Two cases of black human breast milk not related to minocycline. A sphingolipidomic approach

Different colors of human breast milk (HBM) are reported in literature, and black milk is produced only during minocycline therapy. We herein report two cases of black/dark gray color HBM without minocycline involvement. We analyzed both milk samples and compared the data with two control HBM samples taken from two mothers who had the same dietary behaviors and took the same supplements (iron) as done by the mothers under study. Results indicated that the black color was not due to iron intake, disease or infection. With Sudan III stain, specific for lipids, dark precipitates were evident. Antioxidant power was much higher in studied milk samples than in control samples. As antioxidants at high levels become pro-oxidants, our data suggested possible lipid oxidation. Sphingolipid profile of black milk samples demonstrated accumulation of sphingomyelin and ceramide, which could be a sign of impaired lipid metabolism. It was concluded that iron supplementation was not responsible for HBM pigmentation, but altered biochemical mechanisms in the mammary gland could be implicated. In our experience, dark color HBM did not represent an absolute indication for discontinuation of breastfeeding.