Taste and Health: New Frontiers in Oral Physiology and Rehabilitation Physiological Significance of Taste on Ingestion and Swallowing

Due to an increasing incidence of stroke as well as a growing population of elderly individuals, the number of bedridden persons in Japan is increasing. Since their muscle and nervous system for oral functions may be lowered, many of them are suffered with difficulty in swallowing (dysphasia). In cases of severe swallowing disorders, patients may aspirate their food, in which bacteria carried with the food into the airway might cause a critical condition such as pneumonia. Tube feeding is one way to bypass the pharynx, and avoid the aspiration of food. However, tube feeding deprives patients of the pleasure associated with eating. Most patients want to take food through the mouth; thus methods need to be developed that address difficulties in swallowing. Mastication have been understood being a process to crash and mix with saliva for safe swallow; however, in addition to it humans sense the physical and chemical (i.e., taste) properties of food during mastication so that we secure security of the appetite. Swallowing is a reflex during which many muscles are activated in given timings to move food and/or liquid from the oral cavity to the stomach. Since affection system may strongly interpose in the swallowing process, a good appetite may be the most important factor for a smooth swallowing process. Properties required for the food include: clear taste, proper temperature, uniformity, agglutination, and moisture.