Why It Is Necessary to Measure All Taste Qualities to Evaluate Taste Function in Normal Subjects and In Patients with Taste Loss (Hypoguesia)
There are at least four basic taste qualities — salt, sweet, sour and bitter. There may be others but these four are the major taste qualities reflective of normal function.
We have defined specific activities of each taste quality in receptors on the tongue, palate and pharynx of human subjects (1). Normal subjects respond to each taste quality and measurement of each stimulus with quantifiable responses. Indeed, in order to determine normal taste function it is necessary to measure all of these qualities — measurement of one, two or even just three taste qualities is insufficient to assess human taste function.
Not only is it necessary to measure all taste qualities it is necessary to quantitate each taste quality with respect to normal taste function. We can do this by measurements of taste detection thresholds, taste recognition thresholds, magnitude estimation and hedonics for each taste quality (2). This battery of tests is necessary to determine normal taste function. If any quantitative measurement is less sensitive than that of normal subjects even in one taste quality then the patient has hypogeusia, an abnormality of taste function. These results initiate an evaluation of the cause of hypogeusia such that each aspect of this system can be evaluated — the brain, the nerves and the receptors which comprise this complex system. These results indicate why it is important to measure responses to each taste quality to determine normal or abnormal taste function.