110
Abstract
[Vol. XVIII, Part II,
The net utilization transfer of food energy to a form of energy useful to man—of all well-balanced
rations is a maximum constant. As a deficiency unbalances a ration, the efficiency of energy utiliza-
tion is decreased either through a decrease in food intake or an increase in the metabolic rate or the
calorigenic effect of the diet.
Most mineral deficiencies decrease the appetite and increase the wastage of food energy as animal
heat. Potassium, magnesium and calcium deficient rats require more food than the corresponding
controls to attain the same body-weight. Same is true of cows maintained on a low phosphorous
ration.
Vitamin deficient rats cease to grow before showing a decrease in their appetite. The decreased
utilization is due primarily to lack of an anabolic principle in the vitamin and secondly to a depraved
appetite. Among other things, vitamin C raises the power of endurance of the consumer. Vitamin
B is specific in the production of fats from carbohydrates with an increase in oxidation and it also
regulates the efficiency of muscular work. Riboflavin is related to the metabolic enzymes. Its
deficiency in rats raised the calorigenic action of food and decreases protein and fat storage. But for
slight lowering of the protein storage vitamin A deficiency does not affect the energy utilization.
Recently, however, it has been observed that the higher protein storage in vitamin A supplied controls
is accompanied by a higher retention of fat and water.
The catabolism and hence the partial calorigenic action of a particular aminoacid is decreased
by its deficiency and this is true for all proteins. But in a protein-deficient-diet, the decreased
catabolism is over-compensated by an increased oxidation of carbohydrates and fats. Expressed
per unit of metabolic body size there is no difference in the metabolic rates of a deficient or a control
rat. This rate of a deficient rat is observed to decrease or to increase according as the comparison
is made against a control on an unlimited food-intake or against one whose food-intake is restricted
to that of the deficient rat. The differences introduced by the body size and the reduced food intake
are eliminated in the latter and is the per se effect of the deficiency. Even this per se effect is the
sum total of several inter-related tendencies.
The potassium deficiency per se increases the metabolic rate. But for brain tissue the rate of
oxygen consumption of the tissues in vitro is depressed by increasing potassium concentration in the
medium.
Magnesium and calcium activate phosphatases. The latter is particularly responsible for
liberating energy for muscular work by the breakdown of adenosine triphosphatase. The changes
in metabolic rate on account of the deficiency of these minerals are only apparent. The per se effect
in both the deficiencies being towards an increase. In general their increasing concentration depresses
nerve respiration in vitro. The decreased calcium concentration stimulates the oxidation-rate of
tissues in virto.
Lack of iron through anæmia impairs the oxygen-supply in the organism. However, as is
evident from the contrary references available, the deficiency of this element has no significant effect
on the metabolic rate.
Iodine as a component of thyroxine has an unique role in controlling the metabolic rate. Though
iodine deficiency in rats tends to lower the metabolic rate, it is ingestion of the iodized salt that lowers
the high metabolic rate during pregnancy.
Phosphorous is important in biological energy transfer. However the deficiency of this mineral
produces no significant difference in the rate of oxygen consumption. In vitro, kidney slices have a
higher rate in phosphorous-free-medium but the nerve tissues consume more oxygen on addition of
phosphate. Ascorbic acid has only a doubtful significance in animal respiration. The literature on
the subject does not give a satisfactory picture of the influence of the deficiency on the metabolic
rate of animals or that of tissues in vitro.
Vitamin B, is significant in biological breakdown of carbohydrates. The deficiency of this
vitamin has a depressing effect on the respiratory exchange of birds, hens and rats. The low metabolic