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Oxalate, citrate, and sulfate concentration in human milk compared with formula preparations: influence on urinary
1Northwestern University, Children's Memorial Hospital, Division of Pediatric Nephrology, Chicago, Illinois, USA.
Insights
Formula-fed infants show higher urinary oxalate excretion, but not due to higher oxalate levels in formula. Differences in citrate and sulfate may explain this, impacting nephrocalcinosis risk in preterm infants.
Area of Science:
- Neonatal nutrition
- Pediatric nephrology
- Biochemistry
Background:
- Nephrocalcinosis is common in preterm infants, with elevated urinary oxalate excretion as a key risk factor.
- Previous studies suggested infant formula oxalate content caused higher oxalate excretion in formula-fed infants.
Purpose of the Study:
- To compare oxalate, citrate, and sulfate concentrations in human milk and infant formulas.
- To investigate the reasons for higher urinary oxalate excretion in formula-fed infants.
Main Methods:
- Analyzed oxalate, citrate, and sulfate concentrations in 21 human milk samples and 16 infant formula preparations.
- Measured samples from early lactogenesis and established lactation stages for human milk.
Main Results:
- Oxalate concentrations in human milk increased from early to established lactation but were similar to formula.
- Human milk had significantly lower citrate and sulfate concentrations compared to infant formula.
- Wide ranges of oxalate concentrations were observed in both human milk and formula.
Conclusions:
- Higher urinary oxalate excretion in formula-fed infants is not linked to formula oxalate content.
- Infant formulas contain higher citrate and sulfate levels than human milk, potentially influencing urinary excretion.
- These findings suggest formula composition may play a role in nephrocalcinosis risk for vulnerable infants.
Background:
Nephrocalcinosis is not uncommon in preterm infants, and elevated urinary oxalate excretion is known to be one of the main risk factors. When oxalate excretion was found to be higher in formula-fed than in human milk-fed infants, the formulas' oxalate content was thought to be responsible.
Methods:
The oxalate concentration in human milk (21 samples obtained during lactogenesis; 17 samples obtained during established lactation) and of 16 formula preparations was examined. Citrate and sulfate concentrations were also measured, because both anions influence urinary saturation.
Results:
The mean (+/- SE) oxalate content of human milk increased approximately 27% from early lactogenesis (70.4 +/- 6.4 micromol/1) to established lactation (96.4 +/- 9.5 micromol/l; p < 0.05). The latter was not different from the mean oxalate concentration of formula (98.2 +/- 11.4 micromol/l), however a fourfold range of measurements was recorded in both groups. The mean citrate content of human milk increased only slightly after early lactogenesis (2.66 +/- 0.22 mmol/l), but remained significantly lower than in formula (3.34 +/- 0.23 mmol/l; p < 0.05). The mean sulfate concentration did not increase and was 13 times lower in human milk (52.1 +/- 9.5 micromol/l) than in formula (688.7 +/- 95.4 micromol/l; p < 0.0001).
Conclusions:
The higher oxalate excretion in formula-fed infants is not because of the milk's oxalate concentration. Urinary citrate and sulfate excretion may be influenced by their higher concentrations in formula preparations, which may be of clinical importance in the population that is at risk for development of nephrocalcinosis.