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Higher Protein Intake Improves Length, Not Weight, z Scores in Preterm Infants

Olsen, Irene E.*; Harris, Cheryl L.; Lawson, M. Louise; Berseth, Carol L.

Journal of Pediatric Gastroenterology and Nutrition: April 2014 - Volume 58 - Issue 4 - p 409–416
doi: 10.1097/MPG.0000000000000237
Original Articles: Hepatology and Nutrition

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.

Address correspondence and reprint requests to Carol L. Berseth, MD, Department of Medical Affairs, Mead Johnson Nutrition, 2400 W Lloyd Expressway, Evansville, IN 47721 (e-mail:

Received 20 June, 2013

Accepted 5 November, 2013

This study was funded by the study sponsor, Mead Johnson Nutrition (MJN; Evansville, IN). C.L.H. and C.L.B. are employees of MJN. MJN provided a consulting fee to I.E.O. to interpret data and prepare the article. The other authors report no conflicts of interest.

© 2014 by European Society for Pediatric Gastroenterology, Hepatology, and Nutrition and North American Society for Pediatric Gastroenterology,