Enteral calcium, phosphate and vitamin D requirements and bone mineralization in preterm infants

With major advances in life-support measures, nutrition has become one of the most debated issues in the care of very low birth-weight (VLBW) infants. Current nutritional recommendations are based on healthy premature infants and designed to provide postnatal nutrient retention during the 'stable-growing' period equivalent to the intrauterine gain of a normal foetus. However, this reference is still a matter of discussion, especially in the field of the mineral requirements. After birth, there are dramatic physiological changes in bone metabolism resulting from various factors: disruption in maternal mineral supply, stimulation of calciotropic hormone secretion, change in hormonal environment and relative reduction in mechanical stress. These events stimulate the remodelling process leading to an increase in endosteal bone resorption and a decrease in bone density. In preterm infants, these adaptation processes modify the mineral requirement, since, by itself, the increased remodelling provides a part of the mineral requirement necessary for postnatal bone growth and turnover. The care of newly born premature infants should not necessarily aim to achieve intrauterine calcium accretion rates.

Considering that a calcium retention level ranging from 60 to 90 mg/kg/day assures appropriate mineralization, and decreases the risk of fracture and diminishes the clinical symptoms of osteopenia, an intake of 100 to 160 mg/kg/day of highly bioavailable calcium salts, 60 to 90 mg/kg/day of phosphorus and 800 to 1000 IU of vitamin D per day is recommended.