Metabolism of Women During the Reproductive Cycle

Vitamin C was determined by analysis in the food as eaten each day by healthy nursing mothers and in 24-hour collections of their milk and urine during the first 10 days postpartum and 5-day periods at intervals later in lactation. In addition, vitamin C was determined in blood from the umbilical cord and in fasting samples of capillary blood from the mothers and infants. The amounts of vitamin C secreted in milk paralleled the increases in milk volume, while vitamin C excretion in the urine was high after delivery and for 3 or 4 mothers decreased 50% or more by the tenth day. No relationships between volume of milk or its vitamin C content and excretion in the urine were indicated. During the periods of secretion of mature milk, the amounts of vitamin C in the milk, in general, paralleled milk volume. For the mothers studied, whose nutritional status had been good during pregnancy, no relationship was found between vitamin C intake and secretion in milk. Excretion in urine was not related to level of intake or secretion in milk. Extreme anatomic and physiologic variability among individuals and in the same individual at different times is emphasized by the results. The data indicate also the inconclusiveness of determinations of vitamin C levels in milk, urine or fasting blood samples as an index of vitamin C nutritional status of lactating women receiving good diets. The need for further research on the physiologic influences exerted by lactation and pregnancy on vitamin C metabolism is stressed. These include adjustment of the maternal body from pregnancy to lactation, including the glands of internal secretion, the level of requirement as opposed to maximum level of storage, and differences in requirements before pregnancy, during gestation, and during lactation. On the basis of the data presented it seems that the Recommended Dietary Allowances provide for adequate amounts of vitamin C to meet normal requirements during lactation, provided the prenatal nutritional status of the mother has been satisfactory.