The object of this paper is to investigate the efficiency of available Ca contained in the diets used in daily life. At the same time, Mg and P were determined, because it seemed that they had a more direct basis for comparison of Ca-utilization. The following results were obtained.
A great deal of the minerals were recognized in rice bran, sesame seed, cow's milk, dried sardine, soy-bean, carrot leaf, agar-agar and seasoned laver.
The ratios of Ca : P showed more desirable values in vegetables and seaweed than in cereals and animal diets. The extraction ratio of Ca with water showed lower values in rice bran, sesame seed, dried sardine, spinach and leaf-beat. This was probably due to the fact that many contents of fat, or Ca-salts which were hardly dissolved in water were contained in the samples.
An examination was carried out to clarify the availability of Ca in stomach by means of model experiments. The rises of the extraction ratios with 0.1N hydrochloric acid were found in all cases.
In the case of 4 per cent acetic acid, which has many opportunities to be used in the daily cooking, the extraction ratios showed higher levels than those with water and lower levels than those with 0.1 N hydrochloric acid.
Generally, it was recognized that the soluble inorganic-and organic-forms of Ca in animal diets showed higher values than those in vegetable diets.