EFFECT OF AGE ON THE INTESTINAL-ABSORPTION OF VITAMIN-D-3-PALMITATE AND NONESTERIFIED VITAMIN-D-2 IN THE TERM HUMAN INFANT

This study was undertaken to investigate the utility of vitamin D-3-pa lmitate as a nutritional supplement and thus define the intestinal abs orption profile of vitamin D-2 and vitamin D-3 liberated after its cle avage from vitamin D-3-palmitate in the human infant at various postna tal ages. The subjects for study consisted of 48 normal infants that w ere simultaneously administered 0.07 and 0.08 mu mol/kg BW vitamin D a s vitamin D-3-palmitate and nonesterified vitamin D-2, respectively, b y orogastric tube. Blood samples were obtained before and 6, 12, and 2 4 h postadministration and analyzed simultaneously for vitamins D-2 an d D-3. For data analysis, the infants were divided into two groups bas ed on postnatal age: group 1, 1 day of age; and group 2, more than 10 days of age. Data were analyzed using the integrated peak area under t he absorption curve for each subject. All subjects demonstrated the ab ility to absorb vitamin D after oral administration, although postnata l age as well as vitamin form had a profound effect on the absorption of vitamin D-2 and vitamin D-3 liberated from vitamin D-3-palmitate. N onesterified vitamin D-2 is well absorbed both in very young and older infants, although absorption efficiency increases with age, perhaps d ue to increased bile acid secretion. Liberation of vitamin D-3 from vi tamin D-3-palmitate was shown to increase, perhaps due to gastrointest inal tract maturation, beyond 10 days of age, probably coinciding with the secretion of intestinal esterases. Our data indicate that both fo rms of the orally administered vitamin approach equivalency in their a bilities to elevate circulating vitamin D levels in the human infant a t a postnatal age of approximately 89 days. Thus, vitamin D-3-palmitat e would appear not to be dietarily equivalent to free vitamin D as a n utritional source of vitamin D in the human neonate.