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Associative Dynamic Effects of Protein, Carbohydrate and Fat¹

Two Figures

Institute of Animal Nutrition, The Pennsylvania State College, State College

A study was made, with mature albino rats as subjects, of the dynamic effects of beef protein, cerelose (corn sugar) and lard, individually and variously combined, at planes of nutrition above maintenance; the dynamic effects being measured by difference between the heat production of the subjects as established on a complete basal diet and on the same plus the nutritive supplements.

The supplementary feeding of protein, of carbohydrate or of fat increased the production of heat from the kind of nutriment fed. Cerelose spared protein and fat; beef protein spared carbohydrate and fat; while lard spared only protein.

Of the mixed supplements, cerelose and beef protein increased heat production from carbohydrate and protein, and spared fat; cerelose and lard increased heat production from carbohydrate, and spared protein and fat; beef protein and lard increased heat production from protein, and spared carbohydrate and fat; while cerelose, beef protein and lard increased heat production from protein and carbohydrate, and spared fat. All mixed supplements, regardless of composition, spared fat.

Fed as supplements to a complete diet sufficient for maintenance, the dynamic effect of beef protein was 32%, of cerelose 20%, and of lard 16% of its gross energy.

The dynamic effects of mixed supplements of protein and fat, and of carbohydrate and fat, were lower even than the dynamic effect of fat. In this sense fat is much more potent than are protein and carbohydrate in determining the dynamic effects of diets.

Among four supplemental combinations of protein, carbohydrate and fat, computed to 1000 cal. of gross energy, the one with the lowest dynamic effect was that of protein and fat, followed closely by the combination of carbohydrate and fat; then by the combination of protein, carbohydrate and fat; while the combination with the highest dynamic effect was that of carbohydrate and protein.

The observed dynamic effect of carbohydrate and protein was 12.5% less, of carbohydrate and fat 35% less, of protein and fat 54% less, and of carbohydrate, protein and fat 22% less, than as computed from experimentally determined values for the individual nutrients.

The dynamic effects of diets are not the additive dynamic effects of their components; the prevalent idea that the dynamic effects of diets vary in the order of their protein contents is incorrect; and inasmuch as there is no scientific means of apportioning energy effects or values among dietary constituents, the dynamic effects of individual foods or nutrients are without significance as constants.

Manuscript received 23 December 1943.