In an earlier study1 it was observed that the levels of certain blood constituents changed from day to day in the early postpartum period in accordance with a definite pattern. It was further noted that when breast milk was compared to cow's-milk formula, a significant difference was observed in plasma urea nitrogen levels, the levels on breast milk being much lower. At that time it was hypothesized that this difference was due to the nature of the protein distribution in the two milks. The ratio of noncasein protein to casein is roughly 7:3 in breast milk and 1:3 in cow's milk.2 By noncasein protein is meant albumin, globulins, and proteoses.3
It was the purpose of this study to evaluate the effect of the ratio of noncasein protein to casein of the feeding formula on the levels of certain blood constituents and the changing levels of these constituents