Forms and Amounts of Vitamin B12 in Infant Formula: A Pilot Study

PurposeInfant formula is based on cow’s milk and designed to mimic breast milk for substitution. Vitamin B12 (B12) is bound to proteins in both breast milk and cow’s milk, and in milk from both species the vitamin occurs mainly in its natural form such as hydroxo-B12 with little or no synthetic B12 (cyano-B12). Here we test commercially available infant formulas.MethodsEleven commercially available infant formulas were measured for content of B12 and analyzed for the presence of B12-binding proteins and forms of B12 using size exclusion chromatography and HPLC.ResultsAll infant formulas contained B12 by and large in accord with the informations given on the package inserts. None of the formulas contained protein-bound B12, and cyano-B12 accounted for 19–78% of the total amount of B12 present, while hydroxo-B12 constituted more or less the rest.ConclusionsThis pilot study shows that infant formula differs from breast milk in providing the infant with free B12, rather than protein-bound B12, and by a relative high content of cyano-B12. The consequence of supplying the infant with synthetic cyano-B12 remains to be elucidated.研究目的 婴儿配方奶粉以牛乳为基质，旨在模拟母乳以作为母乳替代品。母乳与牛乳中的维生素B12（Vitamin B12，简称B12）均与蛋白质结合，两类乳源中的该维生素主要以天然形式存在，例如羟钴胺（hydroxo-B12），几乎不含或仅含极少量合成型维生素B12（氰钴胺，cyano-B12）。本研究针对市售婴儿配方奶粉开展相关测试。 研究方法 本研究选取11款市售婴儿配方奶粉，对其B12含量进行检测，并通过尺寸排阻色谱法（size exclusion chromatography）与高效液相色谱法（HPLC）分析样品中B12结合蛋白的存在情况以及B12的存在形式。 研究结果 所有受试婴儿配方奶粉的B12含量均与产品包装说明书所标注的信息基本一致。所有受试配方奶粉均未检出结合蛋白型B12；氰钴胺（cyano-B12）占总B12含量的19%~78%，剩余部分则基本为羟钴胺（hydroxo-B12）。 研究结论 本初步研究表明，婴儿配方奶粉与母乳存在显著差异：其为婴儿提供的是游离型B12而非结合蛋白型B12，且氰钴胺（cyano-B12）含量相对较高。为婴儿摄入合成型氰钴胺所带来的潜在影响仍有待进一步阐明。