Longitudinal study of vitamin D status in the 1st 6 months of life

Abstract

Although hypovitaminosis D has been reported in the neonatal period and infancy, there is currently little information on the longitudinal changes in vitamin D status throughout early infancy. To estimate, in Al Ain, UAE, the prevalence of vitamin D deficiency and longitudinal changes and risk factors in infants between birth and 6 months of age. Serum 25-OH-vitamin-D levels were measured after birth and 6 months later in 27 infants of mothers of Middle Eastern or Asian origin who were pregnant between the months of September and November 2007. At delivery, mean (SD) maternal serum 25-OH-vitamin-D level was 35.5 nmol/L (24.7); five mothers (22%, 95% CI 0.7-43) had adequate serum levels (>50 mmol/L), 11 (48%, 95% CI 27-70) insufficient levels (25-50 nmol/L) and seven (30%, 95% CI 13-53) deficient (<25 nmol/L) levels. Serum 25-OH-vitamin-D levels were adequate in eight infants (30%, CI 14-50%), insufficient in 13 (48%, CI 28-60%) and deficient in six (22%, CI 8.5-42%). Despite recommendations, none had received any vitamin D supplementation since birth. Despite the high prevalence of hypovitaminosis D at birth and the lack of pharmacological supplementation, the number of infants with adequate levels at 6 months of age rose to 20 (87%, CI 66-97%). No infant had deficiency (CI 0-21%) and three (13%, CI 27-33%) had insufficiency. Adequate levels were detected in four infants who were partially breastfed [mean (SD) 108.5 (20.7) nmol/L] and in only 84% of the 19 exclusively breastfed infants [mean (SD) 96.2 (44.5) nmol/L] but the difference was not statistically significant. Although serum levels improved at 6 months, it occurred more slowly in exclusively breastfed infants. In the absence of vitamin D supplementation, guidelines for vitamin D supplementation in infancy still need to be followed because the mechanisms for normalisation are not clearly understood.