Influence of vitamin B-6 intake on vitamin B-6 status of lactating women and on the vitamin content of their milk: enzymatic, microbiological, and HPLC techniques

Abstract

The influence of vitamin B-6 intake on vitamin B-6 status and the concentration of B-6 vitamers in milk of 21 white lactating women (21 to 35 years) was examined at 3 to 7 months postpartum. None of the women met the RDA for lactating women of 2.5 mg/day when considering vitamin B-6 intakes from food sources alone. All subjects taking vitamin B-6 supplements had adequate vitamin B-6 status as determined by coenzyme stimulation of erythrocyte alanine aminotransferase activity; all subjects not taking vitamin B-6 supplements had inadequate vitamin B-6 status. Plasma pyridoxal 5-phosphate values were significantly higher for subjects in the supplemented than in the nonsupplemented group. Pyridoxal, pyridoxamine, pyridoxine, and total vitamin B-6 concentrations in milk were higher, sometimes significantly, in the supplemented than in the unsupplemented group as determined by microbiological assay and HPLC. There were significant correlations between data obtained by the microbiological and HPLC analyses for pyridoxal and total vitamin B-6 concentrations. Pyridoxal was the predominant B-6 vitamer found in human milk. Distribution of the B-6 vitamers appeared to stay relatively constant despite vitamin B-6 status.