Vitamin D status of preterm infants at 4 months past hospital discharge : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Nutrition and Dietetics, Massey University, Albany, New Zealand

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Preterm birth and survival rates are increasing in New Zealand and around the world. Preterm infants are subject to shorter gestational lengths and subsequently suffer from decreased nutrient accretion in utero. Vitamin D is one nutrient that is accrued in the final stages of gestation. At birth preterm infants rely on an exogenous source of this nutrient to achieve and maintain adequate stores. The vitamin D status of preterm infants after hospital discharge in New Zealand was previously unknown. The aim of this study was to investigate the serum 25-hydroxyvitamin D (25(OH)D) status of preterm infants at 4 months post hospital discharge, and describe the factors affecting these concentrations. An observational study of 49 preterm infants (<37 weeks gestation) at 4 months post hospital discharge was undertaken. A capillary blood sample was obtained from infants. Serum 25(OH)D was analysed using ADIVA Centaur Vitamin D Total immunoassay. Questionnaires were used to assess sun exposure behaviours and feeding and supplement use. In this sample of 49 preterm infants, 28.6% were classified as having insufficient vitamin D status (25(OH)D ≤50 nmol/L), of these 8.2% were further classified as having mild to moderate vitamin D deficiency (25(OH)D ≤25 nmol/L). The mean 25(OH)D concentration was 73.8 nmol/L, the range was 16 nmol/L – 314 nmol/L. Vitadol C supplementation had the most significant effect on infant 25(OH)D concentrations. All (n=14) exclusively breastfed infants who did not receive Vitadol C supplements were vitamin D insufficient or deficient on analysis. All infants who received Vitadol C or infant formula were vitamin D sufficient. Vitamin D deficiency is prevalent in exclusively breastfed preterm infants not receiving vitamin D supplements. Vitamin D supplementation should be considered for all preterm infants as part of New Zealand’s child health policy.
Premature infants, Vitamin D deficiency, Vitamin D supplementation, Preterm infants, Vitamin D in infants