Do all infants need vitamin D supplementation?

A high prevalence of vitamin D deficiency (VDD) in children has been observed worldwide, but there are few studies on the nutritional status of vitamin D (VD) in healthy infants. The main cause of deficiency in healthy children is breastfeeding without supplementation and lack or insufficiency of sun exposure. The aims of this study were to determine serum concentrations of 25(OH)D and verify its association with parathyroid hormone (PTH) concentrations and use of VD supplementation in healthy infants aged ≥ 6 to ≤ 24 months attended at two Primary Health Care Units in Ribeirão Preto city, São Paulo, Brazil. A cross-sectional, observational and analytical study was performed in which serum concentrations of 25(OH)D, PTH, alkaline phosphatase (AP), calcium (Ca), phosphorus (P) and albumin were determined in 155 healthy infants. Information on sun exposure, sociodemographic aspects of mothers and clinical and nutritional characteristics of infants were obtained through interviews with responsible infants's legal representatives. Ten infants (6%) presented deficient 25(OH)D serum concentration (≤20ng/ml) and 46 (30%), insufficient (21 to 29ng/ml). No changes in serum P, Ca and albumin concentrations were detected. Only one infant had an increase in PTH serum concentrations. 35% (55/155) of infants had high AP e 40% (22/55) presented insufficient serum concentrations of 25(OH)D but none presented deficient ones. There was a weak association between serum concentrations of 25(OH)D and PTH and an association between serum concentrations of 25(OH)D and P when adjusted for sex, age and BMI. There were no associations between inadequate serum concentrations of 25(OH)D (deficient ou insufficient), sun exposure and VD supplementation. This study found a low prevalence of deficient 25(OH)D serum concentration and high prevalence of insufficient ones which was not associated with changes in serum PTH, AP, P, Ca and albumin concentrations, VD supplementation and the formula volume intake.