[Protein requirements of young infants. The effect of protein content in food on growth, protein intake and protein...

The protein content of human breastmilk as given by different authors does not agree very well (table I). This may be caused by the stage of lactation and the nutritional state of the mother, which influences the composition of the milk. Likewise there is no agreement in literature concerning the recommended minimum protein level in infant formulae (table II). Generally the protein level in infant formulae is significantly higher than in human breastmilk. In our experiments the growth of new-born infants fed on a formula with a rather low protein level (1,4 g/100 ml) and with an average protein level (1,9 g/100 ml) was compared (table IV). The experimental stage covered the age from 4 weeks up to and including the twelfth week. In the first four weeks of life the infants were breast-fed; after twelve weeks some additional food was given. Both weight and length were recorded of boys as well as girls. No statistically significant differences were observed on the two different formulae. The growthcurves fit very well with the growth of the Dutch infants (graphics). The average weight increase was under all circumstances somewhat higher on the milk with the lower protein content, these differences however were statistically not significant (table V). No significant differences were seen in the food-intake (table VI and VII). The average food efficiency (weight gained per 100 ml of food) was always the highest on the low protein formula. This effect is however not statistically significant. The food efficiency decreased with increasing age. Boys showed a higher food efficiency than girls. The protein intake (grams per kg bodyweight) was of course lower with the low protein formula (table IX). From an average weight increase of about 30 g a day (table V) and the average protein content of the infant, an average protein increment of 3,4 grams a day was calculated. This means that at a body weight of 3500 grams and a milk-intake of 150 ml/kg a day the protein-intake will be respectively 7,4 and 10,0 grams a day with formulae of respectively 1,4 and 1,9 g protein/100 ml. These daily intakes diminished with the daily protein increment of the infant lead to an amount of respectively 7,4 minus 3,4 leaving 4,0 and 10,0 minus 3,4 leaving 6,6 grams of protein that must be metabolized and must be excreted with the urine respectively as 23 mmol and 38 mmol of urea.(ABSTRACT TRUNCATED AT 400 WORDS)