The calcium-binding S100B protein is concentrated in glial cells (including enteroglial cells) in the nervous system. Its conformation and amino acid composition are significantly conserved in different species
this characteristic suggests conserved biological role(s) for the protein. The biological activity is concentration-dependent: low physiological concentrations exert a neurotrophic effect, while high concentrations exert a proinflammatory/toxic role. The proinflammatory/toxic role of S100B currently attracts the scientific community's primary attention, while the protein's physiological action remains unraveled-yet remarkably interesting. This is now a topical issue due to the recently consolidated notion that S100B is a natural trophic nutrient available in breast milk and/or other aliments, possibly interacting with other body districts through its impact on microbiota. These recent data may offer novel clues to understanding the role of this challenging protein.