USP) (GRINGERG-ELMAN & PINTO E SILVA, 2011). The researchers tested umami taste sensitivity in children with ALL (Acute Lymphoblastic Leukemia) and NHL (Non-Hodgkin’s Lymphoma) using solutions with different concentrations of the flavor enhancer MSG and foods containing it. A total of 102 patients between the ages of 6 and 15 were evaluated. Most patients detected the umami taste from the second concentration of the solutions offered in the test, in both sessions. This demonstrated that children are sensitive to this taste, and that the use of glutamate at the recommended technological concentrations (<1%) in different preparations and appropriate dietary guidance could help improve the nutritional status of children undergoing treatment for these types of cancer.

Studies conducted in Japan have shown that hospitalized elderly individuals, who also have taste alterations and xerostomia, significantly increased salivation when stimulated with monosodium glutamate solutions compared to citric acid solutions (HAYAKAWA et al., 2007; HAYAKAWA et al., 2008; UNEYAMA et al., 2009). Increased salivation led to better eating habits and improved nutritional status (TOMOE et al., 2009). This strategy could also be used in cancer patients to reduce dry mouth, but there is currently no research reporting increased salivation in this population.

Further studies are needed to assess sensitivity to the fifth taste, as well as increased salivation and acceptance of umami-rich foods in children and adults with different types of cancer. From the few studies that have been published, it can be seen that a diverse menu, as well as the constant stimulation of taste sensations, can help patients maintain their sense of taste, as this is extremely important for improving nutritional status and quality of life during and after treatment.

* Enteral nutrition: nutritional therapy or supplementary diet administered through the mouth, nasal tube, or ostomy (surgery that involves opening a hollow organ to introduce food or drain feces and urine).

** Parenteral nutrition: administration of nutrients through the intravenous route.