Japanese dietary intake of salt and protein--relating to the strategy of salt restriction.

The high level of Japanese salt intake, which has been the major risk factor for cerebrovascular disease and hypertension, has decreased since World War II, and reached a steady level. In the present study, the dietary salt intake in Tohoku (once the district of highest sodium intake) and that in Kyushu (once the district of median or low sodium intake) were studied in relation to nutritional status by the analysis of sodium and urea-nitrogen excretion in 24-hr urine samples collected from 305 healthy Japanese. When the amount of urinary creatinine and urea-nitrogen were adjusted, the mean value of urinary sodium in females was significantly larger in Tohoku than in Kyushu, but not significantly in males. The regional difference of salt intake still remains, although it seems to be disappearing. Traditionally, Japanese high intake of salt was accompanied by poor nutritional status. In the present study, however, a significant positive correlation was observed between sodium and urea-nitrogen. The excess of protein intake would cause the excess of salt intake. Therefore, the strategy of further salt restriction should be directed to not only traditional salty foods but also nutritional status such as protein intake.