Salt consumption and nutritional state especially dietary protein level.

To examine the background of excessive salt intake by the people who live in the northeastern district of the mainland of Japan, statistical analysis was carried out on salt consumption with nutritional status with data from the National Nutrition Survey of Japan and prefectural reports. We found that the dietary protein level (using the index animal-protein calorie intake:total calorie intake) was inversely proportional to the salt intake. To clarify the relationship between taste preference and nutritional status, the effects of dietary protein levels on the preference for salt were studied in spontaneously hypertensive rats (SHR), Wistar-Slc rats, and Sprague-Dawley (SD) rats. We found that the appetite or preference for sodium chloride depends not only on a genetic factor but also on the nutritional status, ie, dietary protein levels. We also observed that the preference for the monosodium glutamate solution was not induced in animals fed a low-protein diet. From these observations we speculated that the threshold of taste sensation is increased in rats fed a low-protein diet. To determine the threshold of taste sensation for NaCl, we calculated the turnover time of taste buds, which was lengthened in rats fed a low-protein diet. The findings from statistical analysis and the results from animal experiments suggest that taste preference is influenced not only by genetic factors but also by the nutritional status. Our hypothesis is that dietary protein level is one of the important factors affecting the taste preference for sodium chloride.