Enteral Zinc to Improve Growth in Infants at Risk for Bronchopulmonary Dysplasia

Multiple factors contribute to growth failure in infants with BPD, including poor nutrient stores, inadequate intake, increased losses, and increased needs. Furthermore, compared to infants without BPD, those with BPD have increased resting metabolic rates and energy expenditure. Growth deficits manifest as lower weight, length, and head circumference, as well as changes in body composition. These deficits precede the development of BPD and persist post-discharge. While similar rates of growth are observed in very low birth weight infants with and without BPD once receiving equal calories, catch up growth does not occur in the BPD group. Thus, early growth deficits remained uncompensated.

After iron, zinc is the most metabolically active trace element in the human body. It has a critical role in growth, through its actions on growth hormone, IGF-1, IGFBP-3, and bone metabolism. Prematurity is a risk factor for zinc deficiency, as 60% of zinc accretion occurs in the third trimester. Impaired intake and absorption or excess excretion can further increase this risk. Finally, periods of rapid growth, as seen in preterm infants, increase the need for zinc.

Biochemically, zinc deficiency is defined by a serum zinc level less than 55mcg/dl. However, while zinc depletion is associated with deficiency, the opposite may not be true. For example, in starving patients, clinical symptoms of zinc deficiency occur during re-feeding, suggesting overall requirements are related to needs, regardless of overall zinc status. This may be the case in preterm infants, who may have a subclinical deficiency despite serum zinc level. Thus, zinc deficiency should be considered in infants with poor growth despite receiving adequate protein and calories.

The objective of this study is to determine whether enteral zinc supplementation leads to improved growth in infants at risk for bronchopulmonary dysplasia (BPD). The investigator's hypothesis is that enteral zinc supplementation in very preterm infants at high risk for BPD will significantly improve growth compared to standard of care.