Vitamin B-6 adequacy in neonatal nutrition: associations with preterm delivery, type of feeding, and vitamin B-6 supplementation.

Concerns about vitamin B-6 adequacy in neonatal nutrition relate to critical functions of the vitamin in development. Vitamin B-6 status was assessed in six groups of neonates: two groups each of breast-fed term and preterm infants whose mothers were supplemented with 2 or 27 mg pyridoxine-hydrochloride (PN-HCl); a subgroup of term infants (2-mg maternal group) supplemented with 0.4 mg PN-HCl/d; and a formula-fed preterm group. During the 28-d experimental period, weekly assessments showed lower concentrations of total vitamin B-6 and percentages of pyridoxal in milk from mothers of preterm infants than in milk from mothers of term infants, even when maternal PN-HCl supplementation was 27 mg/d. The vitamin B-6 concentration of milk and estimated intakes of the vitamin by breast-fed infants paralleled maternal supplements (ie, 2 and 27 mg). Plasma and erythrocyte measurements of infants correlated with their vitamin B-6 intakes; values were highest for infants given vitamin B-6 supplements and those that wee formula-fed. Vitamin B-6 adequacy was questionable for unsupplemented breast-fed infants of mothers in the 2-mg supplemented groups.

Influence of vitamin B6 intake on the content of the vitamin in human milk.

The influence of the level of vitamin B6 intake on the content of the vitamin in milk was studied in 19 healthy subjects whose stages of lactation ranged from 3 weeks to 30 months. Total vitamin B6 intakes, including extra-dietary sources of the vitamin, ranged from 1.3 to 12.5 mg per day with six subjects consuming less than the recommended allowance of 2.5 mg per day (RDA, 1974). Subjects consuming less than 2.5 mg of vitamin B6 per day had significantly less vitamin B6/liter milk (129 mug) than groups consuming 2.5 to 5.0 or greater than 5.0 mg per day (239 and 314 mug, respectively). Among subjects consuming greater than 2.5 mg of vitamin per day the stage of lactation did not influence the levels of protein or vitamin B6 in milk. Vitamin B6 intakes two to five times the recommended allowance did not significantly elevate the level of the vitamin in milk compared to values for subjects whose intakes approximated the allowance. The vitamin B6/protein ratio in milk of subjects consuming less than 2.5 mg vitamin B6 per day was 13 mug/g and was significantly lower than that observed for the other two groups (23 and 28 mug/g). Daily and weekly variations of the vitamin B6 and protein content in milk of individuals were small. However, marked diurnal variations in the vitamin B6 content were found in milk of individuals taking daily supplements of the vitamin with peak levels occurring in the afternoon 3 to 5 hr after supplements were taken in the morning.