Human milk cobalamins

Humans receive cobalamins from food— mainly from meat and meat products, and to a lesser extent from milk and milk products. Cobalamins are found in food in five forms hydroxycobalamin, AdoCbl, MeCbl, suphitoco-balamin and cyanocobalamin. AdoCbl and hydroxycobalamin are the most frequent types, followed by MeCbl (Farquharson and Adams 1976). Nevertheless both AdoCbl and MeCbl are light-sensitive, with light evoking a photodissociation of the Co C bond. The naturally found hydroxycobalamin is the product of photolysis of the light-sensitive cobalamins (Farquharson and Adams 1976 Seetharam and Alpers 1982). 

Three Automated Platforms Reacts Differently Towards Changes in Sample Type. This section describes the design of assays for cobalamin from the three main players in automated cobalamin analysis on human serum (Abbott, Bayer Diagnostics and Roche) and demonstrates how these assays react if employed for the measurement of cobalamin in human milk. Human milk contains up to 200-fold more haptocorrin than serum and most of it is unsaturated with cobalamin. If haptocorrin is insufficiently denatured, it can interfere in the assays (Lildballe et al. 2009). 

We discovered these analytical problems when seeking to analyse the content of cobalamin in human milk (Lildballe et al. 2009). However, we encountered the same problem for serum samples with a high content of unsaturated haptocorrin (Lildballe et al. 2011). Once such a problem is realized, it is possible to... 

False levels of cobalamin may be encountered if the concentration of cobalamin unsaturated haptocorrin is high as observed in human milk. 

Cobalamin, like other vitamins, is an essential micronutiient that humans obtain from food sources. Cobalamins are synthesized by microorganisms and enter the food chain through animals eating such organisms. Thus, the main sources of cobalamin are animal-derived food items including meat, fish, milk and eggs (Chanarin 1969). Plants have cobalamin-independent enzymes and do not contain the vitamin. Therefore, vegans do not receive a sufficient intake of cobalamin. 

Lildballe, D.L., Hardlei, T.F., Allen, L.H., and Nexo, E., 2009. High concentrations of haptocorrin interfere with routine measurement of cobalamins in human serum and milk. A problem and its solution. Clinical Chemistry and Laboratory Medicine. 47 182-187. 

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