Polyphenol metabolites in human milk: potential role in support of healthy infant development, a narrative review

Polyphenols are a broad class of phytochemicals derived from intake of fruits, vegetables, and whole grains. Due to emerging evidence linking healthy dietary patterns to maternal and child health benefits, there is increasing interest in dietary bioactives such as polyphenols in human milk. This narrative review critically evaluates evidence supporting the transfer of polyphenols to breastfed infants in human milk, potential role of maternal diet and other non-dietary characteristics (e.g., lactation duration, genetics) in modifying polyphenol composition and concentrations in human milk, and the relationship between human milk polyphenols and infant development. Over the last decade, 20 studies have reported polyphenols or phenolic metabolite concentrations in human milk. Although polyphenols can be transferred to infant circulation via human milk, evidence supporting a role for human milk polyphenols in infant development is still limited. Maternal dietary intake influences polyphenol composition and concentrations of human milk, with other reports suggesting that maternal metabotype, lactation stage, demographics, and genetics may play a role. Future studies need to include a broader assessment of polyphenols and their metabolites in human milk, their concentrations relative to clinically relevant metabolic processes, and systematic integration of additional maternal factors that may influence polyphenol metabolism or human milk composition.