Hisayuki Uneyama, Akira Uematsu, Ken Iwatsuki and Eiji Nakamura
About a century ago, a new tastant, umami taste substance (L-glutamate) was discovered in Japan with a motivation to improve the poor nutritional status of Japanese people by supplying affordable delicious flavors. Since then, Japanese physiologists have been leading the taste research to establish the taste of free L-glutamate as the fifth basic taste (umami taste), in addition to sweet, bitter, sour and salty taste. Taste physiologsts have presented the hypothesis that the umami taste is a sensory marker for protein intake, like as salty taste is that for mineral intake. Evidence has now accumulated that free glutamate is sensed by taste receptors on the tongue as well as in the gastrointestinal tract, leading to protein digestion and absorption, as well as perceived palatability and appetite. Analytical food technology has revealed that a high level of free glutamate is contained in seasonings used worldwide, including soy, fish and oyster sauces, and tomato ketchup, or food stuffs such as tomato and cheese. We are dedicated to bringing the nutritional and physiological benefits of glutamate for human health through incorporation of umami taste to worldwide food culture. In this review, we will introduce our recent findings about the nutritional and physiological significance of the umami taste in protein intake and utilization.