Vitamin D and mineral metabolism in the very low birth weight infant recelv ' i ng 400 IU of vitamin D Richard C o o k e , MD, Bruce Hollis, MD, C y n t h i a C o n n e r , RN, D o n n a W a t s o n , RN, Susan W e r k m a n , RN, a n d Russell C h e s n e y , MD From the Departments of Pediatrics and Obstetrics and Gynecology, University of Tennessee, Memphis, and the Department of Pediatrics, Medical University of South Carolina, Charleston

Study objective: To e x a m i n e (I) the effect of vitamin D intake (380 to 480 IU daily) on plasma 25-hydroxyvitamin D (25-0HD) and 1,25-dihydroxyvitamin D (I,25[OH]2D) concentrations and (2) the relationship of 1,25-(OH)2D to calcium and phosphorus absorption and retention in the very low birth weight infant receiving a preterm infant formula. Subjects: Eleven " w e l l " infants with a birth weight and gestational a g e (mean _+ SD) of 1,078 _+ 128 gm and 29 • 1.9 weeks, respectively, were studied for a 3-week period. Weight and postnatal a g e (mean _+ SD) at the beginning of the study were 1132 • 56 gm and 16 • 6 days, respectively. All infants were fed a preterm infant formula and tolerated a full enteral intake (120 k c a l / k g / d a y ) for the duration of the study. Interventions: Plasma 25-0HD and 1,25-(OH)2D concentrations were measured at the beginning of the study and at the beginning of e a c h 48-hour b a l a n c e period. Calcium and phosphorus b a l a n c e studies (n = 33) were performed weekly. Main results: Plasma 25-0HD (30 _+ 10 ng/ml) and 1,25-(OH)2D (54 _+ 14 p g / m l ) concentrations were normal at the beginning of the study. Plasma 25-0HD values did not c h a n g e , but 1,25-(OH)2D values increased (p