A New Dietary Deficiency With Highly Purified Diets.

In the course of our work on vitamine E it became necessary some years ago to attempt to withdraw all traces of this substance from dietaries. But various workers, including ourselves, have reported inferior animals when ordinary casein is extracted for a long time with solvents for E—alcohol and ether. This effect could be due to removing impurities or to lowering the nutritive value of the protein itself. The solution of this problem is obviously facilitated by purity and hence constancy in the remaining ingredients of the diet. It is established that the rat can use without embarrassment either fat or carbohydrate alone for the complete satisfaction of its caloric needs. The use of starch as a source of energy involves the inclusion of many impurities. The recent papers of Taylor and Iddles, for example, show that cornstarch contains about 0.6 per cent of fatty substance, which is within the granule and is non-extractable. The use of sucrose has been decided upon after a comparison of this sugar with chemically pure glucose and chemically pure lactose. The former offers no advantage and lactose proved entirely unsuitable, since the animals soon declined and died apparently because of intestinal disturbances. The sucrose is made by recrystallizing the best grade of commercial cane sugar from 80 per cent alcohol. The casein is prepared according to Van Slyke, and is a dry white powder which has no ether extractable material and an ash content of not over 0.2 per cent. The salts are of the highest purity obtainable in the market. The pure diet employing these substances (our Diet 519) is as follows: The animals are taken at 21 days of age and kept in inclividua1 metablolism cages so there is no access to feces or urine.