The relationship between the so-called "essential hypertension" and metabolism of salt and water has called the world-wide attention. Also it has been proved that mortality from apoplexy and the level of blood pressure in Japan are parallel with the salt intake of the inhabitants. In such subject, it is naturally necessary to investigate factors which are considered to give influences to sodium metabolism. For instance, aldosterone, a hormone which has relation to the metabolism of salt and water, and other minerals have to be investigated.

We have been greatly interested in　the fact that the mortality from apoplexy differes greatly between Akita and Aomori Prefectures which are neighboring each other, and made　investigations on the relation with apple which are raised greatly (70% of the total production of this country) in Aomori Prefecture especially around the Hirosaki area where our university is located. It is also interesting that the mortality is lower at the apple producing zone than the rice producing zone even in the same Nakatsugaru area of Aomori Prefecture. The large difference in the living conditions of the inhabitants between these 2 prefectures is related with apple raising. Naturally, the inhabitants of Aomori Prefecture eat much apples than those of Akita Prefecture do. Blood pressure of Aomori inhabitants is lower than that of Akita inhabitants.

For the　purpose to make a comparative investigation on the balance between Na and K in the dietary life among various regions in Japan,　the urine of the inhabitants of following four regions was　collected successively for three days, and Na and K in it were estimated by flame photometer: A.20 inhabitants of Oinomori, Hirosaki City, Aomori Prefecture (apple-rice field zone), B.20 inhabitants of Kanaya, Onoe Town, Aomori Prefecture (rice- and wheat field zone), C.30 inhabitants of Kamosaki, Sanyo Town, Okayama Prefecture (rice and wheat field zone), and D.32 inhabitants of Ota, Takanosu Town, Akita Prefecture (rice-field zone). The results were shown in the following table, and significant correlation was noted between blood pressure and Na/K ratio in urine(+0.9758, 0.05>p>0.02),

　　　　　　　　　　　　　　　　　　　　　　　　 A　　　B　　 C　　　D

Systolic Blood pressure(mmHg)　　 131.4 129.3 149.7 152.5

Diastolic Blood pressure (mmHg)　　78.6　80.9　85.9　86.6

Na/K ratio in urine　　　　　　　　　　　 5.78　6.74　7.42　7.62

Investigations were made on the relation with K, a factor to give influence to the relation between high blood pressure and the salt intake. The fact that the mortality from apoplexy and high blood pressure was comparatively low in the apple zone of Aomori Prefecture through it was also in the north-eastern district to do with this phenomenon, and author thought the necessity to give consideration to balance bertween Na and K in the daily life.

It is likely that a great portion of the daily salt intake of Japanese comes from the salt in "Miso", which is usually used as "Miso-soup". The present survey was made in order to order to compare the salt concentration in "Miso-soup" and the number of times it is eaten in a day throughout the whole country.

Four representative prefectures were selected from four areas in Japan as follow; Akita prefecture in the Tohoku area, Ibaragi prefecture in the Kanto area, Okayama prefecture in the Chugoku area and Saga prefecture in the Kyusyu area. Elementary schools were classified according to a school scale, and then thirty school were selected　at random　in prefecture. The samples of　"Miso-soup" were selected　from 50 children's homes of each school: 3,758 samples of "Miso-soup" from 88 schools were obtained, their salt concentration　was analysed by means of the Schales and Schales' method.

The following results　were obtained:

1. The salt conｃentration of all samples of "Miso-soup" averaged 1.51%. The mean values in each prefecture were 1.50% in Akita, 1.63% in Ibaragi, 1.44% in Okayama and 1.47% in Saga. The differences was found to be statistically significant among these prefectures.

2. The salt concentration of "Miso-soup" in the inland areas　was higher in general than that in the coastal areas. The salt consentration　of "Miso-soup"　was different both　in the inland areas and in the coastal areas among the four prefectures. The difference between the inland areas and the coastal areas was found in all prefectures except Ibaragi.

3. The salt concentration in "Miso-soup" of farmers was higher than that of non-farmers. The difference was found among the above prefectures, although no difference was found within the same prefecture itself except Ibaragi prefecture.

4. The salt concentration in "Miso-soup" cooked with home-made "Miso" was higher in general than that cooked with "Miso" on the market. The salt conｃentration was different both in the former and the latter was not found　within three prefectures except Ibaragi.

5. There was a remarkable difference in the number of times "Miso-soup" was eaten a day among four prefectures as follows; 2.4 tines in Akita, 2.4 times in Ibaragi, 1.0 times in Okayama and 1.2 times in Saga. It is obvious that farmers eat "Miso-soup" more times than non-farmers in each prefecture, especially in Akita and Ibaragi prefecturtes, and people who use a home-made "Miso" eat "Miso-soup" more times than　people who use ready-made "Miso" bought on the market.