17 - Standard infant formulas

Summary

Term infant formulas do not meet the nutritional requirements for VLBW infants. Yet many preterm babies may be discharged on term formulas and some even receive them in the NICU. The carbohydrate in standard infant formula is 100% lactose and the fat is all long-chain triglycerides of vegetable origin, usually soy and coconut oils. Most standard formulas are whey-predominant, with 60% of the protein whey and 40% casein. Standard formulas are available in both iron-fortified and non-iron-fortified (or “low iron”) forms. Iron-fortified formula contains elemental iron 12 mg/L or approximately 2.0 mg/kg per day for an infant receiving approximately 108 kcal/kg/d. Low-iron formula contains elemental iron 1.5 mg/L or 0.2 mg/kg per day.

Most standard infant formulas are available as ready-to-feed, liquid concentrate, and powder. The concentrate and the powder provide the option of concentrating the formula to a higher caloric density. Concentrations above 1 kilocalorie per milliliter or 30 kilocalories per ounce are not recommended because of the high renal solute load that results from the decrease in free water intake. As the formula is concentrated, the osmolality increases to approximately the same degree as the concentration. Thus, for a 20 kcal/oz formula with an osmolality of 300 mOsm/kg H₂O, if concentrated 135% or to a 27 kcal/oz formula, the osmolality increases to approximately 405 mOsm/kg H₂O. This concentration of term formula is not an accepted strategy for nutrient-enhancing a VLBW infant in the NICU. The chapter on hypercaloric feeding strategies (Chapter 22) discusses acceptable milks where over concentrating is not a likely hazard for small preterm infants.