The principal objective of this paper is to demonstrate the role of taste and flavor in health from the ancient science of Ayurveda to modern medicine; specifically their mechanisms and roles in space medicine and their clinical relevance in modern heath care. It also describes the brief history of the use of the monosodium glutamate or flavor enhancers ("Umami substance") that improve the quality of food intake by stimulating chemosensory perception. In addition, the dietary nucleotides are known to be the components of "Umami substance" and the benefit of their use has been proposed in various types of patients with cancer, radiation therapy, organ transplantation, and for application in space medicine.