What is human milk?  Fact-checking a nutrition website.

 The following was caused by the fact that modifying nouns with an adjective describing their intended use can be confused with using an adjective describing their source.  However, it seems that "human milk" is universally used to describe milk which humans are the source of, and not a fluid fed to human infants as a substitute.  The abstract as it appears on this website contains both of the following statements:
"Sialic acid is present in human milk ...it is yet another constituent that might beneficially be added to human milk."

                                                                                    [Source: Wang B, et al. Am J Clin Nutr 2001;74:510-5]

So I wrote to the content editor of the website and expressed my puzzlement:


  Hello:  I found this on your website http://www.everybody.co.nz/nutrition/nnoct10_01sialic.html.  Although I am excited about the new information, I am puzzled by the conclusion.  Sialic acid doesn't seem to need to be added, since human milk is already a rich source, and furthermore adding anything to the breast is problematic.  Except in unusual circumstances, expressing breastmilk in order to add things to it is not the normal recommended method of breastfeeding.  Is the sentence worded correctly?  

  Arly Helm, MS, IBCLC

  His answer came right away, and I hope they clear up the problem on their website as quickly:

Thanks for this question. This summary from John Birkbeck can also be checked as an online abstract at NCBI MedLine, and having just had a look I think it probably means that sialic acid might usefully be added by the manufacturers of human formula, not for mothers to add it to breastmilk.

Sorry this was not clearer.

Richard French 
[log in to unmask] 

I followed Richard French's suggestion and looked at the abstract on Medline.  The actual conclusion is:  

Human milk, including milk from mothers of preterm infants, is a rich source of oligosaccharide-bound sialic acid, which contrasts with the relatively small amounts found in infant formulas. 

So in the original, a distinction was made.  Wang et al. have published other studies on sialic acid, and they do not refer to commercial formula as human milk. 

"We found that the saliva of preterm infants fed human milk contains twice the level of sialic acid as that in infants fed commercial formulas. The higher sialic acid level suggests greater viscosity and enhanced protection of the mucosal surfaces in breast-fed infants. Human milk itself is a rich source of sialylated oligosaccharides."

Wang B, Miller JB, Sun Y, Ahmad Z, McVeagh P, Petocz P.A longitudinal study of salivary sialic acid in preterm infants: Comparison of human milk-fed versus formula-fed infants.J Pediatr. 2001 Jun;138(6):914-6.

Other authors writing on sialic acid have made the same distinction:

"...Because the brain and central nervous system contain considerable level of sialic acid in infancy, it is considered to play important roles on the expression and development of their functions. Moreover, we found that some sialylated compounds had inhibited the adhesion of toxins, bacteria and viruses to the receptors on the surface of epithelial cells. Additionally, we found that some sialylated compounds had growth-promoting effects on bifidobacteria and lactobacilli, predominantly present in the intestinal flora of infants fed with human milk. The results suggested that sialylated compounds in human milk possibly behaved as a physiological component in the intestinal tract of infants to protect them against enteric infections."  Nakano T, Sugawara M, Kawakami H.  Sialic acid in human milk: composition and functions.
Acta Paediatr Taiwan 2001 Jan-Feb;42(1):11-7.

I would like to thank John Birkbeck for highlighting this research, but also suggest his summary be amended to eliminate the incorrect use of the term "human milk" for infant formula.











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