Calcium, phosphorus and magnesium balance: FM 85 fortification of human milk does not meet mineral needs of extremely low birthweight infants.

OBJECTIVE: Extremely low birthweight (<1000 g) infants are growing rapidly and their nutritional requirements for calcium, phosphorus, magnesium are high.
DESIGN: Prospective, mineral balance.
SETTING: The study was carried out at the Department of Neonatology, Virchow-Hospital, Charité Berlin and the Department of Molecular Trace Element Research, Hahn-Meitner-Institute Berlin.
SUBJECTS: Nineteen infants <1000 g birthweight were admitted, nine infants dropped out and 10 infants (birthweight 730-995 g), fed fortified human milk were included. INTERVENTION: We collected infant's urine and feces for 72 h, a sample of human milk and infant's blood at 7 and 12 weeks of age. Elements were measured by inductively coupled plasma atomic emission spectrophotometry.
RESULTS: Mean (s.d.) mineral concentration in milk was low especially at 12 weeks: calcium 9.88 (+/-3.58) mmol/l, phosphorus 7.02 (+/-3.81) mmol/l, magnesium 1.59 (+/-0.54) mmol/l. Calcium retention was minimal or negative during the study, whereas phosphorus and magnesium balances were positive. Caffeine and diuretics increased mineral excretion. Serum alkaline phosphatase was mostly <800 U/l, and 162 U/l in one infant with zinc deficiency at 12 weeks. Alkaline phosphatase correlated with absorption and retention of phosphorus, and with longitudinal growth.
CONCLUSIONS: Infants <1000 g have high nutritional needs for calcium, phosphorus and magnesium, which are not met by a human milk fortifier widely used in Europe. Controlled trials are needed to assess requirements, duration and risks of mineral supplementation.