Neonatal nutrition has to face a contradictory and conflicting nutritional regimen like a high percentage of amino acids from the first day of life in order to achieve normal neurodevelopment versus metabolic complications (insulin resistance, hyperglycemia, increased visceral fat) that this type feeding, in conjunction with complexity of prematurity, is likely to cause. Current study aims to investigate is whether individualized fortification of breast milk protein, based on the mother's milk protein content and targeting the recommended daily protein requirements, is associated with better nutrition, growth, biochemical and endocrine markers associated with the nutrition of preterm low birth weight neonates, compared to the standard fortification of human milk.

Proteins are of the most important macromolecules in living organisms participating in almost all biological processes. Premature infants are forced to adapt to a new (extrauterine) environment where supply of nutrients, including amino acids, from mother ceases abruptly. Consequently, the aim of neonatologist is the appropriate, quantitatively and qualitatively nutritional support, to promote brain development, achieve normal endocrine and metabolic function, maintain a growth rate similar to the intrauterine one avoiding extrauterine growth restriction during postnatal period and at the same time encouraging the analogue modulation of body composition (increased muscle mass, decrease body fat, hydration).

Malnutrition or inadequate nutrition of preterm infant which remains undiagnosed and without proper treatment could have serious consequences on psychomotor development and metabolic activity. Indeed, 75% of low birth weight premature infants exhibit extrauterine growth restriction at discharge, even when they have achieved growth equal to the considered satisfactory, ie 15g/kg/day.

Beyond anthropometrics differences between preterm and full-term newborns, body composition varies as well. Preterms have higher percentage of body fat and decreased muscle mass at term time compared with full term neonates. However, it has not been clarified whether this differentiation is harmful predisposing to chronic diseases later in childhood or adult life (eg. obesity, metabolic syndrome).

Inclusion Criteria:

• Infants with gestational age ≤ 34weeks
• very low birth weight (≤ 1500g)

Exclusion Criteria:

• maternal health problems contradicting breastfeeding
• genetic or chromosomal abnormalities
• metabolic contraindications for increased amount of protein