Protein Requirements of Low Birthweight, Very Low Birthweight, and Small for Gestational Age Infants

A definition of the protein requirement of any population must include consideration of the purposes for which the requirement is being defined. For the normal adult, the requirement addresses primarily the needs for maintenance (i.e., the exogenous protein needed to maintain nitrogen equilibrium and hence body protein stores). The protein requirement of any pediatric population, particularly that of low birthweight (LBW) infants, includes the needs for maintenance plus the additional needs to assure normal growth. In addition, if there has been a period of delayed or subnormal growth, either in utero or ex utero, and/or if actual weight loss has occurred, as is true for most LBW infants, there is an additional need to support catch-up growth. Another consideration in defining protein requirement is related to maintenance of plasma indices of protein adequacy and excess. In general, a protein intake that meets the maintenance needs of adults or supports normal growth of infants and children will also support normal rates of synthesis of all proteins and hence normal plasma concentrations of the proteins commonly considered indices of protein adequacy (e.g., albumin and transthyretin). Thus the concern is usually that the protein intake should not exceed metabolic capability, resulting in raised plasma indices of protein excess (e.g., urea and amino acids).