Folate Metabolism in Newborns and during Early Infancy: I. Absorption of Pteroylglutamic (Folic) Acid in Newborns

Abstract

ExtractFolic acid (PGA) absorption (40 ,«g/kg of body weight) was studied in normal newborns and adults using Lactobacillus casei and Streptococcus faecalis microbiological assays for folate determination. The PGA was given orally or intramuscularly to the subjects after either saturating their tissues with folate or without prior saturation of their tissues. Without prior saturation of the tissues the folic acid absorption curves in newborns were much lower than those found in adults (figs. 1 and 2). Saturation of the tissues of the newborns with folic acid, prior to administration of the oral test dose, raised the absorption curves of the folic acid, but these were still lower than those seen in adults (fig: 5). The folate curve of the newborns after an intramuscular test dose of PGA was also lower than that observed in adults (fig. 3); however, after saturating the tissues of the newborns with folic acid, the folate curve became comparable to that of the unsaturated adults ( fig. 4).After the oral test dose, newborns excreted a much smaller percentage of the administered dose in their urine than did the adults (table II). When the tissues in newborns were saturated with folic acid, however, the excretion of folate in the urine became comparable to that of unsaturated adults (table II) These data indicate that: 1) plasma clearance of folate in newborns is more rapid than that in adults and that large saturating doses of folic acid are needed to reduce this clearance rate; and 2) the folate absorption curve in the newborn is lower than in the adult. With the criteria set for adults, this could be interpreted as evidence of impaired folate absorption in newborns. The proper interpretation of the data indicates, however, that folate absorption by newborns is slower than seen in adults and that the net absorption is comparable to that of adults. SpeculationIn newborns, the absorption curve for orally administered folate is lower than in adults. Our study indicates that this is due to the slower absorption of folates and more rapid tissue uptake of folates by newborns. Further studies should be carried out to investigate the absorption of folate conjugates which are the main forms of folate found in food, to determine how much of the folate in food is available to newborns and small infants, and to evaluate the need for supplementary folate in small infants. SHOJANIA and HORNADY 413

Folate Metabolism in Newborns and during Early Infancy: II. Clearance of Folic Acid in Plasma and Excretion of Folic Acid in Urine by Newborns

“…Although the number of subjects studied was too small for statistical evaluation, it appeared that the newborns tended to excrete a lesser percentage of the administered folale in their urine. Table 1 also shows excretion rales in three premature infants lor comparison with those of full-term infants and adults and also for comparison witli the reported data [21 ).…”

“…was any block in the utilization of folic acid in the newborn period when the folate level in serum was very Reported studies [21] have shown that the peak folate high [5,9,16,20]. level in serum after an intramuscular dose of PGA was lower in newborns than in adults, suggesting a more rapid clearance of folic acid in the newborn infant.…”

“…A period of 6-h was chosen because it was easier and more practical in the newborns. The intramuscular route was chosen in preference to the intravenous route because of ease of administration and because data for intramuscular PGA were needed for another project [21]. Adults emptied their bladder and then received the test dose of PGA.…”

“…The technique of blood collection and urine. They were also designed to see whether there the source of folic acid for standard and test doses have been described [21]. The PGA was administered to the adults through an antecubital vein; all blood samples for study were taken from the opposite arm.…”

Suplemento de acido fólico: ¿Prevención de anemia en prematuros?

“…La leche humana y de vaca en polvo reconstituida contienen aproximadamente 50 jig/litro (3,5). Toda leche es por lo tanto pobre en acido folico y esta parece ser la explication para la baja de las concentraciones sanguineas de folato en los primeros meses de la vida, las cuales aumentan cuando se aporta acido folico en las verduras (12,15 (5,6,10,13), pudiendo darse por la via oral ya que su absorcion en los recien nacidos prematuros es suficiente (6,13,14). El deficit de acido folico produce aumento de megaloblastos en la medula y anemia de tipo predominantemente macrocitico.…”