Nutrition Studies in the Cold

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Abstract
Immature and young adult male rats received a series of 8 choline-and inositol-free diets varying in protein content from 5 to 40% (with 20% fat) and in fat from 10 to 40% (with 20% protein). Parallel groups were maintained at 1° and at 25°C. With the immature rats at 5 and 10% protein levels the growth rate and protein efficiency ratio were higher at 1° than at 25°. The reverse was true at protein levels of 20, 30 and 40%. The growth rate was higher at 25° than at 1° on the 10, 20, and 30% fat levels. With 40% fat the growth rate was higher at 1°. At 25° the liver lipids in the immature rats were highest on the 5% protein diet and dropped regularly and sharply up to 30% protein. At 1° the liver lipids were essentially the same at all protein levels and were in the normal range for the rat. Increasing the fat content of the diet from 10 to 40% produced a regular increase in liver lipids at 25° while at 1° there was no significant change and the liver lipids were in the normal range at all fat levels. The observations on the young adult animals were qualitatively the same as for the immature rats. The dietary requirement for lipotropic factors appeared to be lower at 25° for the adult animals. The food and calorie intake was higher at 1° for both groups of animals. The mechanism of the lipotropic effect of cold is discussed.