The optimal diet for the low birthweight infant is one that supports a growth rate approximating that of the third trimester of intra-uterine life without imposing stress on the developing metabolic or excretory systems. Although preterm human milk does not meet the energy and nutrient needs of developing preterm infants, the benefits such as contributions to host defence and gastrointestinal trophic aspects, and the psychological benefits of maternal-infant bonding, make it the preferred diet.