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J Pediatr Gastroenterol Nutr. 1986 Mar-Apr;5(2):278-82.

Forms of human milk folacin and variation patterns.


The pattern of folacin in 180 human milk samples collected from 16 women was studied before and after pteroylglutamic hydroxylase (conjugase) treatment. The differential response of Lactobacillus casei versus Streptococcus faecalis distinguishes N-5-methyltetrahydrofolate from other forms. Growth of Pediococcus cerevisiae differentiates the reduced monoglutamates, other than the N-5-methylated derivative, from oxidized folacins. Mean folacin activity with L. casei was 85.3 ng/ml. Prior to conjugase treatment of samples, mean activity was 46.9 ng/ml with this organism. The responses of S. faecalis and P. cerevisiae were 48% and 7.6%, respectively, of the total L. casei active folacins. The total L. casei active folacins increased from 76.5 ng/ml at 6 weeks of lactation to 97.1 ng/ml at 12 weeks of lactation. Increases were also observed with time of day: from morning (65.7 ng/ml), to afternoon (80.0 ng/ml), and to evening (114.7 ng/ml). Hindmilk had greater total L. casei activity (100.0 ng/ml) than foremilk (73.8 ng/ml). Although folacins active for S. faecalis and P. cerevisiae were not affected by duration of lactation, increases in folacin activity with time of day and from fore- to hindmilk were observed using both of these organisms. Values for the folacin content of human milk are therefore dependent on sampling procedures. Pteroylpolyglutamates of greater than or equal to 3 glutamic acid residues and N-5-methyltetrahydrofolate are the predominant forms of human milk folacin based on differential growth responses of L. casei, S. faecalis, and P. cerevisiae to these forms.

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