Assessment of Umami Taste Sensitivity

Patients with gustatory disorders often complain of persistent impairment of umami taste, a synonym for savory or broth-like flavor, even after the recovery of the other four basic taste sensations (sweet, salty, sour, and bitter). Umami taste is important for maintaining not only the quality of life but also good health, and therefore, it seems important to assess and treat the impairment of umami taste perception. At present, however, there is no clinical test for umami taste, even though tests for the other four basic tastes have been widely used in quantitative gustometry. We have developed a new method to clinically assess the sensitivity of umami taste using a filter paper disc (FPD) with monosodium glutamate (MSG) as the prototype umami substance. We found that some elderly patients complained only of the loss of umami taste sensation, whereas the sensation of the other four basic tastes (sweet, salty, sour, and bitter) was normal. Those patients without normal umami taste sensitivity were all over 65 years old, and complained of appetite and weight loss, resulting in poor general health. After treatment, their umami taste threshold recovered, and they regained appetite and weight. In this article, we review our and related studies concerning umami taste.