Postdischarge nutrition in infants born <32 weeks gestation and/or <1500 grams birth weight: relation with growth, body composition and metabolic health at 7 years (STEP 2)

Early and aggressive feeding protocols in term low birth weight infants leading
to increased growth in the first year of life are associated with increased
risk of disease later in life, such as diabetes, cardiovascular disease and
obesity. Preterm infants already are at risk for adverse metabolic effects,
which may be explained by the *fetal origins hypothesis* and the *catch up
growth hypothesis*. Insulin resistance and salt sensitivity are suggested to be
major factors in the association between prematurity and diseases in later
life. In preterm born children and adolescents the tendency to retain salt may
become a central mechanism for the development of hypertension and
cardiovascular risk and is also important for developmental outcome. Early
nutritional interventions, especially low salt intake, may decrease salt
sensitivity. Higher protein intake with postdischarge formula between term date
and 6 months corrected age results in more lean mass and less fat mass. It is
hypothesized that infants fed postdischarge formula have more lean mass, less
fat mass, lower blood pressure, decreased salt sensitivity and higher bone
mineralization at 7 years compared to those fed term formula. Infants fed
postdischarge formula are hypothesized to be comparable to infants fed human
milk at 7 years.

The main objective of the study is to evaluate differences in body size, body
composition and metabolic health at 7 years between children fed postdischarge
formula and term formula. Secondary objectives are differences in bone
mineralization and development at 7 years between children fed postdischarge
formula, term formula and human milk. Also, differences in body size,
composition and metabolic health at 7 years between children fed postdischarge
formula and human milk are evaluated.

This study is an interventional and observational follow up study.

A high salt diet is used for 7 days. The extra salt is provided as dietary
sodium chloride supplements in a dose of 0.12 gram/kg body weight per day.

Subjects will be asked to visit our outpatient clinic twice. Subjects are asked
to collect three salivary samples before the first visit. Before resp. the
first and second visit a regular diet and high salt diet is used for 7 days and
a three day dietary dairy is kept. At both visits blood pressure will be
measured and a fasting blood sample is collected for hormonal, renal and
cholesterol parameters to evaluate metabolic health. On day 1 and 2 resp. 23.5
and 15.5 ml blood is drawn. Anthropometry, whole body DEXA scan and
developmental tests will be performed.