Protein quality and quantity in preterm infants receiving the same energy intake

Area of Science:

• Nutritional Science
• Infant Nutrition
• Biochemistry

Background:

• Low-birth-weight (LBW) infants require specialized nutrition for optimal growth and development.
• The composition of infant formulas, particularly protein quantity and quality, significantly influences nutrient utilization and growth outcomes.
• Understanding nitrogen retention and growth parameters is essential for assessing formula efficacy in LBW infants.

Purpose of the Study:

• To evaluate the impact of varying nitrogen quantities and forms in isocaloric formulas on nitrogen retention and growth in LBW infants.
• To determine if protein quality or quantity is a more critical factor for infant growth under high-energy intake conditions.
• To identify potential critical protein intake levels influencing nitrogen retention and growth in appropriate-for-gestational-age LBW infants.

Main Methods:

• A balance study was conducted on fifteen LBW infants (1.3-1.6 kg) between 21 and 30 days of age.
• Infants were assigned to three isocaloric formulas with differing whey/casein ratios and protein hydrolysates.
• Nitrogen retention, weight gain, height, and head circumference changes were measured and analyzed.

Main Results:

• Nitrogen retention was significantly higher with 60:40 whey/casein and casein hydrolysate formulas compared to a 20:80 whey/casein formula.
• Formulas providing higher protein quantities (4.3-4.4 g/kg/day) resulted in greater weight gain and linear growth compared to the lower protein formula (3.5 g/kg/day).
• Protein quality did not significantly impact nitrogen retention or growth when protein quantity was adequate and energy intake was high.

Conclusions:

• In high-energy feeding regimens for LBW infants, protein quantity is a more significant determinant of nitrogen retention and growth than protein quality.
• A critical threshold for protein intake appears to exist, below which growth and nitrogen retention are compromised.
• These findings support the optimization of protein content in infant formulas for LBW populations.