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.