Cancer patients frequently experience dietary difficulties with foods they associate with their disease or its treatment. These patients may suffer from reduced appetite and low food intake, resulting in unintentional weight loss. A number of factors contribute to this, according to sensory scientist Alissa Nolden, PhD, assistant professor of food science at the University of Massachusetts (UMass) Amherst. Alterations in smell and taste perception are often implicated when patients suffer from lack of appetite.

Researchers at UMass Amherst conducted a review and analysis of studies in the literature on changes in taste and smell experienced by cancer patients while undergoing treatment and afterwards to determine the prevalence of these changes in this population. Included studies directly measured the psychophysical response of cancer patients to taste and/or olfactory stimuli and assessed the food behavior of people affected by cancer including their preferences, enjoyment, and dietary intake.1 Although the UMass Amherst team restricted selected studies to those involving adults older than 18, the studies included all types of cancer and treatment.

Their search produced 11 studies published between 1982 and 2018, and comprising 578 participants (380 with cancer and 198 who served as controls). Five studies included patients with more than one type of cancer; patients in the remaining 6 studies had just one type of cancer. The cancer types represented in the studies included breast, colon, esophagogastric, lung, ovarian, prostate, and testicular cancers; lymphoma; and multiple myeloma.

A variety of objective measures were used to gauge smell and taste perception, including detection threshold (the lowest concentration at which a taste stimulus is detected compared with a background such as water) and recognition threshold (the lowest concentration at which a specific taste, such as bitter, is recognized). Taste stimuli were administered to the whole mouth as a rinse or to part of the mouth with a taste strip. Smell studies had used pen-like devices that dispensed odors. Food behavior was evaluated for those studies that included measures of dietary intake by recall, food frequency questionnaires, food weights, or responses to food pictures.

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Treatment-Related Changes

Taste Almost all the studies had measured participants’ changes in taste for sweet, sour, bitter, and salty. Most results demonstrated changes in taste of sweet and that the cancer patients who had a loss of appetite usually preferred food that was less sweet compared with those who had a normal appetite. Other studies showed that changes in taste of bitter were associated with the patients avoiding meat, chocolate, and tea. Some patients had difficulty recognizing sweet and bitter tastes.

Longitudinal studies demonstrated a significant relationship between taste and food behavior. For example, one study described a patient who began having difficulty identifying the taste solutions during the third chemotherapy treatment cycle and consequently consumed less food. In another study, patients became more sensitive to sweet after 2 cycles of chemotherapy and consumed less protein than those who were not sensitive to sweet; and in a third case, a patient had decreased sensitivity to sweet and a reduced appetite before undergoing any treatment.