Maternal diet during breastfeeding in correlation to calcium and phosphorus concentrations in human milk

The impact of maternal diet on mineral concentration in human milk (HM) remains unclear. The main aim of this study was to investigate the relationship between maternal dietary intake and calcium and phosphorus concentrations in HM. Furthermore, we aimed to evaluate the intake of both minerals by exclusively breastfed infants.

HM samples were obtained from 30 mothers at 6-8 weeks postpartum. Each mother was asked to express pre- and postfeeding milk four times during a 24-h period (6.00-12.00, 12.00-18.00, 18.00-24.00, 24.00-6.00). Maternal dietary assessment was based on a food frequency questionnaire and 3-day dietary records. Analysed minerals were determined using an inductively coupled plasma mass spectrometer (NexION 300D ICP mass spectrometer, Perkin Elmer SCIEX).

The mean concentrations of calcium and phosphorus in HM samples were 278.7 ± 61.0 and 137.1 ± 21.9 mg/L, respectively, maintaining 2:1 ratio by weight. The concentration of both minerals was correlated with each other (r = 0.632, p = <0.001). The infants' mean calcium intake was 149.53 ± 36.41 mg/L, and their mean phosphorus intake was 74.62 ± 19.41 mg/L. The risk of insufficient intake of calcium was reported in 60% of infants (n = 18). Spearman's/Pearson's correlation coefficients did not reveal any correlations between HM calcium concentration and maternal diet, contrary to HM phosphorus concentration, which was positively correlated with energy (r = 0.369, p = 0.045), total protein (r = 0.464, p = 0.01), calcium (r = 385, p = 0.036), phosphorus (r = 501, p = 0.005), niacin (p < 0.001) and pyridoxine (r = 382, 0.037) intake. However, in multivariable analysis we observed that maternal dietary intake of both minerals had a positive influence on their concentration in HM.

Maternal calcium and phosphorus intake influenced the concentration of both minerals in HM; however, the relationship was rather weak. In addition, we observed that calcium intake by most of the exclusively breastfed infants was insufficient to meet the recommended daily intake.