# Taste disorders and their causes

Questions related to gustation and olfaction.

### Problem

Individuals heavily rely on their gustatory sense (taste) in everyday life. Taste is evolutionarily important in humans, since the ability to detect bitter compounds (which normally indicate a poisonous or toxic substance) is beneficial to survival, as is the ability to detect sweet compounds (indicating presence of sugar, an important source of energy). When a person’s sense of taste becomes impaired they are more likely to experience quality of life issues, and can also be more susceptible to serious issues related to dietary intake, like diabetes and heart disease. There are varying levels of taste impairment - hypogeusia, or partial loss of taste, is the reduced ability to detect sweet, sour, bitter, salty, or umami molecules. Ageusia is much more rare than hypogeusia, and is the total loss of taste detection. Dysgeusia is the distortion of flavors on the tongue, and can involve unpleasant or metallic taste. Taste disorders are usually caused by some type of injury or illness, but can sometimes be present at birth.
A researcher is interested in finding out more about taste disorders and their causes. He studies the patient records of 1500 adults who have been diagnosed with a taste disorder in the past two years, and is able to link the disorders to six broad causes. Table 1 outlines the percentage of taste disorders linked to each cause.
Cause of taste disorderPercent of patients