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

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. Aim: 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. Methods: 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. Results: 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. Conclusion: 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.