Lesson 1: Defining the Nutritional Needs of Preterm Infants
Lesson 1: Defining the Nutritional Needs of Preterm Infants
As discussed on the previous unit, nutrition is a valuable tool in the management of the preterm infant, especially those born VLBW and ELBW. Research has demonstrated remarkable importance for early nutrition and growth towards favorable long term outcomes. However, meeting this nutritional requirement is still a challenging task to health care providers and parents alike (Uauy & Koletzko 2014).
Nutritional need is defined as:
"the amount and chemical form of a nutrient needed to support normal health, growth and development without disturbing the metabolism of other nutrients”
(Uauy & Koletzko 2014).
This nutritional requirement is established based on the needs of "healthy” individuals. However, most preterm infants cannot be considered as "healthy” as a term infant, making their nutritional needs unique.
In figure 1, the curve demonstrates the usual way to depict nutritional needs. AR is the acceptable range of intakes, where physiological requirement of the nutrient is met without causing damage. The first peak is the Estimated Average Requirement (EAR), which is calculated from a group of individuals. The Gaussian curve is calculated based on this value, with the 2.5th percentile being the Lowest Threshold Intake (LTI), the value where almost all individuals will not be able to keep metabolic integrity for that particular nutrient. The 97.5th percentile is the Recommended Daily Allowance (RDA) also Reference Nutrient Intake (RNI) or Population Reference Intake (PRI), being the daily intake which 97.5% of the individuals will be able to meet the nutrition requirement. The Upper Safe Level of Intake (UL) is the value marking the maximum intake before the appearance of adverse effects. The UL should be carefully calculated for preterm infants, taking in consideration all sources of intake (enteral or parenteral).
Figure 1. Nutrient intake curve.
LTI= lowest threshold intake;
EAR= estimated average requirement;
RNI=reference nutrient intake;
PRI=population reference intake;
RDA= recommended dietary allowance;
UL=upper safe level of intake;
AR= acceptable range of intakes.
Source: Uauy & Koletzko 2014, reprinted with permission of S. Karger AG, Switzerland
For preterm infants the nutrients requirements are normally derived from the AR. When the EAR has been established for a specific nutrient (by means of observational studies and/or clinical evaluation), it will represent the lower value of the AR. The upper value is normally lower than the UL, once the UL has been established for bodyweight-GA specific group.
"The AR should be applied as a range of intake for individuals within a group that is homogeneous in term of age, birth weight, and other characteristics believed to affect nutrient requirement.”
(Uauy & Koletzko 2014).
In the next lessons, specific nutrient recommendations will be presented, whenever possible, as range of intakes for a certain group of preterm individuals. However, one should keep in mind that the preterm population is a very heterogeneous group. Therefore, each case should be individualized by the health care provider based on clinical condition, metabolic status, and feeding tolerance.