Higher protein intake improves length, not weight, z scores in preterm infants.
OBJECTIVE
The aim of the study was to evaluate the relation between nutritional intake (kilocalories, protein) and weight and length growth in preterm infants, and to describe their metabolic tolerance with a focus on those with high protein intake (≥ 4.6 g · kg(-1) · day(-1)).


METHODS
Secondary analysis of data from appropriate-for-gestational age preterm infants in a 28-day randomized clinical trial that evaluated growth, tolerance, and safety of a new ultraconcentrated liquid human milk fortifier (original study n = 150). This subset of 56 infants had complete growth and nutrition data and met criteria for the original study's "efficacy analysis" (eg, >80% of kilocalorie intake from study diet). Nutritional intake was estimated, not actual. Regressions were used to test cumulative kilocalories and protein as the predictors of 28-day change in weight and length z scores (growth status), and to evaluate protein tolerance.


RESULTS
Average intake was 118 ± 8 kcal · kg(-1) · day(-1) and 4.3 ± 0.4 g protein · kg(-1) · day(-1), with 16 ± 3 g · kg(-1) · day(-1) and 1.1 ± 0.2 cm/week growth for 28 days. Cumulative total kilocalories and protein were significant predictors of improved length z score (P = 0.0054, 0.0005) but not weight z score change. Regression models indicated that protein not kilocalories explained the improvement in length z score, with protein explaining 19% of the variability. The high protein group averaged 4.6 to 5.5 g · kg(-1) · day(-1) (n = 16). Protein tolerance was adequate for all of the study infants based on metabolic measures (blood urea nitrogen, serum carbon dioxide, pH).


CONCLUSIONS
Higher cumulative protein intake was tolerated and overall lessened the commonly occurring decline in the length but not weight growth status in a 28-day study of preterm infants.
*School of Nursing, University of Pennsylvania, Philadelphia, PA †Department of Medical Affairs, Mead Johnson Nutrition, Evansville, IN ‡Department of Mathematics and Statistics, College of Science and Mathematics, Kennesaw State University, Kennesaw, GA.
Irene E
IE
Olsen
Cheryl L
CL
Harris
M Louise
ML
Lawson
Carol L
CL
Berseth
D000136:Acid-Base Equilibrium; D001806:Blood Urea Nitrogen; D001827:Body Height; D001835:Body Weight; D002245:Carbon Dioxide / Q000097:blood; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000009:adverse effects; D019587:Dietary Supplements; D002149:Energy Intake; D005260:Female; D005527:Food, Fortified; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature / Q000254:growth & development*; D008297:Male; D008895:Milk, Human
D004044:Dietary Proteins; D002245:Carbon Dioxide