CONCENTRATIONS OF BIOTIN METABOLITES IN HUMAN-MILK

Because estimates of the biotin requirement for infants currently are based on the biotin concentration in human milk, we sought to determin e whether inactive boitin metabolites are present. Samples were collec ted for 7 weeks post partum from 15 healthy women. Biotin and the inac tive metabolites bisnorbiotin and biotin sulfoxide were measured by me ans of a high-performance liquid chromatography avidin-binding assay. At 8 days post partum the proportion of biotin was 44%, bisnorbiotin 4 8%, and biotin sulfoxide 8%. Although biotin content increased post pa rtum (p < 0.003), the metabolites remained an important portion of the total providing evidence that accurate measurement of biotin in human milk requires an assay that is specific for biotin.