Factors affecting human milk lactoferrin.

We thank the authors for commenting on our article [1]. Lactoferrin (Lf) is a multifunctional protein mainly secreted by the mammary and other exocrine glands, as well as secondarily by neutrophils. It is predominantly present in external secretions such as milk, saliva, tears, bile, and pancreatic fluids [2] and is particularly abundant in human colostrum [3]. Joob & Wiwanitkit point out that it would be interesting to discuss Lf in maternal blood, as “blood Lf is markedly increased in acute pneumonia and Lf might secret into breastmilk.” However, as far as we know, there is currently no evidence that maternal blood Lf concentrations correlate with respective breast milk concentrations. Therefore, the implication of maternal blood Lf does not add, in our opinion, anything further to the discussion or interpretation of our results. Furthermore, the determination of maternal blood Lf concentrations was beyond the purposes of this study. As Joob & Wiwanitkit state, several reports have suggested that both maternal and infantile factors may affect human milk Lf concentrations [4–7]. However, those reports produced highly inconsistent results. For instance, two of the studies that the authors cite demonstrated the lack [4] and presence [5] of an association between maternal milk Lf levels and maternal age, respectively. A systematic review investigated the correlation between breast milk Lf concentrations and lactation stage, as well as maternal/infantile factors, such as race/ ethnicity, parity, maternal age, socioeconomic and nutritional status, maternal/infantile infections, and prematurity [8]. The results demonstrated that milk Lf concentrations are consistently highest in colostrum and then gradually decrease, but, besides the stage of lactation, no other maternal or infant factor is consistently associated with Lf concentrations [8]. The authors claimed that a major limitation of the published studies is the small sample size and the different methods applied to determine Lf concentrations [8]. The need for multicenter studies with large sample sizes, as well as standardized design, sample collection, and Lf measurement methods was highlighted, in order to elucidate significant factors associated with breast milk Lf concentrations [8]. Nevertheless, our study population comprised of Caucasian, hospitalized women with similar nutritional status, living in Greece, who gave birth to full-term, appropriate-for-gestational age singletons and provided a milk sample on the 3rd day postpartum, under the same conditions.