Breast milk is the safest and most complete natural food for babies. Although breast milk is crucial to the health and development of infants, the metabolites in breast milk during lactation period have not been characterized. Therefore, we examined and compared the metabolites in breast colostrum and mature breast milk using gas chromatography-time-of-flight-mass spectrometry-based metabolomics. A total of 159 metabolites were characterized, of which 72 were differentially expressed metabolites (DEMs), including 17 upregulated and 55 downregulated DEMs in breast colostrum compared to those in mature breast milk. Metabolic pathway analysis revealed that these DEMs were related to glycine, serine, and threonine metabolism; glyoxylate and dicarboxylate metabolism; alanine, aspartate, and glutamate metabolism; pentose and glucuronate interconversions; and aminoacyl-tRNA biosynthesis. Our results improve the understanding of breast milk composition and provide a theoretical basis for optimizing infant formula to closely imitate the nutrients required for proper growth and development of babies.

母乳是婴儿最安全、最完整的天然食品。尽管母乳对婴儿的健康和发育至关重要，但尚未对哺乳期母乳中的代谢物进行表征。因此，我们使用基于气相色谱-飞行时间质谱的代谢组学检查和比较了乳房初乳和成熟母乳中的代谢物。共表征了 159 种代谢物，其中 72 种为差异表达代谢物 (DEM)，其中与成熟母乳相比，乳房初乳中 17 种上调的 DEM 和 55 种下调的 DEM。代谢途径分析表明，这些 DEM 与甘氨酸、丝氨酸和苏氨酸代谢有关；乙醛酸和二羧酸代谢；丙氨酸、天冬氨酸和谷氨酸代谢；戊糖和葡萄糖醛酸相互转化；和氨酰-tRNA生物合成。我们的研究结果提高了对母乳成分的理解，并为优化婴儿配方奶粉以密切模仿婴儿正常生长发育所需的营养提供了理论依据。