Levels of S100B protein are higher in mature human milk than in colostrum and milk-formulae milks

Background & Aims: Human milk is believed to contain biological factors involved in the regulation of newborn growth, including brain development. Recently, it has also been shown to contain the calcium-binding S100B protein, regarded as a neurotrophic factor. The present study investigates the concentrations of this protein in colostrum, human milk at different levels of maturation and in milk-formulae. Methods: Samples for S100B measurements were collected from human colostrum (on day 1 after birth), from transition milk (on post-delivery days 7 and 14) and from mature milk (on day 30 after delivery) in 14 healthy women and from 14 milk-formulae. The S100B protein levels were measured using a commercially available specific immunoluminometric assay. Results: Mean S100B protein levels were significantly higher in mature human milk (117.9±36.7 μg/l) than in transition milk at 14 days (106.7±38.1 μg/l) and at 7 days (92.7±37.8 μg/l), colostrum (74.6±37.6 μg/l) or milk-formulae (24.8±19.5 μg/l) (P<0.001, for all). A correlation between human milk S100B levels and the gestational age at which samples were obtained was also found (r=0.39; P<0.01). Conclusions: These findings, possibly related to S100Bʹs neurotrophic role, offers useful information to the investigation of the role of S100B protein in brain maturation.