The requirement for protein, and the utilization of protein and calcium during pregnancy

Abstract

The influence of diet on the course and outcome of pregnancy was studied in the rat. The protein value of the diet fed during pregnancy had no effect on the number and composition of the fetuses, and a slight effect only on individual fetal weight. On a diet providing 5.9 per cent of the total calories as wholly-utilizable protein (NDpCal per cent 5.9) there occurred a significant loss of protein from the maternal carcass accompanied by a rise in body fat. The liver was enlarged, and its content of protein, ribonucleic acid, phospholipid and neutral fat was increased. On diets of NDpCal per cent 10.0 and 13.0, the carcass showed no net gain or loss of protein, but fat reserves were greatly augmented. The changes in liver size and composition were more marked. Analyses suggested that the fat deposited in the liver during pregnancy was not derived from the diet, nor was it mobilized from fat depots, but was synthesized, under the influence of a placental factor, from carbohydrate or protein. During the first 14 days of pregnancy, a reserve of protein and fat was laid down in the mother's tissues. Over the last 7 days, carcass protein was catabolized. A scheme for the endocrine control of protein metabolism in pregnancy is postulated. It accounts for the inability of the rat to store protein in late pregnancy, and provides a physiologic mechanism whereby the fetus is protected from the injurious effect of an inadequate maternal diet. Evidence was obtained against the concept of calcium storage during pregnancy.